CN113690927A

CN113690927A - Power supply system and fault identification method of group string thereof

Info

Publication number: CN113690927A
Application number: CN202110780337.9A
Authority: CN
Inventors: 汪建强; 刘辉平; 万松; 张彦忠
Original assignee: Huawei Digital Power Technologies Co Ltd
Current assignee: Huawei Digital Power Technologies Co Ltd
Priority date: 2021-07-09
Filing date: 2021-07-09
Publication date: 2021-11-23

Abstract

The application provides a power supply system and a fault identification method of a group string of the power supply system. The sampling device acquires a plurality of working parameters of the first group of strings at a plurality of sampling voltage moments to obtain a plurality of groups of sampling data of a first sampling time period, and sends the plurality of groups of sampling data of the first sampling time period to the management system. The management system receives multiple groups of sampling data of a first sampling time period, determines a working characteristic curve of a first group of strings in the first sampling time period based on the multiple groups of sampling data, and determines whether the working characteristic curve of the first group of strings in the first sampling time period is distorted according to a curvature value of a first sampling point on the working characteristic curve of the first sampling time period, so that whether the first group of strings is in fault is determined, the assembly technology is not required, and the applicability is high.

Description

Power supply system and fault identification method of group string thereof

Technical Field

The application relates to the technical field of photovoltaic power generation, in particular to a power supply system and a fault identification method of a string of the power supply system.

Background

The string is formed by connecting a plurality of photovoltaic modules or a plurality of batteries in series, a power supply system can be formed by connecting a plurality of strings in parallel, and the power supply system can be widely applied to scenes such as solar power generation, uninterrupted power supply and the like.

At present, for a fault identification mode of a string in a power supply system, characteristic parameters of the string are determined mainly according to a plurality of groups of collected current and voltage values of the string and a preset string physical model (representing a relationship between the voltage and current values of the string and the characteristic parameters of the string). Illustratively, the preset string physical model is a forward output single-diode model, i.e., I ═ I_L-I₀{exp[q*(V+IR_s)/(nkT)]-1}-(V+IR_s)/R_sh. Wherein I is the group string working current I_LFor photo-generated current (short-circuit current can be substituted in the calculation), I₀Is the saturation current of an equivalent diode in a single diode model, q is a charge constant, V is the string working voltage, R_sIs a series resistor of the battery string, n is a single-diode equivalent circuit diode ideal factor, k is a Boltzmann constant, T is the temperature of the battery string, R_shAre grouped into series-parallel resistors. Fitting characteristic parameters I of the string through a single-diode model and a plurality of groups of current and voltage values₀，n，R_sAnd R_sh. And then comparing the characteristic parameters of the string with the standard parameters, and determining whether the string is in fault according to the comparison result.

Due to the fact that technical parameters of different string manufacturing manufacturers are greatly different, the string physical model cannot be suitable for strings of all manufacturers, and the mode is high in dependence on component technology and poor in applicability.

Disclosure of Invention

The application provides a power supply system and a fault identification method of a string of the power supply system, which can determine whether a working characteristic curve is distorted or not based on analysis of the working characteristic curve of the string, thereby realizing fault identification of the string without depending on a component technology and having strong applicability.

In a first aspect, the present application provides a power supply system that includes a management system, a sampling device that establishes a communication connection with the management system, an inverter, and a first set of strings connected to the inverter. The sampling device acquires a plurality of working parameters of the first group of strings under a plurality of sampling voltages to obtain a plurality of groups of sampling data of the first sampling time period, and sends the plurality of groups of sampling data of the first sampling time period to the management system. The management system receives multiple groups of sampling data of a first sampling time period, determines a working characteristic curve of the first group of strings in the first sampling time period based on the multiple groups of sampling data of the first sampling time period, and further determines whether the working characteristic curve of the first group of strings in the first sampling time period is distorted according to a curvature value of a first sampling point on the working characteristic curve, so that whether the first group of strings is in fault is determined, the assembly technology is not required, and the applicability is high.

With reference to the first aspect, in a first possible implementation manner, because the curvature value of the working characteristic curve of the normal string is relatively gentle in variation trend, the management system may determine, when the curvature value of the first sampling point is greater than a preset curvature threshold value, that the first sampling point is a distortion point on the working characteristic curve, and further determine a string fault, thereby reducing the computational complexity and having strong applicability.

With reference to the first aspect, in a second possible implementation, the operating characteristic curve includes a first curve segment, the first curve segment is an operating characteristic curve sampled in a first sampling voltage interval, and the first curve segment includes a first sampling point. And the management system acquires a standard curve segment corresponding to the first curve segment, and the sampling voltage of each standard sampling point on the standard curve segment is the same as the sampling voltage of each sampling point on the first curve segment. And then determining the similarity between the first curve segment and the standard curve segment according to the curvature value of each sampling point on the first curve segment and the standard curvature value of each standard sampling point on the standard curve segment. And determining that the first group of strings has faults when the similarity is smaller than a preset similarity threshold. The standard curve segment is a working characteristic curve acquired by the normal string in the first voltage sampling interval, the sampling voltages of the standard sampling points on the curve segment are respectively and correspondingly the same as the sampling voltages of the sampling points on the first curve segment, and then whether the string fails or not can be determined according to the similarity between the standard curve segment and the first curve segment, so that the accuracy of string fault identification can be improved, and further, the condition of fault identification errors caused by environmental changes of a filtering part can be improved by changing the size of the preset similarity threshold value, so that the applicability is stronger.

With reference to the first aspect, in a third possible implementation manner, the working characteristic curve includes a first curve segment and a second curve segment, the first curve segment is a working characteristic curve sampled in a first sampling voltage interval, the second curve segment is a working characteristic curve sampled in a second sampling voltage interval, the first sampling voltage interval is adjacent to the second sampling voltage interval, a sampling voltage of each sampling point in the first sampling voltage interval is greater than a sampling voltage of each sampling point in the second sampling voltage interval, and the first curve segment includes the first sampling point. The management system determines a first curvature characteristic value of the first curve segment based on the curvature value of each point on the first curve segment and a second curvature characteristic value of the second curve segment based on the curvature value of each point on the second curve segment. When the first difference between the first curvature characteristic value and the second curvature characteristic value is larger than a first preset difference threshold value, the change trend (namely descending) of the curvature characteristic values of the first curve section and the second curve section is larger than the change trend (namely ascending) of the curvature characteristic values of two adjacent curve sections of the normal group of strings, and therefore the working characteristic curve of the first group of strings in the first sampling time period is determined to be distorted, the first group of strings is determined to be in fault, and the applicability is strong.

With reference to the first aspect, in a fourth possible implementation manner, the operating characteristic curve includes a first curve segment, a second curve segment and a third curve segment, the first curve segment is an operating characteristic curve sampled in a first sampling voltage interval, the second curve segment is an operating characteristic curve sampled in a second sampling voltage interval, the third curve segment is an operating characteristic curve sampled in a third sampling voltage interval, the second sampling voltage interval is adjacent to the first sampling voltage interval and the third sampling voltage interval, a sampling voltage of each sampling point in the second sampling voltage interval is greater than a sampling voltage of each sampling point in the first sampling voltage interval, and is less than a sampling voltage of each sampling point in the third sampling voltage interval, and the first curve segment includes the first sampling point. The management system determines a first curvature characteristic value of the first curve segment according to the curvature value of each point on the first curve segment, determines a second curvature characteristic value of the second curve segment according to the curvature value of each point on the second curve segment, and determines a third curvature characteristic value of the third curve segment according to the curvature value of each point on the third curve segment. When the first difference between the first curvature characteristic value and the second curvature characteristic value is smaller than a second preset difference threshold value, and the second difference between the second curvature characteristic value and the third curvature characteristic value is larger than a third preset difference threshold value, it is described that the variation trend (i.e., increasing first and then decreasing) of the curvature characteristic values of the first curve segment, the second curve segment and the third curve segment is greatly deviated from the variation trend (i.e., increasing always) of the curvature characteristic values of three adjacent curve segments of the normal group string, and it is further determined that the working characteristic curve of the first group string in the first sampling time period is distorted, so that the first group string is determined to be faulty, and the applicability is strong.

With reference to the first aspect, in a fifth possible implementation, the management system determines an average of curvature values of all sampling points on the first curve segment as the first curvature characteristic value.

With reference to the first aspect, in a sixth possible implementation manner, the curvature value of the first sampling point

Wherein, f' (U)₁) And f' (U)₁) The first derivative value and the second derivative value of the working characteristic curve of the first sampling time period at the first sampling point are respectively.

With reference to the first aspect, in a seventh possible implementation manner, the management system receives multiple sets of sampling data of a first set of strings in N sampling time periods under multiple sampling voltages, and determines a working characteristic curve of the first set of strings in each sampling time period, that is, a working characteristic curve of each sampling time period, based on the multiple sets of sampling data of each sampling time period, where the N sampling time periods include the first time period, and the N sampling time periods are different from each other, and each sampling point on the working characteristic curve of each sampling time period corresponds to each sampling voltage one to one. And then the management system determines whether the first group of strings has faults or not according to the curvature value of the first sampling point on the working characteristic curve of each sampling time period. And then except not needing to rely on the subassembly technique, still can effectively avoid because single fault identification receive environmental factor (for example cloud layer shelters from, the morning and evening solar altitude angle difference leads to the sheltering from of different degree between the cluster) and the undulant condition that leads to the cluster fault misidentification of group that influences of test equipment easily, improve the accuracy that the cluster fault detected, the suitability is stronger.

With reference to the first aspect, in an eighth possible implementation manner, the N sampling time periods include a second sampling time period, and an interval duration between the second sampling time period and the first sampling time period is greater than a preset interval duration threshold. The influence on string fault identification due to long-time environmental factor fluctuation (such as cloudy throughout the day) can be further avoided, and the accuracy of string fault detection is improved.

With reference to the first aspect, in a ninth possible implementation, the N sampling periods include N-1 third sampling periods. The management system receives multiple groups of sampling data of a first sampling time period of the first group of strings under multiple sampling voltages, determines a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period, and determines an initial working state of the first group of strings according to a curvature value of a first sampling point on the working characteristic curve of the first sampling time period. And when the initial working state is the first working state, receiving a plurality of groups of sampling data of the first group of strings under N-1 third sampling time periods. For the mode of directly obtaining a plurality of groups of sampling data of the group string in a plurality of sampling time periods, the power generation loss of the inverter connected with the group string can be reduced, and further the power generation loss of the power supply system is reduced. In addition, the accuracy of string fault detection can be improved, and the applicability is stronger.

In a second aspect, the present application provides a power supply system that includes a management system, a sampling device that establishes a communication connection with the management system, an inverter, and a first set of strings connected to the inverter. The sampling device acquires a plurality of working parameters of the first group of strings under a plurality of sampling voltages to obtain a plurality of groups of sampling data of the first sampling time period, and sends the plurality of groups of sampling data of the first sampling time period to the management system. The management system receives multiple groups of sampling data of a first sampling time period, and determines a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period, wherein the working characteristic curve of the first sampling time period comprises a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a first sampling voltage interval. And then, according to the distance deviation value from each sampling point on the first curve segment of the first sampling time period to the first straight line corresponding to the first curve segment, determining whether the working characteristic curve of the first group of strings is distorted, and further determining whether the first group of strings has a fault.

In combination with the second aspect, in a first possible implementation, the management system determines the first group of string faults when there is no second sampling point on the first curve segment, wherein the second sampling point is a boundary point of a first sub-curve segment and a second sub-curve segment, wherein the first sub-curve segment is a curve segment on the first curve segment whose sampling voltage is smaller than that of the second sampling point, and a distance deviation value of each sampling point on the first sub-curve segment increases with an increase in the sampling voltage, the second sub-curve segment is a curve segment on the first curve segment whose sampling voltage is larger than that of the second sampling point, and a distance deviation value of each sampling point on the second sub-curve segment decreases with an increase in the sampling voltage.

With reference to the second aspect, in a second possible implementation, the management system receives a plurality of sets of sampling data of a first set of N sampling time periods that are serially connected at a plurality of sampling voltages, and determines an operating characteristic curve of each sampling time period based on the plurality of sets of sampling data of each sampling time period, where the N sampling time periods include a first time period, the N sampling time periods are different from each other, the operating characteristic curve of each sampling time period includes a first curve segment of each sampling time period, and the first curve segment of each sampling time period is an operating characteristic curve obtained by sampling in a first sampling voltage interval. And determining whether the first group of strings has a fault according to the distance deviation value from each sampling point on the first curve segment of each sampling time period to the first straight line corresponding to the first curve segment of each sampling time period, wherein the first straight line corresponding to the first curve segment of each sampling time period is determined by the initial sampling point and the final sampling point of the first curve segment of each sampling time period. And then except not needing to rely on the subassembly technique, still can effectively avoid because single fault identification receive environmental factor (for example cloud layer shelters from, the morning and evening solar altitude angle difference leads to the sheltering from of different degree between the cluster) and the undulant condition that leads to the cluster fault misidentification of group that influences of test equipment easily, improve the accuracy that the cluster fault detected, the suitability is stronger.

With reference to the second aspect, in a third possible implementation, the N sampling time periods include a second sampling time period, and an interval duration between the second sampling time period and the first sampling time period is greater than a preset interval duration threshold. The influence on string fault identification due to long-time environmental factor fluctuation (such as cloudy throughout the day) can be further avoided, and the accuracy of string fault detection is improved.

With reference to the second aspect, in a fourth possible implementation, the N sampling periods include N-1 third sampling periods. The management system receives a plurality of groups of sampling data of a first sampling time period of a first group of strings under a plurality of sampling voltages, and determines a working characteristic curve of the first sampling time period based on the plurality of groups of sampling data of the first sampling time period, wherein the working characteristic curve of the first sampling time period comprises a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a first sampling voltage interval. And further determining an initial working state of the first group of strings according to the distance deviation amount from each sampling point on the first sampling time period to a first straight line corresponding to a first curve segment of the first sampling time period, and receiving multiple groups of sampling data of the first group of strings in N-1 third sampling time periods when the initial working state is the first working state. For the mode of directly obtaining a plurality of groups of sampling data of the group string in a plurality of sampling time periods, the power generation loss of the inverter connected with the group string can be reduced, and further the power generation loss of the power supply system is reduced. In addition, the accuracy of string fault detection can be improved, and the applicability is stronger.

In a third aspect, the present application provides a power supply system that includes a management system, a sampling device that establishes a communication connection with the management system, an inverter, and a first set of strings connected to the inverter. The sampling device acquires a plurality of working parameters of the first group of strings under a plurality of sampling voltages to obtain a plurality of groups of sampling data of the first sampling time period, and sends the plurality of groups of sampling data of the first sampling time period to the management system. The management system receives multiple groups of sampling data of a first sampling time period, and determines a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period, wherein the working characteristic curve of the first sampling time period comprises multiple curve segments of the first sampling time period, and each curve segment of the first sampling time period is a working characteristic curve obtained by sampling in each sampling voltage interval. The method comprises the steps of determining first-order derivative characteristic values of all curve segments of a first sampling time period, determining whether a working characteristic curve of a first group of strings in the first sampling time period is distorted according to the first-order derivative characteristic values of all the curve segments of the first sampling time period, and further determining whether the first group of strings is in fault.

With reference to the third aspect, in a first possible implementation manner, the plurality of curve segments include a first curve segment, a second curve segment and a third curve segment, where the first curve segment is an operating characteristic curve sampled in a first sampling voltage interval, the second curve segment is an operating characteristic curve sampled in a second sampling voltage interval, the third curve segment is an operating characteristic curve sampled in a third sampling voltage interval, the second sampling voltage interval is adjacent to the first sampling voltage interval and the third sampling voltage interval, and a sampling voltage of each sampling point in the second sampling voltage interval is greater than a sampling voltage of each sampling point in the first sampling voltage interval and is less than a sampling voltage of each sampling point in the third sampling voltage interval. The management system determines whether the first group of strings are in fault according to a sixth difference value between the first-order derivative characteristic value of the first curve segment and the first-order derivative characteristic value of the second curve segment and a seventh difference value between the first-order derivative characteristic value of the second curve segment and the first-order derivative characteristic value of the third curve segment, namely, group string fault identification can be performed according to the variation trend of the first-order derivative characteristic values of three adjacent curve segments, and the group string fault identification accuracy is improved by improving the number of the analyzed curve segments.

With reference to the third aspect, in a second possible implementation manner, when the ratio between the sixth difference and the seventh difference is greater than a preset ratio threshold, the management system indicates that distortion occurs in the first curve segment, the second curve segment, and the third curve segment, so as to determine the first group of string faults, and perform group string fault identification from a global perspective, which is higher in accuracy and stronger in applicability. Furthermore, the fault identification of the group strings in different degrees can be realized by changing the size of the preset ratio threshold value, and the flexibility is high.

With reference to the third aspect, in a third possible implementation manner, when the sixth difference is greater than a seventh preset difference threshold and the seventh difference is less than an eighth preset difference threshold, the management system indicates that a variation trend (i.e., decreasing first and then increasing) of the first-order derivative characteristic values of the first curve segment, the second curve segment, and the third curve segment is greatly deviated from a variation trend (i.e., decreasing always) of the first-order derivative characteristic values of three adjacent curve segments of the normal string set, and further determines that the working characteristic curve of the first string is distorted, thereby determining that the first string has a fault, and the applicability is strong. Furthermore, the fault identification of the group strings in different degrees can be realized by changing the size of the seventh preset difference threshold and/or the eighth preset difference threshold, and the flexibility is high.

With reference to the third aspect, in a fourth possible implementation, the management system determines a first derivative value of each sampling point on each curve segment, and determines an average of the first derivative values of all the sampling points on each curve segment as a first derivative characteristic value of each curve segment. The accuracy of fault identification of the string can be improved by defining the first derivative characteristic values of the curve segments with the mean value.

With reference to the third aspect, in a fifth possible implementation, the management system receives a first group of sets of sampling data of N sampling time periods that are serially connected at multiple sampling voltages, and determines an operating characteristic curve of each sampling time period based on the sets of sampling data of each sampling time period, where the N sampling time periods include the first time period, the N sampling time periods are different from each other, the operating characteristic curve of each sampling time period includes multiple curve segments of each sampling time period, and each curve segment of each sampling time period is an operating characteristic curve obtained by sampling in each sampling voltage interval. And further determining the first derivative characteristic value of each curve segment of each sampling time period, and determining whether the first group of strings have faults or not according to the first derivative characteristic value of each curve segment of each sampling time period. And then except not needing to rely on the subassembly technique, still can effectively avoid because single fault identification receive environmental factor (for example cloud layer shelters from, the morning and evening solar altitude angle difference leads to the sheltering from of different degree between the cluster) and the undulant condition that leads to the cluster fault misidentification of group that influences of test equipment easily, improve the accuracy that the cluster fault detected, the suitability is stronger.

With reference to the third aspect, in a sixth possible implementation, the N sampling time periods include a second sampling time period, and an interval duration between the second sampling time period and the first sampling time period is greater than a preset interval duration threshold. The influence on string fault identification due to long-time environmental factor fluctuation (such as cloudy throughout the day) can be further avoided, and the accuracy of string fault detection is improved.

With reference to the third aspect, in a seventh possible implementation, the N sampling periods include N-1 third sampling periods. The management system receives a plurality of groups of sampling data of a first sampling time period of a first group of strings under a plurality of sampling voltages, and determines a working characteristic curve of the first sampling time period based on the plurality of groups of sampling data of the first sampling time period, wherein the working characteristic curve of the first sampling time period comprises a plurality of curve segments of the first sampling time period. And determining an initial working state of the first group of strings according to the first derivative characteristic values of all curve segments of the first sampling time period, and receiving a plurality of groups of sampling data of the first group of strings in the N-1 third sampling time periods when the initial working state is the first working state. For the mode of directly obtaining a plurality of groups of sampling data of the group string in a plurality of sampling time periods, the power generation loss of the inverter connected with the group string can be reduced, and further the power generation loss of the power supply system is reduced. In addition, the accuracy of string fault detection can be improved, and the applicability is stronger.

In a fourth aspect, the present application provides a power supply system that includes a management system, a sampling device that establishes a communication connection with the management system, an inverter, and a first set of strings connected to the inverter. The sampling device acquires a plurality of working parameters of the first group of strings under a plurality of sampling voltages to obtain a plurality of groups of sampling data of the first sampling time period, and sends the plurality of groups of sampling data of the first sampling time period to the management system. The management system receives multiple groups of sampling data of a first sampling time period, determines a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period, and each sampling point on the working characteristic curve of the first sampling time period corresponds to each sampling voltage one by one. And then, determining whether the working characteristic curve of the first group of strings in the first sampling time period is distorted according to the second derivative value of the third sampling point on the working characteristic curve of the first sampling time period, and further determining whether the first group of strings has faults or not without depending on an assembly technology, so that the applicability is high.

With reference to the fourth aspect, in a first possible implementation manner, when the second derivative value of the third sampling point is 0, the management system determines that the point is a distortion point of the first group of strings on the working characteristic curve of the first sampling time period, and further determines that the first group of strings has a fault, so that the computation complexity can be reduced, and the applicability is strong.

With reference to the fourth aspect, in a second possible implementation manner, the management system receives a plurality of sets of sampling data of a first set of sampling time periods that are serially connected to the plurality of sampling voltages, and determines an operating characteristic curve of each sampling time period based on the plurality of sets of sampling data of each sampling time period, where the N sampling time periods include the first time period, the N sampling time periods are different from each other, and each sampling point on the operating characteristic curve of each sampling time period corresponds to each sampling voltage one to one. And then determining whether the first group of strings are in failure according to the second derivative value of the third sampling point on the working characteristic curve of each sampling time period. And then except not needing to rely on the subassembly technique, still can effectively avoid because single fault identification receive environmental factor (for example cloud layer shelters from, the morning and evening solar altitude angle difference leads to the sheltering from of different degree between the cluster) and the undulant condition that leads to the cluster fault misidentification of group that influences of test equipment easily, improve the accuracy that the cluster fault detected, the suitability is stronger.

With reference to the fourth aspect, in a third possible implementation, the N sampling time periods include a second sampling time period, and an interval duration between the second sampling time period and the first sampling time period is greater than a preset interval duration threshold. The influence on string fault identification due to long-time environmental factor fluctuation (such as cloudy throughout the day) can be further avoided, and the accuracy of string fault detection is improved.

With reference to the fourth aspect, in a fourth possible implementation, the N sampling periods include N-1 third sampling periods. The management system receives a plurality of groups of sampling data of a first sampling time period of a first group of strings under a plurality of sampling voltages, and determines a working characteristic curve of the first sampling time period based on the plurality of groups of sampling data of the first sampling time period. And then determining the initial working state of the first group of strings according to the second derivative value of the third sampling point on the working characteristic curve of the first sampling time period, and receiving multiple groups of sampling data of the first group of strings in N-1 third sampling time periods when the initial working state is the first working state. For the mode of directly obtaining a plurality of groups of sampling data of the group string in a plurality of sampling time periods, the power generation loss of the inverter connected with the group string can be reduced, and further the power generation loss of the power supply system is reduced. In addition, the accuracy of string fault detection can be improved, and the applicability is stronger.

In a fifth aspect, the present application provides a method for identifying a fault in a string set, the method being applicable to a power supply system including a sampling device, an inverter, and a first string set connected to the inverter. The management system receives multiple groups of sampling data of a first sampling time period of a first group of strings under multiple sampling voltages, the multiple groups of sampling data of the first sampling time period are sent by the sampling device, a working characteristic curve of the first sampling time period is determined based on the multiple groups of sampling data of the first sampling time period, and whether the working characteristic curve of the first group of strings in the first sampling time period is distorted or not is determined according to a curvature value of a first sampling point on the working characteristic curve of the first sampling time period, so that whether the first group of strings are in fault or not is determined.

With reference to the fifth aspect, in a first possible implementation manner, the management system may determine that the first sampling point is a distortion point on the working characteristic curve of the first sampling time period when the curvature value of the first sampling point on the working characteristic curve of the first sampling time period is greater than a preset curvature threshold value, and then determine that the string fault occurs.

With reference to the fifth aspect, in a second possible implementation, the operating characteristic includes a first curve segment, the first curve segment is an operating characteristic sampled in a first sampling voltage interval, and the first curve segment includes a first sampling point. The management system acquires a standard curve segment corresponding to the first curve segment, and the sampling voltages of a plurality of standard sampling points on the standard curve segment are respectively corresponding to the same sampling voltages of a plurality of sampling points on the first curve segment. And then determining the similarity between the first curve segment and the standard curve segment according to the curvature value of each sampling point on the first curve segment and the standard curvature value of each standard sampling point on the standard curve segment. And determining that the first group of strings has faults when the similarity is smaller than a preset similarity threshold.

With reference to the fifth aspect, in a third possible implementation manner, the operating characteristic curve includes a first curve segment and a second curve segment, the first curve segment is an operating characteristic curve sampled in a first sampling voltage interval, the second curve segment is an operating characteristic curve sampled in a second sampling voltage interval, the first sampling voltage interval is adjacent to the second sampling voltage interval, and the sampling voltage of each sampling point in the first sampling voltage interval is greater than the sampling voltage of each sampling point in the second sampling voltage interval, and the first curve segment includes the first sampling point. The management system determines a first curvature characteristic value of the first curve segment based on the curvature value of each point on the first curve segment and a second curvature characteristic value of the second curve segment based on the curvature value of each point on the second curve segment. And when a first difference value between the first curvature characteristic value and the second curvature characteristic value is larger than a first preset difference threshold value, determining that the working characteristic curve of the first group of strings in the first sampling time period is distorted, and determining that the first group of strings has faults.

With reference to the fifth aspect, in a fourth possible implementation manner, the operating characteristic curve includes a first curve segment, a second curve segment and a third curve segment, the first curve segment is an operating characteristic curve sampled in a first sampling voltage interval, the second curve segment is an operating characteristic curve sampled in a second sampling voltage interval, the third curve segment is an operating characteristic curve sampled in a third sampling voltage interval, the second sampling voltage interval is adjacent to the first sampling voltage interval and the third sampling voltage interval, the sampling voltage of each sampling point in the second sampling voltage interval is greater than the sampling voltage of each sampling point in the first sampling voltage interval, and is less than the sampling voltage of each sampling point in the third sampling voltage interval, and the first curve segment includes the first sampling point. The management system determines a first curvature characteristic value of the first curve segment according to the curvature value of each point on the first curve segment, determines a second curvature characteristic value of the second curve segment according to the curvature value of each point on the second curve segment, and determines a third curvature characteristic value of the third curve segment according to the curvature value of each point on the third curve segment. And when a first difference value between the first curvature characteristic value and the second curvature characteristic value is smaller than a second preset difference threshold value, and a second difference value between the second curvature characteristic value and the third curvature characteristic value is larger than a third preset difference threshold value, determining that the working characteristic curve of the first group of strings in the first sampling time period is distorted, and determining that the first group of strings is in fault.

With reference to the fifth aspect, in a fifth possible implementation, the management system determines an average of curvature values of all sampling points on the first curve segment as the first curvature characteristic value.

With reference to the fifth aspect, in a sixth possible implementation manner, the curvature value of the first sampling point

With reference to the fifth aspect, in a seventh possible implementation manner, the management system receives multiple sets of sampling data of the first set of strings in N sampling time periods under multiple sampling voltages, and determines an operating characteristic curve of the first set of strings in each sampling time period, that is, an operating characteristic curve of each sampling time period, based on the multiple sets of sampling data of each sampling time period, where the N sampling time periods include the first time period, and the N sampling time periods are different from each other, and each sampling point on the operating characteristic curve of each sampling time period corresponds to each sampling voltage one to one. And then the management system determines whether the first group of strings has faults or not according to the curvature value of the first sampling point on the working characteristic curve of each sampling time period.

With reference to the fifth aspect, in an eighth possible implementation manner, the N sampling time periods include a second sampling time period, and an interval duration between the second sampling time period and the first sampling time period is greater than a preset interval duration threshold.

With reference to the fifth aspect, in a ninth possible implementation, the N sampling periods include N-1 third sampling periods. The management system receives multiple groups of sampling data of a first sampling time period of the first group of strings under multiple sampling voltages, determines a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period, and determines an initial working state of the first group of strings according to a curvature value of a first sampling point on the working characteristic curve of the first sampling time period. And when the initial working state is the first working state, receiving a plurality of groups of sampling data of the first group of strings under N-1 third sampling time periods.

In a sixth aspect, the present application provides a method for identifying a fault in a string set, the method being applied to a power supply system including a sampling device, an inverter, and a first string set connected to the inverter. The management system receives a plurality of groups of sampling data of a first sampling time period of a first group of strings under a plurality of sampling voltages, which are sent by a sampling device, and determines a working characteristic curve of the first sampling time period based on the plurality of groups of sampling data of the first sampling time period, wherein the working characteristic curve of the first sampling time period comprises a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a first sampling voltage interval. And then determining whether the working characteristic curve of the first group of strings is distorted according to the distance deviation value from each sampling point on the first curve segment of the first sampling time period to the first straight line corresponding to the first curve segment, and further determining whether the first group of strings is in fault.

With reference to the sixth aspect, in a first possible implementation, the management system determines the first group of string faults when there is no second sampling point on the first curve segment, wherein the second sampling point is a boundary point of a first sub-curve segment and a second sub-curve segment, wherein the first sub-curve segment is a curve segment on the first curve segment whose sampling voltage is smaller than that of the second sampling point, and a distance deviation value of each sampling point on the first sub-curve segment increases with an increase in the sampling voltage, the second sub-curve segment is a curve segment on the first curve segment whose sampling voltage is larger than that of the second sampling point, and a distance deviation value of each sampling point on the second sub-curve segment decreases with an increase in the sampling voltage.

With reference to the sixth aspect, in a second possible implementation, the management system receives a plurality of sets of sampling data of a first set of N sampling time periods that are serially connected at a plurality of sampling voltages, and determines an operating characteristic curve of each sampling time period based on the plurality of sets of sampling data of each sampling time period, where the N sampling time periods include a first time period, the N sampling time periods are different from each other, the operating characteristic curve of each sampling time period includes a first curve segment of each sampling time period, and the first curve segment of each sampling time period is an operating characteristic curve obtained by sampling in a first sampling voltage interval. And determining whether the first group of strings has a fault according to the distance deviation value from each sampling point on the first curve segment of each sampling time period to the first straight line corresponding to the first curve segment of each sampling time period, wherein the first straight line corresponding to the first curve segment of each sampling time period is determined by the initial sampling point and the final sampling point of the first curve segment of each sampling time period.

With reference to the sixth aspect, in a third possible implementation, the N sampling time periods include a second sampling time period, and an interval duration between the second sampling time period and the first sampling time period is greater than a preset interval duration threshold.

With reference to the sixth aspect, in a fourth possible implementation, the N sampling periods include N-1 third sampling periods. The management system receives a plurality of groups of sampling data of a first sampling time period of a first group of strings under a plurality of sampling voltages, and determines a working characteristic curve of the first sampling time period based on the plurality of groups of sampling data of the first sampling time period, wherein the working characteristic curve of the first sampling time period comprises a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a first sampling voltage interval. And further determining an initial working state of the first group of strings according to the distance deviation amount from each sampling point on the first sampling time period to a first straight line corresponding to a first curve segment of the first sampling time period, and receiving multiple groups of sampling data of the first group of strings in N-1 third sampling time periods when the initial working state is the first working state.

In a seventh aspect, the present application provides a method for identifying a fault in a string set, which is applicable to a power supply system including a sampling device, an inverter, and a first string set connected to the inverter. The management system receives a plurality of groups of sampling data of a first group of sampling time periods which are serially connected under a plurality of sampling voltages and sent by a sampling device, and determines a working characteristic curve of the first sampling time period based on the plurality of groups of sampling data of the first sampling time period, wherein the working characteristic curve of the first sampling time period comprises a plurality of curve segments of the first sampling time period, and each curve segment of the first sampling time period is a working characteristic curve obtained by sampling in each sampling voltage interval. And determining the first derivative characteristic value of each curve segment of the first sampling time period, and determining whether the working characteristic curve of the first group of strings in the first sampling time period is distorted according to the first derivative characteristic value of each curve segment of the first sampling time period, thereby determining whether the first group of strings is in failure.

With reference to the seventh aspect, in a first possible implementation manner, the plurality of curve segments include a first curve segment, a second curve segment and a third curve segment, where the first curve segment is an operating characteristic curve sampled in a first sampling voltage interval, the second curve segment is an operating characteristic curve sampled in a second sampling voltage interval, the third curve segment is an operating characteristic curve sampled in a third sampling voltage interval, the second sampling voltage interval is adjacent to the first sampling voltage interval and the third sampling voltage interval, and a sampling voltage of each sampling point in the second sampling voltage interval is greater than a sampling voltage of each sampling point in the first sampling voltage interval and is smaller than a sampling voltage of each sampling point in the third sampling voltage interval. The management system determines whether the first set of strings is faulty based on a sixth difference between the first derivative characteristic value of the first curve segment and the first derivative characteristic value of the second curve segment, and a seventh difference between the first derivative characteristic value of the second curve segment and the first derivative characteristic value of the third curve segment.

With reference to the seventh aspect, in a second possible implementation manner, the management system determines that the first group of strings has a fault when a ratio between the sixth difference and the seventh difference is greater than a preset ratio threshold.

With reference to the seventh aspect, in a third possible implementation manner, the management system determines that the first group of strings has a fault when the sixth difference is greater than a seventh preset difference threshold and the seventh difference is less than an eighth preset difference threshold.

With reference to the seventh aspect, in a fourth possible implementation, the management system determines a first derivative value of each sampling point on each curve segment, and determines an average of the first derivative values of all the sampling points on each curve segment as a first derivative characteristic value of each curve segment.

With reference to the seventh aspect, in a fifth possible implementation manner, the management system receives a first group of sets of sampling data of N sampling time periods that are serially connected under multiple sampling voltages, and determines an operating characteristic curve of each sampling time period based on the sets of sampling data of each sampling time period, where the N sampling time periods include the first time period, the N sampling time periods are different from each other, the operating characteristic curve of each sampling time period includes multiple curve segments of each sampling time period, and each curve segment of each sampling time period is an operating characteristic curve obtained by sampling in each sampling voltage interval. And further determining the first derivative characteristic value of each curve segment of each sampling time period, and determining whether the first group of strings have faults or not according to the first derivative characteristic value of each curve segment of each sampling time period.

With reference to the seventh aspect, in a sixth possible implementation, the N sampling time periods include a second sampling time period, and an interval duration between the second sampling time period and the first sampling time period is greater than a preset interval duration threshold.

With reference to the seventh aspect, in a seventh possible implementation, the N sampling periods include N-1 third sampling periods. The management system receives a plurality of groups of sampling data of a first sampling time period of a first group of strings under a plurality of sampling voltages, and determines a working characteristic curve of the first sampling time period based on the plurality of groups of sampling data of the first sampling time period, wherein the working characteristic curve of the first sampling time period comprises a plurality of curve segments of the first sampling time period. And determining an initial working state of the first group of strings according to the first derivative characteristic values of all curve segments of the first sampling time period, and receiving a plurality of groups of sampling data of the first group of strings in the N-1 third sampling time periods when the initial working state is the first working state.

In an eighth aspect, the present application provides a method for identifying a fault in a string set, the method being applied to a power supply system including a sampling device, an inverter, and a first string set connected to the inverter. The management system receives a plurality of groups of sampling data of a first sampling time period of a first group of sampling voltages in series sent by the sampling device, determines a working characteristic curve of the first sampling time period based on the plurality of groups of sampling data of the first sampling time period, and each sampling point on the working characteristic curve of the first sampling time period corresponds to each sampling voltage one by one. And then, determining whether the working characteristic curve of the first group of strings in the first sampling time period is distorted according to the second derivative value of the third sampling point on the working characteristic curve of the first sampling time period, and further determining whether the first group of strings is in failure.

With reference to the eighth aspect, in a first possible implementation manner, when the second derivative value of the third sampling point is 0, the management system determines that the point is a distortion point on the working characteristic curve of the first group of strings in the first sampling time period, and further determines that the first group of strings has a fault.

With reference to the eighth aspect, in a second possible implementation manner, the management system receives a plurality of sets of sampling data of a first set of sampling time periods that are serially connected to the plurality of sampling voltages, and determines an operating characteristic curve of each sampling time period based on the plurality of sets of sampling data of each sampling time period, where the N sampling time periods include the first time period, the N sampling time periods are different from each other, and each sampling point on the operating characteristic curve of each sampling time period corresponds to each sampling voltage one to one. And then determining whether the first group of strings are in failure according to the second derivative value of the third sampling point on the working characteristic curve of each sampling time period.

With reference to the eighth aspect, in a third possible implementation, the N sampling time periods include a second sampling time period, and an interval duration between the second sampling time period and the first sampling time period is greater than a preset interval duration threshold.

With reference to the eighth aspect, in a fourth possible implementation, the N sampling periods include N-1 third sampling periods. The management system receives a plurality of groups of sampling data of a first sampling time period of a first group of strings under a plurality of sampling voltages, and determines a working characteristic curve of the first sampling time period based on the plurality of groups of sampling data of the first sampling time period. And then determining the initial working state of the first group of strings according to the second derivative value of the third sampling point on the working characteristic curve of the first sampling time period, and receiving multiple groups of sampling data of the first group of strings in N-1 third sampling time periods when the initial working state is the first working state.

It should be understood that the implementations and advantages of the various aspects described above in this application are mutually referenced.

Drawings

Fig. 1 is a schematic view of an application scenario of a power supply system provided in the present application;

FIG. 2 is a schematic diagram of the power supply system provided herein;

FIG. 3 is a schematic illustration of a first curve segment and a second curve segment on an IV curve as provided herein;

FIG. 4 is a schematic diagram illustrating the distance deviation values from the first straight line of each sample point on the first curve segment of the normal string provided by the present application;

FIG. 5 is a schematic diagram illustrating the distance deviation values from the first straight line of each sampling point on the first curve segment of the fault group string provided by the present application;

FIG. 6 is a flow chart of a method for identifying a fault in a string provided herein;

FIG. 7 is another schematic flow chart diagram of a method for identifying faults in a group string provided herein;

FIG. 8 is another schematic flow chart diagram of a method for identifying faults in a group string provided herein;

fig. 9 is a schematic flow chart of a fault identification method for a group string provided in the present application.

Detailed Description

A large amount of statistical data of the power supply system show that quality problems at the initial stage of the string and faults generated at the final stage are important factors influencing the power generation amount of the power supply system. The fault detection of the string can be fed back through parameters such as string current/voltage/power. Typical identification means for the present comparison include thermal infrared imaging, detection of electroluminescence characteristics of the components, and analysis processing based on a string current-voltage curve (hereinafter referred to as "IV curve"). Typically, for preliminary identification of string faults, the IV curve of the string may be used, for example, based on the collected string IV data, determining whether the string is disconnected by string current, determining whether there is a failure or a component voltage fault in the string by string voltage, etc. For the group string hidden and non-human eye visible faults, identification is often required through a typical physical or mathematical model, characteristic parameters of the group string are simulated based on typical model calculation, and fault identification of the group string is realized based on the characteristic parameters of the group string. The fault identification mode based on the model has large dependence on component technology, and has poor applicability in different application scenes.

The application provides a power supply system can confirm whether this work characteristic curve takes place the distortion according to the analysis of the work characteristic curve of group cluster, and then realizes the fault identification to this group cluster, need not rely on the subassembly technique, and the suitability is strong. The power supply system provided by the application can be adapted to different application scenes, such as a photovoltaic power supply scene, a light and storage hybrid power supply scene, an energy storage power supply scene and the like. In a photovoltaic power supply scene, the first group of strings are photovoltaic group strings; in a light storage hybrid power supply scene, a first group of strings are photovoltaic group strings or energy storage battery group strings; in the energy storage and power supply scene, the first group string is an energy storage battery group string. The following description takes a photovoltaic power supply scenario as an example.

Referring to fig. 1, fig. 1 is a schematic view of an application scenario of a power supply system provided in the present application. As shown in fig. 1, a power supply system may include a photovoltaic power supply device and an inverter connected to the photovoltaic power supply device, wherein the photovoltaic power supply device may include a first group of strings and a photovoltaic adapter connected to the first group of strings. The first string is a photovoltaic string, and each photovoltaic string may include a plurality of photovoltaic modules connected in series and/or in parallel. It can be understood that the photovoltaic adapter may adjust its output voltage and/or output current based on the voltage and/or current requirement corresponding to the photovoltaic string connected to it, and output the output voltage and/or output current to the inverter, and the inverter inverts the voltage and/or current output by the photovoltaic adapter into alternating current, thereby realizing power supply to various types of electric devices such as an alternating current grid or an alternating current load (e.g., a household electrical appliance). In an optional implementation scenario, the power supply system may also be applied to a scenario of an uninterruptible power supply, that is, the power supply system may be provided with an energy storage battery, such as a nickel-cadmium battery, a nickel-hydrogen battery, a lithium ion battery, a lithium polymer battery, and the like.

In some possible embodiments, the power supply system may obtain, based on a manner in which the management system sends a string operating parameter obtaining instruction to the inverter, multiple sets of sampling data within a preset scanning sampling voltage interval obtained by scanning the photovoltaic string connected to the inverter in a first sampling time period, that is, multiple sets of sampling data (e.g., current and voltage values of the photovoltaic string) in the first sampling time period. Then, a working characteristic curve (such as an IV curve) of the photovoltaic group string is determined according to a plurality of groups of sampling data of a first sampling time period of the photovoltaic group string, and a curvature value/a second derivative value of a first sampling point on the working characteristic curve, a curvature characteristic value of the first curve segment, curvature characteristic values of two/three adjacent curve segments, a distance deviation value from a first straight line corresponding to the first curve segment to each sampling point on the first curve segment, and any one value of a first derivative characteristic value of each curve segment are determined, and whether the working characteristic curve of the photovoltaic group string is distorted is determined according to any one value, so that whether the photovoltaic group string is in fault is determined, assembly technology is not needed, and applicability is high.

It should be noted that the management system and the sampling device in the present application may be integrated into the inverter, may be integrated into other devices, or may exist independently. The following describes the power supply system and its operation principle provided in the present application with reference to fig. 2 to 5, taking the example that the sampling device is integrated in the inverter and the management system exists independently.

Referring to fig. 2, fig. 2 is a schematic structural diagram of a power supply system provided in the present application. As shown in fig. 2, the power supply system 10 includes the group strings 111, …, the group string 11a, the group strings 11m, …, the group string 11z, the inverters 121, …, the inverter 12n, and the management system 13. The string groups 111, … and 11a are all connected with the input end of the inverter 121, …, the string groups 11m, … and 11z are all connected with the input end of the inverter 12n, and the output end of the inverter 121, the output end of … and the output end of the inverter 12n are connected in parallel to a grid-connected point. The inverter 121 includes a sampling device 1211, configured to collect sampling data of the string sets 111 and … and the string set 11 a; …, respectively; the inverter 12n includes a sampling device 12n1 for collecting sampled data of the string sets 11m, …, and the string set 11 z. All strings connected to the inverters 121 and … and the inverter 12n may be photovoltaic strings, energy storage battery strings, photovoltaic strings in one part, and energy storage battery strings in another part. The management system 13 may communicate with each inverter through a wireless communication unit (e.g., WiFi, Lora, Zigbee, etc.) or a PLC communication unit. The inverter is used for carrying out IV curve scanning on the group strings connected with the inverter so as to detect whether the group strings connected with the inverter have defects or damages. The inverter can also be used for converting the direct current output by the string into alternating current and outputting the alternating current to an alternating current power grid.

In one possible embodiment, after the power supply system 10 starts operating, the management system 13 sends a group string scan command to each inverter. Each inverter acquires a plurality of working parameters (such as output current or output power of the group string) of each group string connected with the inverter under a plurality of sampling voltages within a first sampling time period and a preset scanning sampling voltage interval through a respective sampling device according to a received group string scanning instruction, thereby acquiring a plurality of groups of sampling data of each group string in the first sampling time period and the first sampling time period within the preset scanning sampling voltage interval, and returning the plurality of groups of sampling data of each group string under the first sampling time periods of a plurality of sampling voltages to the management system 13. Each set of sampling data includes an output current value/output power value of the set string and an output voltage value, and the following description is made with each set of sampling data including an output current value and an output voltage value of the set string.

Since the management system 13 in the power supply system 10 recognizes a fault for each group string in the same manner, the group string 111 will be described as an example.

Specifically, when receiving the group string scanning instruction, the inverter 121 starts to ensure that the inverter 121 is turned off by controlling its own switching tube, so that the group string 111 is open-circuited, that is, the output voltage of the group string 111 is an open circuit, and according to a preset dropping rule, the output voltage of the group string 111 is dropped to 0 from the open circuit voltage by adjusting the on-off duration of its own switching tube, and the sampling device 1211 is used to collect the scanning data of the group string 111 in a first sampling time period (that is, the time when the inverter 121 starts scanning the group string 111 — the time when the inverter 121 finishes scanning the group string 111) and a preset scanning sampling voltage period (that is, 0 — the open circuit voltage of the group string 111), so as to obtain multiple sets of current-voltage values of the group string 111 in the first sampling time periods under multiple sampling voltages in the preset scanning sampling voltage period.

The preset decreasing rule can be at least one of a voltage decreasing rule of a fixed pressure difference, a voltage decreasing rule of a parabola or a voltage decreasing rule of a fixed duty ratio change rate. The parabolic voltage drop rule may mean that the output voltage near the first string drops faster near an open-circuit voltage, and drops slower near the first string when the output voltage is 0; the parabolic voltage drop law may also mean that the output voltage near the first string drops more slowly near an open circuit voltage and drops more quickly near 0. The voltage droop law for a fixed duty cycle rate may refer to the control duty cycle of the inverter changing in fixed steps from an initial condition, such as the inverter control duty cycle starting at 0 and increasing to 1 in fixed steps of 0.01.

Then, the management system 13 fits to obtain an IV curve of the group string 111 in the first sampling time period, that is, an IV curve of the first sampling time period, according to the received multiple groups of current and voltage values of the group string 111 in the first sampling time period under different sampling voltages, where each sampling point on the IV curve of the first sampling time period corresponds to each sampling voltage one to one.

In a possible embodiment, after obtaining the IV curve of the first sampling time period, the management system 13 calculates a first derivative function formula I ═ f' (U) and a second derivative function formula I ═ f ″ (U) of the IV curve of the first sampling time period according to the function formula I ═ f (U) of the IV curve of the first sampling time period. Then, the management system 13 calculates a first derivative value and a second derivative value of the first sampling point on the IV curve of the first sampling period according to I ═ f' (U) and I ═ f ″ (U), and further calculates a curvature value of the first sampling point

Wherein, f' (U)₁) And f' (U)₁) First and second derivative values of the IV curve at the first sampling point for the first sampling period, respectively. Here, the curvature value of each sampling point is a rotation rate of a tangential direction angle to an arc length for each sampling point on the IV curve, and is used to indicate a degree of curvature of the curve at a certain point.

In an optional embodiment, the management system 13 traverses the curvature value of each sampling point on the IV curve of the first sampling period, and when there is a sampling point (i.e., a first sampling point) on the IV curve of the first sampling period, where the curvature value is greater than the preset curvature threshold, it indicates that the first sampling point is a distortion point on the IV curve, and thus determines that the string 111 fails. It will be appreciated that since the trend of the curvature values of the IV curve of a normal string is relatively flat, it is possible to determine whether there is a fault in the string by the presence or absence of a distortion point on the IV curve.

In another optional embodiment, the management system 13 determines a curve segment corresponding to a first sampling voltage interval on an IV curve of a first sampling time period as a first curve segment of the first sampling time period, and obtains a standard curve segment corresponding to the first curve segment, where the standard curve segment is a working characteristic curve acquired by stringing the first sampling voltage interval in a normal group, sampling voltages of a plurality of standard sampling points on the standard curve segment are respectively corresponding to and the same as sampling voltages of a plurality of sampling points on the first curve segment, and the first curve segment includes the first sampling point. And calculating the curvature value of each sampling point on the first curve segment according to the manner of calculating the curvature value of the first sampling point, and determining the similarity between the first curve segment and the standard curve segment according to the curvature value of each sampling point on the first curve segment and the standard curvature value of each standard sampling point on the standard curve segment. And when the similarity is smaller than a preset similarity threshold, the first curve segment is distorted, and the fault of the group string 111 is determined.

Illustratively, assume a sample point x on the first curve segment₁,x₂,…,x_nRespectively has a curvature value of K₁₁,K₁₂,…,K_1nSampling point y on the standard curve segment₁,y₂,…,y_nRespectively has a curvature value of K₂₁,K₂₂,…,K_2n. The management system 13 calculates the similarity between the first curve segment and the standard curve segment according to a formula

Wherein, Cov (K)₁,K₂) Is K₁,K₂The covariance of (a) of (b),D(K₁)、D9K₂) Are each K₁、K₂The variance of (c).

In another optional embodiment, the management system 13 determines a curve segment corresponding to a first sampling voltage interval on the IV curve of the first sampling time period as a first curve segment of the first sampling time period, and determines a curve segment corresponding to a second sampling voltage interval on the IV curve of the first sampling time period as a second curve segment of the first sampling time period. The first sampling voltage interval is adjacent to the second sampling voltage interval, the sampling voltage of each sampling point in the first sampling voltage interval is larger than that of each sampling point in the second sampling voltage interval, and the first curve segment comprises the first sampling point. The first sampling voltage interval and the second sampling voltage interval are both located in a preset scanning sampling voltage interval. The interval length corresponding to the first sampling voltage interval may be the same as or different from the interval length corresponding to the second sampling voltage interval, which is not limited in the present application.

Illustratively, referring to fig. 3, fig. 3 is a schematic illustration of a first curve segment and a second curve segment on an IV curve as provided herein. As shown in FIG. 3, the first curve segment is a first sampling voltage interval [2V ] on the IV curve_o/7,9V_o/14]Corresponding to the curve part, the second curve segment is the second sampling voltage interval (9V) on the IV curve_o/14,13V_o/14]The corresponding curved portion.

Then, the management system 13 calculates the curvature values of the sampling points on the first curve segment and the second curve segment according to the above manner of calculating the curvature values of the first sampling points, determines the average value of the curvature values of all the sampling points on the first curve segment as the first curvature characteristic value of the first curve segment, determines the average value of the curvature values of all the sampling points on the second curve segment as the second curvature characteristic value of the second curve segment, and calculates the difference between the first curvature characteristic value and the second curvature characteristic value to obtain the first difference. When the first difference is greater than a first preset difference threshold, it is indicated that the variation trend (i.e., decreasing) of the curvature characteristic values of the first curve segment and the second curve segment is greatly deviated from the variation trend (i.e., increasing) of the curvature characteristic values of two adjacent curve segments of the normal string, and it is determined that the IV curve of the string 111 is distorted, so that the failure of the string 111 is determined.

It will be appreciated that for a normal string of sets, n adjacent curve segments S are obtained by dividing the IV curve of the string of sets₁,S₂,…,S_nIn, S₁Characteristic value of curvature of<S₂Characteristic value of curvature of<…<S_nA characteristic value of curvature of (1), wherein S₁At S₂Before, …, S_n-1At S_nBefore. In other words, for normal string, S₁,S₂,…，S_nMonotonically increases in the curvature feature value of (c). Thus, a string fault may be determined when two adjacent curve segments exist on the IV curve of the string and the curvature characteristic value of the previous curve segment is greater than the curvature characteristic value of the subsequent curve segment.

In another optional embodiment, the management system 13 may determine a curve segment corresponding to a first sampling voltage interval on the IV curve of the first sampling time period as a first curve segment of the first sampling time period, determine a curve segment corresponding to a second sampling voltage interval on the IV curve of the first sampling time period as a second curve segment of the first sampling time period, and determine a curve segment corresponding to a third sampling voltage interval on the IV curve of the first sampling time period as a third curve segment of the first sampling time period. The first curve segment is a working characteristic curve obtained by sampling in a first sampling voltage interval, the second curve segment is a working characteristic curve obtained by sampling in a second sampling voltage interval, the third curve segment is a working characteristic curve obtained by sampling in a third sampling voltage interval, the second sampling voltage interval is adjacent to the first sampling voltage interval and the third sampling voltage interval respectively, the sampling voltage of each sampling point in the second sampling voltage interval is greater than the sampling voltage of each sampling point in the first sampling voltage interval, and is less than the sampling voltage of each sampling point in the third sampling voltage interval, and the first curve segment comprises a first sampling point. The first sampling voltage interval, the second sampling voltage interval and the third sampling voltage interval are all located in a preset scanning sampling voltage interval. The interval length corresponding to the first sampling voltage interval, the interval length corresponding to the second sampling voltage interval and the interval length corresponding to the third sampling voltage interval may be the same or different from each other, and the application does not limit this.

Then, the management system 13 calculates the curvature value of each sampling point on the first curve segment, the curvature value of each sampling point on the second curve segment, and the curvature value of each sampling point on the third curve segment according to the above-mentioned manner of calculating the curvature value of the first sampling point. And determining an average of the curvature values of all points on the first curve segment as a first curvature characteristic value of the first curve segment, determining an average of the curvature values of all points on the second curve segment as a second curvature characteristic value of the second curve segment, and determining an average of the curvature values of all points on the third curve segment as a third curvature characteristic value of the third curve segment. And further calculating a difference value between the first curvature characteristic value and the second curvature characteristic value to obtain a first difference value, and calculating a difference value between the second curvature characteristic value and the third curvature characteristic value to obtain a second difference value. When the first difference is smaller than the second preset difference threshold and the second difference is larger than the third preset difference threshold, it is indicated that the variation trend (i.e., increasing first and then decreasing) of the curvature characteristic values of the first curve segment, the second curve segment and the third curve segment is greatly deviated from the variation trend (i.e., increasing all the time) of the curvature characteristic values of the three adjacent curve segments of the normal string group, and it is determined that the string group 111 has a fault.

It will be appreciated that for a normal string of sets, n adjacent curve segments S are obtained by dividing the IV curve of the string of sets₁,S₂,…,S_nIn, S₁Characteristic value of curvature of<S₂Characteristic value of curvature of<…<S_nA characteristic value of curvature of (1), wherein S₁At S₂Before, …, S_n-1At S_nBefore. In other words, for normal string, S₁,S₂,…,S_nMonotonically increases in the curvature feature value of (c). Thus, when three adjacent curve segments exist on the IV curve of the group string, and the curvature characteristic value of the previous curve segment and the curvature characteristic value of the next curve segment in the three adjacent curve segments are both smaller than the curvature characteristic value of the middle curve segment, it is ensured thatThe set of strings is determined to be faulty.

In the present application, the power supply system 10 may determine whether the IV curve of the string group is distorted based on the curvature value of the first sampling point on the IV curve of the string group, the curvature value of each sampling point on the first curve segment, the curvature characteristic values of two adjacent curve segments, or the curvature characteristic values of three adjacent curve segments by the management system 13, and then determine whether the string group is faulty, and it is not necessary to rely on the component technology, and it is also applicable to the string group produced by any manufacturer, and the applicability is strong.

It should be noted that, after determining that the string 111 has a fault according to the above-mentioned manner, in order to avoid fault misidentification caused by blocking the string due to factors such as environment, the management system 13 may further obtain, through the inverter 121, a first set of operating current data of the string 111 in a first operating time period corresponding to the inverter 121 from power on to power off, and obtain that the normal string is not blocked, in a second working time period corresponding to the time from starting to shutting down of the inverter connected with the inverter, the second group of working current data of the normal group string, wherein, each first working current value in the first group of working current data corresponds to each first sampling time in the first working time period one by one, each second working current value in the second group of working current data corresponds to each second sampling time in the second working time period one by one, and the first sampling time corresponding to each first working current value is the same as the second sampling time corresponding to each second working current value. The first working time period is located before the first sampling time period, and the interval duration between the first working time period and the first sampling time period is not limited in the application.

Then, the management system 13 calculates the similarity between the first group of working current data and the second group of working current data, and when the similarity is smaller than a preset similarity threshold, it indicates that the group string 111 is blocked in the first sampling time period, and then corrects the fault identification result of the group string 111 in the first sampling time period to that the group string 111 has no fault; when the similarity is greater than or equal to the preset similarity threshold, it is indicated that the group string 111 is not shielded in the first sampling time period, and there is no fault misidentification condition caused by the shielded group string, and a fault identification result of the group string 111 at the first sampling time, that is, a fault of the group string 111, is reported to a worker and an alarm is given. It can be understood that the situation of fault misidentification caused by shielding the group string can be effectively avoided through the mode, the accuracy of group string fault identification can be further improved, and the applicability is strong.

Further, the power supply system 10 provided by the present application may also determine whether a string has a fault based on the management system 13 according to the working characteristic curves of a plurality of sampling time periods, in a specific manner as follows:

in an optional embodiment, the management system 13 sends the group string scanning command to the inverter 121N times at preset time intervals, where N is an integer greater than or equal to 2, and the time intervals of two adjacent group string scanning commands sent by the management system 13 to the inverter 121 may be the same or different, which is not limited in this application. The inverter 121 acquires a plurality of working parameters of the group string 111 under a plurality of sampling voltages in N sampling time periods and a preset scanning sampling voltage interval according to the received N times of group string scanning instructions, thereby acquiring a plurality of groups of sampling data of the group string 111 under N sampling time periods and N sampling time periods in the preset scanning sampling voltage interval, and returning the plurality of groups of sampling data of the group string 111 under N sampling time periods under a plurality of sampling voltages to the management system 13, wherein the N sampling time periods include a first sampling time period and the N sampling time periods are different from each other, and each sampling point on a working characteristic curve of each sampling time period corresponds to each sampling voltage one to one.

The management system 13 fits to obtain an IV curve of each sampling period of the group string 111 in N sampling periods according to the received multiple groups of current and voltage values of the group string 111 in N sampling periods under different sampling voltages.

In an optional embodiment, the management system 13 determines whether a first sampling point having a curvature value greater than a preset curvature threshold exists on an IV curve of each sampling time period, counts the number of IV curves having the first sampling point on the IV curve in N IV curves of N sampling time periods, and determines that the string 111 fails when the number of the IV curves is greater than the preset number threshold.

In another optional embodiment, each of the N IV curves of the N sampling time periods includes a first curve segment, where the first curve segment of each sampling time period is an operating characteristic curve obtained by sampling in each sampling time period and the first sampling voltage interval, and the first curve segment of each sampling time period includes the first sampling point.

The management system 13 obtains the standard curve segment corresponding to the first curve segment of each sampling time period, and determines the similarity between the first curve segment of each sampling time period and the standard curve segment according to the curvature value of each sampling point on the first curve segment of each sampling time period and the standard curvature value of each standard sampling point on the standard curve segment corresponding to the first curve segment of each sampling time period. And counting the number of the first curve segments with the similarity smaller than a preset similarity threshold value in the N first curve segments in the N sampling time periods, and determining that the group string 111 fails when the number of the first curve segments is larger than the preset number threshold value.

In another optional embodiment, each of the N IV curves of the N sampling time periods includes a first curve segment and a second curve segment, where the first curve segment of each sampling time period is an operating characteristic curve sampled in each sampling time period and a first sampling voltage interval, and the second curve segment of each sampling time period is an operating characteristic curve sampled in each sampling time period and a second sampling voltage interval, where the first sampling voltage interval is adjacent to the second sampling voltage interval, and the sampling voltage of each sampling point in the first sampling voltage interval is greater than the sampling voltage of each sampling point in the second sampling voltage interval. The first curve segment of each sampling time segment comprises a first sampling point.

The management system 13 determines a first curvature characteristic value of the first curve segment of each sampling time period according to the curvature value of each sampling point on the first curve segment of each sampling time period, and determines a second curvature characteristic value of the second curve segment of each sampling time period according to the curvature value of each sampling point on the second curve segment of each sampling time period. And calculating a first difference value between the first curvature characteristic value and the second curvature characteristic value of each sampling time period, and counting the number of IV curves of which the first difference value is greater than a first preset difference value threshold value in N IV curves of the N sampling time periods. And when the number of the IV curves is larger than a preset number threshold value, determining that the string 111 has a fault.

In yet another alternative embodiment, each of the N IV curves for the N sampling time periods includes a first curve segment, a second curve segment, and a third curve segment, wherein, the first curve section of each sampling time period is a working characteristic curve obtained by sampling in each sampling time period and the first sampling voltage interval, the second curve section of each sampling time period is a working characteristic curve obtained by sampling in each sampling time period and the second sampling voltage interval, the third curve section of each sampling time period is a working characteristic curve obtained by sampling in each sampling time period and the third sampling voltage interval, the second sampling voltage interval is adjacent to the first sampling voltage interval and the third sampling voltage interval respectively, and the sampling voltage of each sampling point in the second sampling voltage interval is greater than the sampling voltage of each sampling point in the first sampling voltage interval and is smaller than the sampling voltage of each sampling point in the third sampling voltage interval. The first curve segment of each sampling time segment comprises a first sampling point.

The management system 13 determines a first curvature characteristic value of the first curve segment of each sampling time period according to the curvature value of each sampling point on the first curve segment of each sampling time period, determines a second curvature characteristic value of the second curve segment of each sampling time period according to the curvature value of each sampling point on the second curve segment of each sampling time period, and determines a third curvature characteristic value of the third curve segment of each sampling time period according to the curvature value of each sampling point on the third curve segment of each sampling time period. And calculating a first difference value between the first curvature characteristic value and the second curvature characteristic value of each sampling time period and a second difference value between the second curvature characteristic value and the third curvature characteristic value, and counting the number of IV curves of which the first difference value is smaller than a second preset difference threshold value and the second difference value is larger than a third preset difference threshold value in N IV curves of the N sampling time periods. And when the number of the IV curves is larger than a preset number threshold value, determining that the string 111 has a fault.

Here, the specific implementation processes of the management system 13 determining the curvature value of each sampling point on the IV curve of each time period, the similarity between the first curve segment and the corresponding standard curve segment, the curvature characteristic value of each curve segment, and the like may refer to the specific implementation manner in which the management system 13 determines whether the group string 111 fails according to the IV curve of the first sampling time period in the above embodiment, and details are not described here.

It can be understood that whether the group string is in failure is determined through a plurality of working characteristic curves of the group string in a plurality of different sampling time periods, the influences of environmental factors (such as cloud shielding, shielding in different degrees between the group string due to different solar altitude angles in the morning and evening) and fluctuation of test equipment due to single failure recognition can be effectively avoided, the condition of group string failure misrecognition is caused, the accuracy of group string failure detection is improved, and the applicability is stronger.

It should be noted that, in order to further avoid the influence of fluctuation due to long-time environmental factors (e.g., cloud throughout the day) on string fault identification and improve the accuracy of string fault detection, the N sampling time periods may include a second sampling time period, where the second sampling time period is later than the first sampling time period, and an interval duration between the second sampling time period and the first sampling time period (i.e., an interval duration between a maximum sampling time in the first sampling time period and a minimum sampling time in the second sampling time period) is greater than a preset interval duration threshold. Illustratively, the preset interval duration threshold is greater than or equal to 12 hours.

In another embodiment, the management system 13 receives multiple sets of sampling data of the inverter 121 in the first sampling time period and the preset scan sampling voltage interval, and fits to obtain an IV curve of the group string 111 in the first sampling time period, that is, an IV curve of the first sampling time period, according to the multiple sets of sampling data of the first sampling time period. The management system 13 may be configured to determine that the curvature value of the first sampling point on the IV curve of the first sampling time period is greater than the preset curvature threshold, or that the similarity between the first curve segment on the IV curve of the first sampling time period and the standard curve segment corresponding to the first curve segment is less than the preset similarity threshold, or that the first difference between the first curvature feature value of the first curve segment on the IV curve of the first sampling time period and the second curvature feature value of the second curve segment on the IV curve of the first sampling time period is greater than the first preset difference threshold, or that the first difference between the first curvature feature value of the first curve segment on the IV curve of the first sampling time period and the second curvature feature value of the second curve segment on the IV curve of the first sampling time period is less than the second preset difference threshold, and that the second curvature feature value of the second curve segment on the IV curve of the first sampling time period and the third curve segment on the IV curve of the first sampling time period are less than the second preset difference threshold The initial operating state of the string set 111 is determined to be a fault state, i.e., the first operating state, in such a manner that the second difference between the three curvature characteristic values is greater than the third preset difference threshold value.

Then, when determining that the initial operating state of the group string 111 is the fault state, the management system 13 sends the group string scanning instruction to the inverter 121N-1 times according to a preset time interval, where N is an integer greater than or equal to 2, and the time intervals of two adjacent group string scanning instructions sent by the management system 13 to the inverter 121 may be the same or different, which is not limited in this application. The inverter 121 acquires a plurality of working parameters of the string 111 under a plurality of sampling voltages within N-1 sampling time periods and a preset scanning sampling voltage interval according to the received N-1 times of string scanning instructions, thereby acquiring a plurality of groups of sampling data of the string 111 under N-1 sampling time periods and N-1 sampling time periods within the preset scanning sampling voltage interval, and returning the plurality of groups of sampling data of the string 111 under the plurality of sampling voltage periods to the management system 13.

The management system 13 fits to obtain an IV curve of each sampling period of the group string 111 in N-1 sampling periods according to the received multiple groups of current-voltage values of the group string 111 in N-1 sampling periods under different sampling voltages. The management system 13 determines the number of IV curves, in the N-1 IV curves in the N-1 sampling time periods, that satisfies that the curvature value of the first sampling point is greater than the preset curvature threshold, or the similarity between the first curve segment of each sampling time period and the standard curve segment corresponding to the first curve segment is less than the preset similarity threshold, or the first difference between the first curvature characteristic value of the first curve segment of each sampling time period and the second curvature characteristic value of the second curve segment is greater than the first preset difference threshold, or the first difference between the first curvature characteristic value of the first curve segment of each sampling time period and the second curvature characteristic value of the second curve segment is less than the second preset difference threshold and the second difference between the second curvature characteristic value of the second curve segment and the third curvature characteristic value of the third curve segment is greater than the third preset difference threshold, when the number of IV curves is greater than the preset number threshold, it is determined that group string 111 is faulty.

It can be understood that, in the embodiment of the present application, in a case where the initial operating state of the group string is a fault state, the power supply system 10 may obtain, based on the management system 13, multiple sets of sampling data of the group string in multiple sampling time periods through the inverter connected to the group string, and as for a manner of directly obtaining multiple sets of sampling data of the group string in multiple sampling time periods, power generation loss of the inverter connected to the group string may be reduced, and thus power generation loss of the power supply system 10 may be reduced. In addition, the management system 13 determines whether the string group is faulty according to the working characteristic curves of a plurality of sampling time periods, so that the accuracy of detecting the string group fault can be improved, and the applicability is stronger.

In another possible embodiment, after obtaining the IV curve of the group string 111 in the first sampling time period (i.e., the IV curve of the first sampling time period), the management system 13 determines a curve segment corresponding to the first sampling voltage interval on the IV curve of the first sampling time period as a first curve segment, and calculates a first straight line l of the first curve segment according to the current-voltage value corresponding to the start sampling point and the current-voltage value corresponding to the end sampling point on the first curve segment₁Has a linear equation of A₁U+B₁I+C ₁0. Then, according to the formula

Calculating each sample point (U) on the first curve segment_i,I_i) To l₁Distance d of_1iI.e. each sample point to l₁Is calculated from the distance deviation value.

For ease of understanding, please refer to fig. 4, fig. 4 is a schematic diagram of the distance deviation value from the first straight line of each sample point on the first curve segment of the normal string provided in the present application. As shown in fig. 4, firstThe curve segment is a first sampling voltage interval [7V ] on the IV curve_o/14,13V_o/14]Corresponding curve part, namely a curve section from A to B on the IV curve, the initial sampling point A of the first curve section is the sampling voltage of 7V on the IV curve_oThe point corresponding to/14 is that the ending sampling point B is that the sampling voltage on the IV curve is 13V _o14, the straight line of the start sampling point A and the end sampling point B on the first curve segment is a first straight line l of the first curve segment₁Sampling points a to l on the first curve segment₁A distance of d_a。

It can be understood that the distance deviation value of each sampling point on the first curve segment (i.e. shown in fig. 4) of the normal string shows a trend of increasing and then decreasing with the increase of the sampling voltage, that is, in the first sub-curve segment and the second curve segment obtained by taking the sampling point a as the dividing point of the first curve segment, the distance deviation value of each sampling point on the first sub-curve segment increases with the increase of the sampling voltage and reaches the maximum value of the distance deviation value at the sampling point a, and then the distance deviation value of each sampling point on the second sub-curve segment decreases with the increase of the sampling voltage. Thus, the management system 13 can determine whether the string is faulty by the presence of the sampling point a on the first curve segment. Specifically, when the second sample point (i.e., sample point a) is not present on the first curve segment, the string 111 is determined to be faulty.

For example, please refer to fig. 5, fig. 5 is a schematic diagram illustrating a distance deviation value from a first straight line of each sampling point on a first curve segment of a fault group string provided by the present application. As shown in fig. 5, as the sampling voltage increases, the distance deviation value of each sampling point on the first curve segment increases, decreases, and increases, and decreases, that is, there is no second sampling point on the first curve segment, which indicates that the IV curve of the group of strings is distorted, and determines that the group of strings fails.

In the application, the power supply system 10 may determine whether the IV curve of the string group is distorted based on the variation trend of the distance characteristic value of each sampling point on the first curve segment in the IV curve of the string group by the management system 13, and further determine whether the string group is faulty, and it is not necessary to rely on the component technology, that is, it is applicable to the string group produced by any manufacturer, and the applicability is strong.

in an optional embodiment, the management system 13 sends the group string scanning command to the inverter 121N times at preset time intervals, where N is an integer greater than or equal to 2, and the time intervals of two adjacent group string scanning commands sent by the management system 13 to the inverter 121 may be the same or different, which is not limited in this application. The inverter 121 acquires a plurality of working parameters of the group string 111 at a plurality of sampling voltages within N sampling time periods and a preset scanning sampling voltage interval according to the received N times of group string scanning instructions, thereby acquiring a plurality of groups of sampling data of the group string 111 at N sampling time periods within N sampling time periods and a preset scanning sampling voltage interval, and returning the plurality of groups of sampling data of the group string 111 at N sampling time periods under a plurality of sampling voltages to the management system 13, wherein the N sampling time periods include a first sampling time period and the N sampling time periods are different from each other, the working characteristic curve of each sampling time period includes a first curve segment of each sampling time period, and the first curve segment of each sampling time period is a working characteristic curve sampled at each sampling time period and the first sampling voltage interval.

Specifically, the management system 13 determines a distance deviation value from each sampling point on the first curve segment of each sampling time period to the first straight line corresponding to the first curve segment of each sampling time period, and determines whether a second sampling point exists on the first curve segment of each sampling time period according to the distance deviation value of each sampling point on the first curve segment of each sampling time period, so as to count the number of the first curve segments, in which no second sampling point exists, in the N first curve segments of the N sampling time periods. And when the number of the first curve segments is greater than a preset number threshold, determining that the group string 111 fails, wherein a first straight line corresponding to the first curve segment in each sampling time period is determined by the initial sampling point and the final sampling point of the first curve segment in each sampling time period.

In another embodiment, the management system 13 receives multiple sets of sampling data of the inverter 121 in the first sampling time period and the preset scanning sampling voltage interval, and fits to obtain an IV curve of the group string 111 in the first sampling time period, that is, an IV curve of the first sampling time period, according to the multiple sets of sampling data of the first sampling time period, where the IV curve of the first sampling time period includes a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is an IV curve in the first sampling time period and the first sampling voltage interval. The management system 13 may determine that the initial operating state of the string group 111 is a fault state, i.e., a first operating state, by way of the absence of the second sampling point on the first curve segment of the first sampling time period.

The management system 13 fits to obtain an IV curve of each sampling period of the group string 111 in N-1 sampling periods according to the received multiple groups of current-voltage values of the group string 111 in N-1 sampling periods under different sampling voltages. The management system 13 determines the number of IV curves for which no second sample point exists on the first curve segment among the N-1 IV curves for the N-1 sampling time segments. And when the number of the IV curves is larger than a preset number threshold value, determining that the string 111 has a fault.

Here, a specific implementation process of the management system 13 determining whether the second sampling point exists on the first curve segment of each sampling time period may refer to a specific implementation manner of the management system 13 determining whether the group string 111 fails according to the first curve segment of the first sampling time period in the foregoing embodiment, and details are not described here.

In another possible embodiment, after obtaining the IV curve of the string 111, the management system 13 divides the IV curve of the string 111 into a plurality of curve segments according to a plurality of sampling voltage intervals. And calculating to obtain a first derivative functional relation I ═ f' (U) of the IV curve of the group string 111 according to the functional relation I ═ f (U) of the IV curve of the group string 111. And then, calculating to obtain a first derivative value of each sampling point on each curve segment according to the I ═ f' (U), and determining the average value of the first derivative values of each sampling point on each curve segment as a first derivative characteristic value of each curve segment. And then determines whether the string 111 is faulty according to the first derivative characteristic value of each curve segment.

The plurality of curve segments comprise a first curve segment, a second curve segment and a third curve segment, wherein the first curve segment is a working characteristic curve obtained by sampling in a first sampling voltage interval, the second curve segment is a working characteristic curve obtained by sampling in a second sampling voltage interval, the third curve segment is a working characteristic curve obtained by sampling in a third sampling voltage interval, the second sampling voltage interval is adjacent to the first sampling voltage interval and the third sampling voltage interval respectively, the sampling voltage of each sampling point in the second sampling voltage interval is larger than the sampling voltage of each sampling point in the first sampling voltage interval, and is smaller than the sampling voltage of each sampling point in the third sampling voltage interval. The interval length corresponding to the first sampling voltage interval, the interval length corresponding to the second sampling voltage interval and the interval length corresponding to the third sampling voltage interval may be the same or different from each other, and the application does not limit this.

After calculating the first derivative eigenvalue of the first curve segment, the second first derivative eigenvalue of the second curve segment, and the third first derivative eigenvalue of the third curve segment, the management system 13 determines whether the string group 111 fails according to a sixth difference between the first derivative eigenvalue and the second first derivative eigenvalue, and a seventh difference between the second first derivative eigenvalue and the third first derivative eigenvalue.

In an alternative embodiment, the management system 13 calculates a ratio between the sixth difference and the seventh difference, and determines that the string 111 fails when the ratio is greater than a predetermined ratio threshold, indicating that a distortion has occurred in the first curve segment, the second curve segment, and the third curve segment.

Further, after determining that the string is faulty, the management system 13 may also determine the fault level of the string 111 according to the deviation (i.e. difference) between the ratio and the preset ratio threshold. Specifically, the larger the deviation, the more serious the failure degree of the string becomes.

In another optional embodiment, when the sixth difference is greater than the seventh preset difference threshold and the seventh difference is less than the eighth preset difference threshold, the management system 13 indicates that the variation trend of the first derivative characteristic values of the first curve segment, the second curve segment and the third curve segment (i.e., decreasing first and then increasing) is more deviated from the variation trend of the first derivative characteristic values of the three adjacent curve segments of the normal string (i.e., decreasing always), and determines that the string 111 fails.

In the present application, the power supply system 10 may determine whether the IV curve of the string group is distorted based on the variation trend of the first derivative characteristic values of three adjacent curve segments on the IV curve of the string group by the management system 13, and further determine whether the string group is faulty, and it is not necessary to rely on the component technology, i.e., it is applicable to the string group produced by any manufacturer, and the applicability is strong.

Specifically, the management system 13 determines a first derivative characteristic value of the first curve segment, a second first derivative characteristic value of the second curve segment, and a third first derivative characteristic value of the third curve segment in each sampling time period, and determines whether the string 111 fails according to a sixth difference between the first derivative characteristic value and the second first derivative characteristic value in each sampling time period, and a seventh difference between the second first derivative characteristic value and the third first derivative characteristic value.

In an optional embodiment, the management system 13 calculates a ratio between the sixth difference and the seventh difference corresponding to each sampling time period, and counts the number of sampling time periods in which the ratio is greater than a preset ratio threshold in the N sampling time periods. And when the number of the sampling time periods is larger than a preset number threshold value, determining that the group string 111 has a fault.

In another optional embodiment, the management system 13 counts the number of sampling time periods in which the sixth difference value is greater than the seventh preset difference threshold value and the seventh difference value is less than the eighth preset difference threshold value among the N sampling time periods. And when the number of the sampling time periods is larger than a preset number threshold value, determining that the group string 111 has a fault.

In another embodiment, the management system 13 receives multiple sets of sampling data of the inverter 121 in the first sampling time period and the preset scanning sampling voltage interval, and fits to obtain an IV curve of the group string 111 in the first sampling time period, that is, an IV curve of the first sampling time period, according to the multiple sets of sampling data of the first sampling time period, where the IV curve of the first sampling time period includes a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is an IV curve in the first sampling time period and the first sampling voltage interval. The management system 13 may determine that the initial working state of the string group 111 is a fault state, that is, the first working state, in a manner that the sixth difference value corresponding to the first sampling time period is greater than the seventh preset difference value threshold and the seventh difference value is less than the eighth preset difference value threshold, or that the ratio between the sixth difference value and the seventh difference value corresponding to the first sampling time period is greater than the preset ratio threshold.

The management system 13 fits to obtain an IV curve of each sampling period of the group string 111 in N-1 sampling periods according to the received multiple groups of current-voltage values of the group string 111 in N-1 sampling periods under different sampling voltages. The management system 13 determines the number of IV curves that satisfy the condition that the ratio between the sixth difference value and the seventh difference value is greater than the preset ratio threshold value, or the sixth difference value is greater than the seventh preset difference value threshold value and the seventh difference value is less than the eighth preset difference value threshold value, among the N-1 IV curves of the N-1 sampling time periods. And when the number of the IV curves is larger than a preset number threshold value, determining that the string 111 has a fault.

Here, the specific implementation process of the management system 13 determining the sixth difference and the seventh difference corresponding to each sampling time period may refer to the specific implementation manner of the management system 13 determining the sixth difference and the seventh difference corresponding to the first sampling time period in the foregoing embodiment, and details are not described here.

In another possible embodiment, after obtaining the IV curve of the group string 111, the management system 13 calculates a second derivative function formula I ═ f "(U) of the IV curve of the group string 111 according to the function formula I ═ f (U) of the IV curve of the group string 111. Then, the management system 13 calculates a second derivative value of the third sample point on the IV curve of the string 111 according to I ═ f ″ (U). When the second derivative value of the third sampling point is the preset second derivative value (i.e. 0), the management system 13 indicates that the third sampling point is a distortion point on the IV curve of the string group 111, and determines that the string group 111 fails.

In the application, the power supply system 10 may determine whether a distortion point exists on the IV curve of the string group based on the second derivative value of the third sampling point on the IV curve of the string group of the management system 13, and further determine whether the string group is faulty, without relying on the component technology, which is also applicable to the string group produced by any manufacturer, and the applicability is strong.

Specifically, the management system 13 determines whether the second derivative value of the third sampling point on the IV curve of each sampling time period is 0, that is, it counts whether there is a sampling point with the second derivative value of 0 on the IV curve of each sampling time period, and counts the number of IV curves with the second derivative value of 0 on the IV curve in N IV curves of the sampling time periods. And when the number of the IV curves is larger than a preset number threshold value, determining that the string 111 has a fault.

In another embodiment, the management system 13 receives multiple sets of sampling data of the inverter 121 in the first sampling time period and the preset scanning sampling voltage interval, and fits to obtain an IV curve of the group string 111 in the first sampling time period, that is, an IV curve of the first sampling time period, according to the multiple sets of sampling data of the first sampling time period, where the IV curve of the first sampling time period includes a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is an IV curve in the first sampling time period and the first sampling voltage interval. The management system 13 may determine that the initial operating state of the string 111 is a fault state, i.e., a first operating state, by a manner that a sampling point having a second derivative value of 0 exists on the IV curve of the first sampling period.

The management system 13 fits to obtain an IV curve of each sampling period of the group string 111 in N-1 sampling periods according to the received multiple groups of current-voltage values of the group string 111 in N-1 sampling periods under different sampling voltages. The management system 13 determines the number of IV curves having the sampling point with the second derivative value of 0 on the I V curve among the N-1 IV curves for the N-1 sampling periods. And when the number of the IV curves is larger than a preset number threshold value, determining that the string 111 has a fault.

Here, a specific implementation process of the management system 13 determining the second derivative value of each sampling point on the IV curve of each sampling time period may refer to a specific implementation manner of the management system 13 determining the second derivative value of each sampling point on the IV curve of the first sampling time period in the foregoing embodiment, and details are not described here.

Referring to fig. 6, fig. 6 is a flow chart illustrating a fault identification method for a group string provided in the present application. The method for identifying the group string fault provided by the embodiment of the application is suitable for the management system in the power supply system shown in fig. 2. The fault identification method of the group string can comprise the following steps:

s101, receiving multiple groups of sampling data of a first group of sampling time periods which are serially connected under multiple sampling voltages and sent by a sampling device, and determining a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period.

And S102, determining whether the first group of strings are in failure or not according to the curvature value of the first sampling point on the working characteristic curve of the first sampling time period.

Specifically, after obtaining the IV curve of the first group (i.e., the IV curve of the first sampling time period) running in the first sampling time period, the management system calculates a first derivative functional formula I ═ f' (U) and a second derivative functional formula I ═ f ″ (U) of the IV curve of the first sampling time period according to the functional formula I ═ f (U) of the IV curve of the first sampling time period. Then, the management system calculates a first derivative value and a second derivative value of a first sampling point on the IV curve of the first sampling period according to I ═ f' (U) and I ═ f ″ (U), and further calculates a curvature value of the first sampling point

Wherein, f' (U)₁) And f' (U)₁) The first and second derivative values of the curve I V at the first sampling point for the first sampling period, respectively.

In an alternative embodiment, when there is a sampling point (first sampling point) with a curvature value greater than a preset curvature threshold value on the I V curve of the first sampling period, the management system indicates that the first sampling point is a distortion point on the IV curve of the first sampling period, and determines the first group of string faults.

In another optional embodiment, the management system determines a curve segment corresponding to a first sampling voltage interval on an IV curve of a first sampling time period as a first curve segment of the first sampling time period, and obtains a standard curve segment corresponding to the first curve segment of the first sampling time period, where the standard curve segment is a working characteristic curve acquired in the first sampling voltage interval in a normal group string, sampling voltages of a plurality of standard sampling points on the standard curve segment are respectively corresponding to and the same as sampling voltages of a plurality of sampling points on the first curve segment, and the first curve segment includes the first sampling point. And calculating the curvature value of each sampling point on the first curve segment according to the manner of calculating the curvature value of the first sampling point, and determining the similarity between the first curve segment and the standard curve segment according to the curvature value of each sampling point on the first curve segment and the standard curvature value of each standard sampling point on the standard curve segment. And when the similarity is smaller than a preset similarity threshold, the first curve segment is distorted, and the first group of string faults are determined.

In another optional embodiment, the management system determines a curve segment corresponding to a first sampling voltage interval on the IV curve of the first sampling time period as a first curve segment of the first sampling time period, and determines a curve segment corresponding to a second sampling voltage interval on the IV curve of the first sampling time period as a second curve segment of the first sampling time period. The first sampling voltage interval is adjacent to the second sampling voltage interval, the sampling voltage of each sampling point in the first sampling voltage interval is larger than that of each sampling point in the second sampling voltage interval, and the first curve segment comprises the first sampling point. The first sampling voltage interval and the second sampling voltage interval are both located in a preset scanning sampling voltage interval.

Then, the management system calculates the curvature values of the sampling points on the first curve segment of the first sampling time period and the second curve segment of the first sampling time period according to the manner of calculating the curvature values of the first sampling points, determines the average value of the curvature values of all the sampling points on the first curve segment of the first sampling time period as the first curvature characteristic value of the first curve segment of the first sampling time period, determines the average value of the curvature values of all the sampling points on the second curve segment of the first sampling time period as the second curvature characteristic value of the second curve segment of the first sampling time period, and calculates the difference between the first curvature characteristic value and the second curvature characteristic value to obtain a first difference. When the first difference is larger than a first preset difference threshold value, the change trend (namely descending) of the curvature characteristic values of the first curve segment and the second curve segment is more deviated from the change trend (namely ascending) of the curvature characteristic values of two adjacent curve segments of the normal string, and the IV curve of the first string is determined to be distorted, so that the fault of the first string is determined.

In yet another alternative embodiment, the management system may determine a curve segment corresponding to a first sampling voltage interval on the IV curve of the first sampling time period as a first curve segment of the first sampling time period, determine a curve segment corresponding to a second sampling voltage interval on the IV curve of the first sampling time period as a second curve segment of the first sampling time period, and determine a curve segment corresponding to a third sampling voltage interval on the IV curve of the first sampling time period as a third curve segment of the first sampling time period. The first curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a first sampling voltage interval and the first sampling time period, the second curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a second sampling voltage interval and the first sampling time period, the third curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a third sampling voltage interval and the first sampling time period, the second sampling voltage interval is adjacent to the first sampling voltage interval and the third sampling voltage interval respectively, the sampling voltage of each sampling point in the second sampling voltage interval is larger than that of each sampling point in the first sampling voltage interval, and is smaller than that of each sampling point in the third sampling voltage interval, and the first curve segment of the first sampling time period comprises the first sampling point.

And then, the management system calculates the curvature value of each sampling point on the first curve segment, the curvature value of each sampling point on the second curve segment and the curvature value of each sampling point on the third curve segment according to the manner of calculating the curvature value of the first sampling point. And determining the average value of the curvature values of all the points on the first curve segment of the first sampling time period as the first curvature characteristic value of the first curve segment of the first sampling time period, determining the average value of the curvature values of all the points on the second curve segment of the first sampling time period as the second curvature characteristic value of the second curve segment of the first sampling time period, and determining the average value of the curvature values of all the points on the third curve segment as the third curvature characteristic value of the third curve segment. And further calculating a difference value between the first curvature characteristic value and the second curvature characteristic value to obtain a first difference value, and calculating a difference value between the second curvature characteristic value and the third curvature characteristic value to obtain a second difference value. When the first difference is smaller than a second preset difference threshold and the second difference is larger than a third preset difference threshold, the variation trend (namely, increase and decrease) of the curvature characteristic values of the first curve segment, the second curve segment and the third curve segment is larger than the variation trend (namely, increase all the time) of the curvature characteristic values of three adjacent curve segments of the normal group string, and the first group string fault is determined.

Further, the management system can also determine whether the string has a fault according to the working characteristic curves of the plurality of sampling time periods, and the specific mode is as follows:

in an optional embodiment, the management system fits to obtain an IV curve of the first string in each of N sampling periods according to received multiple sets of current-voltage values of the first string in the N sampling periods under different sampling voltages.

In an optional embodiment, the management system determines whether a first sampling point with a curvature value larger than a preset curvature threshold exists on an IV curve of each sampling time period, counts the number of IV curves with the first sampling point on the IV curve in N IV curves of the N sampling time periods, and determines a first group of string faults when the number of the IV curves is larger than a preset number threshold.

And the management system acquires the standard curve segment corresponding to the first curve segment of each sampling time period, and determines the similarity between the first curve segment of each sampling time period and the standard curve segment according to the curvature value of each sampling point on the first curve segment of each sampling time period and the standard curvature value of each standard sampling point on the standard curve segment corresponding to the first curve segment of each sampling time period. And counting the number of the first curve segments with the similarity smaller than a preset similarity threshold value in N first curve segments in N sampling time periods, and determining a first group of string faults when the number of the first curve segments is larger than the preset number threshold value.

The management system determines a first curvature characteristic value of the first curve segment of each sampling time period according to the curvature value of each sampling point on the first curve segment of each sampling time period, and determines a second curvature characteristic value of the second curve segment of each sampling time period according to the curvature value of each sampling point on the second curve segment of each sampling time period. And calculating a first difference value between the first curvature characteristic value and the second curvature characteristic value of each sampling time period, and counting the number of IV curves of which the first difference value is greater than a first preset difference value threshold value in N IV curves of the N sampling time periods. And when the number of the IV curves is larger than a preset number threshold value, determining that the first group of strings has faults.

The management system determines a first curvature characteristic value of the first curve segment of each sampling time period according to the curvature value of each sampling point on the first curve segment of each sampling time period, determines a second curvature characteristic value of the second curve segment of each sampling time period according to the curvature value of each sampling point on the second curve segment of each sampling time period, and determines a third curvature characteristic value of the third curve segment of each sampling time period according to the curvature value of each sampling point on the third curve segment of each sampling time period. And calculating a first difference value between the first curvature characteristic value and the second curvature characteristic value of each sampling time period and a second difference value between the second curvature characteristic value and the third curvature characteristic value, and counting the number of IV curves of which the first difference value is smaller than a second preset difference threshold value and the second difference value is larger than a third preset difference threshold value in N IV curves of the N sampling time periods. And when the number of the IV curves is larger than a preset number threshold value, determining that the first group of strings has faults.

In another embodiment, the management system fits the IV curve of the first set of strings over the first sampling period, i.e., the IV curve of the first sampling period, based on the plurality of sets of sample data of the first set of strings over the first sampling period. The management system may determine that the initial operating state of the first group string is a fault state by a curvature value of a first sampling point on the IV curve of the first sampling period being greater than a preset curvature threshold, or by a similarity between a first curve segment on the IV curve of the first sampling period and a standard curve segment corresponding to the first curve segment being less than a preset similarity threshold, or by a first difference between a first curvature characteristic value of the first curve segment of the first sampling period and a second curvature characteristic value of the second curve segment being greater than a first preset difference threshold, or by a first difference between the first curvature characteristic value of the first curve segment of the first sampling period and the second curvature characteristic value of the second curve segment being less than a second preset difference threshold, and a second difference between the second curvature characteristic value of the second curve segment and a third curvature characteristic value of the third curve segment being greater than a third preset difference threshold, i.e. the first operating state.

And then, when the management system determines that the initial working state of the first group of strings is a fault state, acquiring multiple groups of sampling data of the first group of strings in N-1 sampling time periods under multiple sampling voltages. And fitting to obtain an IV curve of the first group of strings in each sampling time period in the N-1 sampling time periods according to a plurality of groups of current and voltage values of the first group of strings in the N-1 sampling time periods under different sampling voltages. The management system determines the number of IV curves which meet the condition that the curvature value of a first sampling point is larger than a preset curvature threshold value, or the similarity between a first curve segment of each sampling time period and a standard curve segment corresponding to the first curve segment is smaller than a preset similarity threshold value, or a first difference between a first curvature characteristic value of the first curve segment of each sampling time period and a second curvature characteristic value of a second curve segment is larger than a first preset difference threshold value, or a first difference between the first curvature characteristic value of the first curve segment of each sampling time period and the second curvature characteristic value of the second curve segment is smaller than a second preset difference threshold value and a second difference between the second curvature characteristic value of the second curve segment and a third curvature characteristic value of a third curve segment is larger than a third preset difference threshold value in N-1 IV curves of the N-1 sampling time periods, when the number of the IV curves is larger than the preset number threshold value, a first set of string faults is determined.

In a specific implementation, the specific implementation process that the management system determines whether the first group string is faulty according to the curvature value of the first sampling point on the working characteristic curve of the first sampling time period may refer to a specific implementation manner that the management system 13 determines whether the group string 111 is faulty according to the curvature value of the first sampling point on the working characteristic curve of the first sampling time period in the foregoing embodiment, and details are not repeated here.

In the application, the management system can determine whether the IV curve of the string group is distorted or not through the curvature value of the first sampling point on the IV curve of the string group, the curvature value of each sampling point on the first curve segment, the curvature characteristic values of two adjacent curve segments or the curvature characteristic values of three adjacent curve segments, and then determine whether the string group is in fault or not without depending on the assembly technology, namely, the management system is suitable for the string group produced by any manufacturer and has strong applicability.

Referring to fig. 7, fig. 7 is another schematic flow chart of the fault identification method for group strings provided in the present application. The method for identifying the group string fault provided by the embodiment of the application is suitable for the management system in the power supply system shown in fig. 2. The fault identification method of the group string can comprise the following steps:

s201, receiving multiple groups of sampling data of a first group of sampling time periods which are serially connected under multiple sampling voltages and sent by a sampling device, and determining a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period.

The working characteristic curve of the first sampling time period comprises a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a first sampling voltage interval.

In some possible embodiments, after obtaining the IV curve of the first sampling time period, the management system determines a curve segment corresponding to the first sampling voltage interval on the IV curve of the first sampling time period as the first curve segment of the first sampling time period.

S202, determining whether the first group of strings has faults or not according to the distance deviation value from each sampling point on the first curve segment of the first sampling time period to the first straight line corresponding to the first curve segment of the first sampling time period.

Each sampling point corresponds to each sampling voltage in a first sampling voltage interval one by one, and the first straight line is determined by an initial sampling point and an end sampling point of the first curve segment.

Specifically, the management system calculates a first straight line l of the first curve segment according to a current-voltage value corresponding to an initial sampling point and a current-voltage value corresponding to an end sampling point on the first curve segment of the first sampling time period₁Has a linear equation of A₁U+B₁I+C ₁0. Then, according to the formula

Calculating each sample point (U) on the first curve segment_i,I_i) To l₁Distance d of_1iI.e. each sample point to l₁Is calculated from the distance deviation value. The management system determines a first set of string faults when the second sample point is not present on the first curve segment. The second sampling point is a boundary point of a first sub-curve segment and a second sub-curve segment, wherein the first sub-curve segment is a curve segment of which the sampling voltage on the first curve segment is smaller than the sampling voltage of the second sampling point, the distance deviation value of each sampling point on the first sub-curve segment increases along with the increase of the sampling voltage, the second sub-curve segment is a curve segment of which the sampling voltage on the first curve segment is larger than the sampling voltage of the second sampling point, and the distance deviation value of each sampling point on the second sub-curve segment decreases along with the increase of the sampling voltage.

Further, the management system can also determine whether the first group of strings has a fault according to the working characteristic curves of the plurality of sampling time periods, and the specific manner is as follows:

Specifically, the management system determines a distance deviation value from each sampling point on the first curve segment of each sampling time period to a first straight line corresponding to the first curve segment of each sampling time period, and determines whether a second sampling point exists on the first curve segment of each sampling time period according to the distance deviation value of each sampling point on the first curve segment of each sampling time period, so as to count the number of the first curve segments without the second sampling point in the N first curve segments of the N sampling time periods. And when the number of the first curve segments is greater than a preset number threshold, determining a first group of string faults, wherein a first straight line corresponding to the first curve segment of each sampling time period is determined by an initial sampling point and an end sampling point of the first curve segment of each sampling time period.

In another embodiment, the management system fits the IV curve of the first string at the first sampling time period, that is, the IV curve of the first sampling time period, according to the multiple sets of sample data of the first string at the first sampling time period, where the IV curve of the first sampling time period includes a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is an IV curve within the first sampling time period and the first sampling voltage interval. The management system can determine that the initial working state of the first group of strings is a fault state, namely a first working state, in a mode that a second sampling point does not exist on a first curve segment of a first sampling time period.

And then, when the management system determines that the initial working state of the first group of strings is a fault state, acquiring multiple groups of sampling data of the first group of strings in N-1 sampling time periods under multiple sampling voltages, and fitting to obtain an IV curve of the first group of strings in each sampling time period in the N-1 sampling time periods according to multiple groups of current and voltage values of the first group of strings in the N-1 sampling time periods under different sampling voltages. The management system determines the number of IV curves of which the second sampling point does not exist on the first curve segment in the N-1 IV curves of the N-1 sampling time segments. And when the number of the IV curves is larger than a preset number threshold value, determining that the first group of strings has faults.

In a specific implementation, the specific implementation process that the management system determines whether the first group string is faulty according to the distance deviation value of each sampling point on the first curve segment of the first sampling time period may refer to a specific implementation manner that the management system 13 determines whether the group string 111 is faulty according to the distance deviation value of each sampling point on the first curve segment of the first sampling time period in the foregoing embodiment, and details are not repeated here.

In the application, the management system can determine whether the IV curve of the string group is distorted or not through the variation trend of the distance characteristic value of each sampling point on the first curve segment in the IV curve of the string group, and further determine whether the string group is in fault or not without depending on an assembly technology, so that the management system is also suitable for the string group produced by any manufacturer and has strong applicability.

Referring to fig. 8, fig. 8 is another schematic flow chart of the fault identification method for group strings provided in the present application. The method for identifying the group string fault provided by the embodiment of the application is suitable for the management system in the power supply system shown in fig. 2. The fault identification method of the group string can comprise the following steps:

s301, receiving multiple groups of sampling data of a first group of sampling time periods which are serially connected under multiple sampling voltages and sent by a sampling device, and determining a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period.

After obtaining the IV curve of the first sampling time period, the management system divides the IV curve of the first sampling time period into a plurality of curve segments according to a plurality of sampling voltage intervals.

S302, determining first-order derivative characteristic values of the curve segments in the first sampling time period, and determining whether the first group of strings are failed according to the first-order derivative characteristic values of the curve segments in the first sampling time period.

In some possible embodiments, the management system calculates the first derivative function formula I ═ f' (U) of the IV curve for the first sampling period according to the function formula I ═ f (U) of the IV curve for the first sampling period. And further, calculating to obtain a first derivative value of each sampling point on each curve segment of the first sampling time period according to the I ═ f' (U), and determining an average value of the first derivative values of each sampling point on each curve segment as a first derivative characteristic value of each curve segment of the first sampling time period. And further determining whether the first group of strings are failed according to the characteristic value of the first derivative of each curve segment.

Wherein the plurality of curve segments of the first sampling time period includes a first curve segment of the first sampling time period, a second curve segment of the first sampling time period, and a third curve segment of the first sampling time period, the first curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a first sampling voltage interval, the second curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a second sampling voltage interval, the third curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a third sampling voltage interval, the second sampling voltage interval is adjacent to the first sampling voltage interval and the third sampling voltage interval respectively, and the sampling voltage of each sampling point in the second sampling voltage interval is greater than that of each sampling point in the first sampling voltage interval and is less than that of each sampling point in the third sampling voltage interval.

After calculating and obtaining a first derivative characteristic value of a first curve segment of a first sampling time period, a second first derivative characteristic value of a second curve segment of the first sampling time period and a third first derivative characteristic value of a third curve segment of the first sampling time period, the management system determines whether the first group of strings has faults or not according to a sixth difference value between the first derivative characteristic value and the second first derivative characteristic value and a seventh difference value between the second first derivative characteristic value and the third first derivative characteristic value.

In an alternative embodiment, the management system calculates a ratio between the sixth difference and the seventh difference, and determines that the first group of string faults occurs when the ratio is greater than a preset ratio threshold, indicating that a distortion has occurred in the first, second, and third curve segments.

In another optional embodiment, when the sixth difference is greater than the seventh preset difference threshold and the seventh difference is less than the eighth preset difference threshold, the management system indicates that the variation trend (i.e., decreasing first and then increasing) of the first-order derivative characteristic values of the first, second, and third curve segments is deviated from the variation trend (i.e., decreasing always) of the first-order derivative characteristic values of the three adjacent curve segments of the normal string group, and determines that the first string group is faulty.

Specifically, the management system determines a first derivative characteristic value of a first curve segment, a second first derivative characteristic value of a second curve segment, and a third first derivative characteristic value of a third curve segment in each sampling time period, and determines whether the first group of strings has a fault according to a sixth difference between the first derivative characteristic value and the second first derivative characteristic value in each sampling time period, and a seventh difference between the second first derivative characteristic value and the third first derivative characteristic value.

In another embodiment, the management system fits the IV curve of the first string at the first sampling time period, that is, the IV curve of the first sampling time period, according to the multiple sets of sample data of the first string at the first sampling time period, where the IV curve of the first sampling time period includes a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is an IV curve within the first sampling time period and the first sampling voltage interval. The management system may determine that the initial working state of the first group of strings is a fault state, that is, the first working state, in a manner that a sixth difference value corresponding to the first sampling period is greater than a seventh preset difference value threshold and the seventh difference value is less than an eighth preset difference value threshold, or a ratio between the sixth difference value and the seventh difference value corresponding to the first sampling period is greater than a preset ratio value threshold.

And then, when the management system determines that the initial working state of the first group of strings is a fault state, acquiring multiple groups of sampling data of the first group of strings in N-1 sampling time periods under multiple sampling voltages, and fitting to obtain an IV curve of the first group of strings in each sampling time period in the N-1 sampling time periods according to multiple groups of current and voltage values of the first group of strings in the N-1 sampling time periods under different sampling voltages. And the management system determines the number of IV curves which meet the conditions that the ratio of the sixth difference value to the seventh difference value is greater than a preset ratio threshold value or the sixth difference value is greater than a seventh preset difference value threshold value and the seventh difference value is less than an eighth preset difference value threshold value in the N-1 IV curves of the N-1 sampling time periods. And when the number of the IV curves is larger than a preset number threshold value, determining that the first group of strings has faults.

In a specific implementation, the specific implementation process that the management system determines whether the first group string is faulty according to the first derivative characteristic value of each curve segment in the first sampling time period may refer to a specific implementation manner that the management system 13 determines whether the group string 111 is faulty according to the first derivative characteristic value of each curve segment in the first sampling time period in the foregoing embodiment, and details are not described here again.

In the application, the management system can determine whether the IV curve of the string is distorted or not through the variation trend of the first derivative characteristic values of three adjacent curve sections on the IV curve of the string, and further determine whether the string is in fault or not without depending on an assembly technology, and the management system is also suitable for strings produced by any manufacturer and has strong applicability.

Referring to fig. 9, fig. 9 is a schematic flow chart of a fault identification method for a group string provided in the present application. The method for identifying the group string fault provided by the embodiment of the application is suitable for the management system in the power supply system shown in fig. 2. The fault identification method of the group string can comprise the following steps:

s401, receiving multiple groups of sampling data of a first sampling time period of a first group of strings under multiple sampling voltages, which are sent by a sampling device, and determining a working characteristic curve of the first group of strings based on the multiple groups of sampling data of the first sampling time period.

S402, determining whether the first group of strings are in fault according to the second derivative value of the third sampling point on the working characteristic curve of the first sampling time period.

In some possible embodiments, after obtaining the IV curve for the first sampling period, the management system calculates the second derivative function of the IV curve for the first sampling period according to the function formula I ═ f (U) of the IV curve for the first sampling period. And then, the management system calculates a second derivative value of a third sampling point on the IV curve of the first sampling time period according to the I ═ f' (U). When the second derivative value of the third sampling point is a point of a preset second derivative value (namely 0), the management system indicates that the third sampling point is a distortion point on an IV curve of the first sampling time period, and determines a first group of string faults.

Specifically, the management system determines whether the second derivative value of the third sampling point on the IV curve of each sampling time period is 0, that is, counts whether there is a sampling point with the second derivative value of 0 on the I V curve of each sampling time period, and counts the number of IV curves of the sampling points with the second derivative value of 0 on the IV curve in the N IV curves of the N sampling time periods. And when the number of the IV curves is larger than a preset number threshold value, determining that the first group of strings has faults.

In another embodiment, the management system fits the IV curve of the first string at the first sampling time period, that is, the IV curve of the first sampling time period, according to the multiple sets of sample data of the first string at the first sampling time period, where the IV curve of the first sampling time period includes a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is an IV curve within the first sampling time period and the first sampling voltage interval. The management system may determine that the initial operating state of the first group of strings is a fault state, i.e., a first operating state, in a manner that a sampling point having a second derivative value of 0 exists on the I V curve of the first sampling period.

And then, when the management system determines that the initial working state of the first group of strings is a fault state, acquiring multiple groups of sampling data of the first group of strings in N-1 sampling time periods under multiple sampling voltages, and fitting to obtain an IV curve of the first group of strings in each sampling time period in the N-1 sampling time periods according to multiple groups of current and voltage values of the first group of strings in the N-1 sampling time periods under different sampling voltages. The management system determines the number of IV curves of sampling points with a second derivative value of 0 in the N-1 IV curves of the N-1 sampling time periods. And when the number of the IV curves is larger than a preset number threshold value, determining that the first group of strings has faults.

In a specific implementation, the specific implementation process that the management system determines whether the first group string is faulty or not according to the second derivative value of the third sampling point on the working characteristic curve of the first sampling time period may be referred to in the above embodiment, and details of the specific implementation manner that the management system 13 determines whether the group string 111 is faulty or not according to the second derivative value of the third sampling point on the working characteristic curve of the first sampling time period are not repeated here.

In the application, the management system can determine whether a distortion point exists on the IV curve of the string group through the second derivative value of the third sampling point on the IV curve of the string group, and further determine whether the string group is in fault without depending on an assembly technology, so that the management system is also suitable for the string group produced by any manufacturer and has strong applicability.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A power supply system is characterized by comprising a management system, a sampling device, an inverter and a first group of strings, wherein the sampling device is in communication connection with the management system;

the sampling device is used for acquiring a plurality of working parameters of the first group of strings under a plurality of sampling voltages to obtain a plurality of groups of sampling data of a first sampling time period, and sending the plurality of groups of sampling data of the first sampling time period to the management system;

the management system is used for receiving multiple groups of sampling data of the first sampling time period and determining a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period, wherein each sampling point on the working characteristic curve of the first sampling time period corresponds to each sampling voltage one by one; and determining whether the first group of strings are failed according to the curvature value of a first sampling point on the working characteristic curve of the first sampling time period.

2. The power supply system of claim 1, wherein the management system is configured to determine the first set of string faults when the curvature value of the first sample point is greater than a preset curvature threshold.

3. The power supply system of claim 1, wherein the operating characteristic curve comprises a first curve segment, the first curve segment being an operating characteristic curve sampled at a first sampling voltage interval, the first curve segment comprising the first sampling point;

the management system is used for determining the similarity between the first curve segment and the standard curve segment according to the curvature value of each sampling point on the first curve segment and the standard curvature value of each standard sampling point on the standard curve segment; and when the similarity is smaller than a preset similarity threshold, determining the first group of string faults, wherein the sampling voltages of the plurality of standard sampling points on the standard curve segment are respectively and correspondingly the same as the sampling voltages of the plurality of sampling points on the first curve segment.

4. The power supply system according to claim 1, wherein the operating characteristic curve comprises a first curve segment and a second curve segment, wherein the first curve segment is an operating characteristic curve sampled in a first sampling voltage interval, the second curve segment is an operating characteristic curve sampled in a second sampling voltage interval, the first sampling voltage interval is adjacent to the second sampling voltage interval, and the sampling voltage of each sampling point in the first sampling voltage interval is greater than the sampling voltage of each sampling point in the second sampling voltage interval, and the first curve segment comprises the first sampling point;

the management system is used for determining a first curvature characteristic value of the first curve segment according to the curvature value of each sampling point on the first curve segment and determining a second curvature characteristic value of the second curve segment according to the curvature value of each sampling point on the second curve segment; determining the first set of string faults when a first difference between the first curvature characteristic value and the second curvature characteristic value is greater than a first preset difference threshold.

5. The power supply system of claim 1, wherein said operating characteristic curve comprises a first curve segment, a second curve segment, and a third curve segment, wherein the first curve segment is a working characteristic curve obtained by sampling in a first sampling voltage interval, the second curve segment is a working characteristic curve obtained by sampling in a second sampling voltage interval, the third curve segment is a working characteristic curve obtained by sampling in a third sampling voltage interval, the second sampling voltage interval is adjacent to the first sampling voltage interval and the third sampling voltage interval respectively, the sampling voltage of each sampling point in the second sampling voltage interval is greater than that of each sampling point in the first sampling voltage interval, the first curve segment comprises a first sampling point and a second sampling point, and the first sampling point is smaller than the sampling voltage of each sampling point in the third sampling voltage interval;

the management system is used for determining a first curvature characteristic value of the first curve segment according to the curvature value of each sampling point on the first curve segment, determining a second curvature characteristic value of the second curve segment according to the curvature value of each sampling point on the second curve segment, and determining a third curvature characteristic value of the third curve segment according to the curvature value of each sampling point on the third curve segment;

determining the first group of string faults when a first difference between the first curvature characteristic value and the second curvature characteristic value is less than a second preset difference threshold and a second difference between the second curvature characteristic value and the third curvature characteristic value is greater than a third preset difference threshold.

6. A power supply system as claimed in claim 4 or 5, characterized in that the management system is configured to determine the first curvature characteristic value as the mean value of the curvature values of all sampling points on the first curve segment.

7. Power supply system according to claims 1-6, characterized in thatIn that the curvature value of the first sampling point

Wherein, the f' is U₁) And f' (U)₁) Respectively, a first derivative value and a second derivative value of the working characteristic curve at the first sampling point.

8. The power supply system of any one of claims 1-7, wherein the management system is configured to:

receiving a plurality of groups of sampling data of the first group of sampling time periods which are serially connected under a plurality of sampling voltages, and determining a working characteristic curve of each sampling time period based on the plurality of groups of sampling data of each sampling time period, wherein the N sampling time periods comprise the first time period, the N sampling time periods are different, and each sampling point on the working characteristic curve of each sampling time period corresponds to each sampling voltage one by one;

and determining whether the first group of strings are in failure or not according to the curvature value of the first sampling point on the working characteristic curve of each sampling time period.

9. The power supply system of claim 8, wherein the N sampling periods comprise a second sampling period, and wherein an interval duration between the second sampling period and the first sampling period is greater than a preset interval duration threshold.

10. The power supply system of claim 8, wherein the N sampling periods comprise N-1 third sampling periods;

the management system is used for receiving multiple groups of sampling data of the first sampling time period of the first group of strings under multiple sampling voltages and determining a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period;

and determining an initial working state of the first group of strings according to a curvature value of a first sampling point on a working characteristic curve of the first sampling time period, and receiving multiple groups of sampling data of the first group of strings in the N-1 third sampling time periods when the initial working state is the first working state.

11. A power supply system is characterized by comprising a management system, a sampling device, an inverter and a first group of strings, wherein the sampling device is in communication connection with the management system;

the management system is configured to receive multiple sets of sampling data of the first sampling time period, and determine a working characteristic curve of the first sampling time period based on the multiple sets of sampling data of the first sampling time period, where the working characteristic curve of the first sampling time period includes a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a first sampling voltage interval;

and determining whether the first group of strings has a fault according to the distance deviation value from each sampling point on a first curve segment of the first sampling time period to a first straight line corresponding to the first curve segment of the first sampling time period, wherein each sampling point corresponds to each sampling voltage in a first sampling voltage interval one by one, and the first straight line is determined by the initial sampling point and the final sampling point of the first curve segment.

12. The power supply system of claim 11 wherein the management system is configured to determine the first set of string faults when a second sampling point is not present on the first curve segment, wherein the second sampling point is a demarcation point between a first sub-curve segment and a second sub-curve segment, wherein the first sub-curve segment is a curve segment having a sampled voltage on the first curve segment that is less than a sampled voltage of the second sampling point, and wherein a distance deviation value of each sampling point on the first sub-curve segment increases with increasing sampled voltage, wherein the second sub-curve segment is a curve segment having a sampled voltage on the first curve segment that is greater than a sampled voltage of the second sampling point, and wherein the distance deviation value of each sampling point on the second sub-curve segment decreases with increasing sampled voltage.

13. The power supply system according to claim 11 or 12, wherein the management system is configured to:

receiving a plurality of groups of sampling data of the first group of sampling time periods which are serially connected under a plurality of sampling voltages, and determining a working characteristic curve of each sampling time period based on the plurality of groups of sampling data of each sampling time period, wherein the N sampling time periods comprise the first time period, the N sampling time periods are different from each other, the working characteristic curve of each sampling time period comprises a first curve segment of each sampling time period, and the first curve segment of each sampling time period is a working characteristic curve obtained by sampling in the first sampling voltage interval;

and determining whether the first group of strings has a fault according to the distance deviation value from each sampling point on the first curve segment of each sampling time period to the first straight line corresponding to the first curve segment of each sampling time period, wherein the first straight line corresponding to the first curve segment of each sampling time period is determined by the initial sampling point and the final sampling point of the first curve segment of each sampling time period.

14. The power supply system of claim 13, wherein the N sampling periods comprise a second sampling period, and wherein an interval duration between the second sampling period and the first sampling period is greater than a preset interval duration threshold.

15. The power supply system of claim 13, wherein the N sampling periods comprise N-1 third sampling periods;

the management system is used for receiving multiple groups of sampling data of the first sampling time period of the first group of strings under multiple sampling voltages, and determining a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period, wherein the working characteristic curve of the first sampling time period comprises a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is a working characteristic curve obtained by sampling in the first sampling voltage interval;

and determining an initial working state of the first group of strings according to the distance deviation from each sampling point on the first sampling time period to a first straight line corresponding to a first curve segment of the first sampling time period, and receiving multiple groups of sampling data of the first group of strings under the N-1 third sampling time periods when the initial working state is the first working state.

16. A power supply system is characterized by comprising a management system, a sampling device, an inverter and a first group of strings, wherein the sampling device is in communication connection with the management system;

the management system is configured to receive multiple sets of sampling data of the first sampling time period, and determine a working characteristic curve of the first sampling time period based on the multiple sets of sampling data of the first sampling time period, where the working characteristic curve of the first sampling time period includes multiple curve segments of the first sampling time period, and each curve segment of the first sampling time period is a working characteristic curve obtained by sampling in each sampling voltage interval;

and determining the first-order derivative characteristic value of each curve segment of the first sampling time period, and determining whether the first group of strings is failed according to the first-order derivative characteristic value of each curve segment of the first sampling time period.

17. The power supply system according to claim 16, wherein the plurality of curve segments include a first curve segment, a second curve segment and a third curve segment, wherein the first curve segment is an operating characteristic curve sampled in a first sampling voltage interval, the second curve segment is an operating characteristic curve sampled in a second sampling voltage interval, the third curve segment is an operating characteristic curve sampled in a third sampling voltage interval, the second sampling voltage interval is respectively adjacent to the first sampling voltage interval and the third sampling voltage interval, and the sampling voltage of each sampling point in the second sampling voltage interval is greater than the sampling voltage of each sampling point in the first sampling voltage interval and less than the sampling voltage of each sampling point in the third sampling voltage interval;

the management system is configured to determine whether the first set of strings is faulty based on a sixth difference between the first derivative characteristic value of the first curve segment and the first derivative characteristic value of the second curve segment, and a seventh difference between the first derivative characteristic value of the second curve segment and the first derivative characteristic value of the third curve segment.

18. The power supply system of claim 17, wherein the management system is configured to determine that the first group of strings is faulty when a ratio between the sixth difference and the seventh difference is greater than a preset ratio threshold.

19. The power system of claim 17, wherein the management system is configured to determine that the first group of strings is faulty when the sixth difference is greater than a seventh preset difference threshold and the seventh difference is less than an eighth preset difference threshold.

20. A power supply system according to any one of claims 16 to 19, wherein the management system is configured to determine a first derivative value for each sample point on each curve segment, and to determine a mean of the first derivative values for all sample points on each curve segment as the first derivative characteristic value for each curve segment.

21. The power supply system of any one of claims 16-20, wherein the management system is configured to:

receiving a plurality of groups of sampling data of the first group of sampling time periods which are serially connected under a plurality of sampling voltages, and determining a working characteristic curve of each sampling time period based on the plurality of groups of sampling data of each sampling time period, wherein the N sampling time periods comprise the first time period, the N sampling time periods are different from each other, the working characteristic curve of each sampling time period comprises a plurality of curve segments of each sampling time period, and each curve segment of each sampling time period is a working characteristic curve obtained by sampling in each sampling voltage interval;

and determining the first-order derivative characteristic value of each curve segment of each sampling time period, and determining whether the first group of strings have faults or not according to the first-order derivative characteristic value of each curve segment of each sampling time period.

22. The power supply system of claim 21, wherein the N sampling periods comprise a second sampling period, and wherein an interval duration between the second sampling period and the first sampling period is greater than a preset interval duration threshold.

23. The power supply system of claim 21, wherein the N sampling periods comprise N-1 third sampling periods;

the management system is used for receiving multiple groups of sampling data of the first sampling time period of the first group of strings under multiple sampling voltages and determining an operating characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period, wherein the operating characteristic curve of the first sampling time period comprises multiple curve segments of the first sampling time period;

and determining an initial working state of the first group of strings according to the first derivative characteristic value of each curve segment of the first sampling time period, and receiving multiple groups of sampling data of the first group of strings in the N-1 third sampling time periods when the initial working state is the first working state.

24. A power supply system is characterized by comprising a management system, a sampling device, an inverter and a first group of strings, wherein the sampling device is in communication connection with the management system;

the management system is used for receiving multiple groups of sampling data of the first sampling time period and determining a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period, wherein each sampling point on the working characteristic curve of the first sampling time period corresponds to each sampling voltage one by one;

and determining whether the first group of strings has faults or not according to the second derivative value of a third sampling point on the working characteristic curve of the first sampling time period.

25. The power supply system of claim 24, wherein the management system is configured to determine the first set of string faults when the second derivative value of the third sample point is 0.

26. The power supply system of claim 24 or 25, wherein the management system is configured to:

and determining whether the first group of strings has faults or not according to the second derivative value of the third sampling point on the working characteristic curve of each sampling time period.

27. The power supply system of claim 26, wherein the N sampling periods comprise a second sampling period, and wherein an interval duration between the second sampling period and the first sampling period is greater than a preset interval duration threshold.

28. The power supply system of claim 26, wherein said N sampling periods comprise N-1 third sampling periods;

and determining an initial working state of the first group of strings according to a second derivative value of a third sampling point on the working characteristic curve of the first sampling time period, and receiving multiple groups of sampling data of the first group of strings in the N-1 third sampling time periods when the initial working state is the first working state.

29. The method is characterized by being applied to a power supply system, wherein the power supply system comprises a sampling device, an inverter and a first group string connected with the inverter;

the method comprises the following steps:

receiving multiple groups of sampling data of a first sampling time period of the first group of sampling voltages in series sent by the sampling device, and determining a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period, wherein each sampling point on the working characteristic curve of the first sampling time period corresponds to each sampling voltage one by one;

and determining whether the first group of strings are failed according to the curvature value of a first sampling point on the working characteristic curve of the first sampling time period.

30. The method of claim 29, wherein said determining whether the first set of strings is faulty based on the curvature value of the first sample point on the operating characteristic curve of the first sample period comprises:

and when the curvature value of the first sampling point is larger than a preset curvature threshold value, determining that the first group of strings has faults.

31. The method of claim 29, wherein the operating characteristic comprises a first curve segment, the first curve segment being an operating characteristic sampled at a first sampling voltage interval, the first curve segment comprising the first sampling point;

the determining whether the first group of strings is faulty according to the curvature value of the first sampling point on the working characteristic curve of the first sampling time period includes:

determining the similarity between the first curve segment and a standard curve segment according to the curvature value of each sampling point on the first curve segment and the standard curvature value of each standard sampling point on the standard curve segment, wherein the sampling voltages of a plurality of standard sampling points on the standard curve segment are respectively and correspondingly the same as the sampling voltages of a plurality of sampling points on the first curve segment;

and when the similarity is smaller than a preset similarity threshold value, determining that the first group of strings has faults.

32. The method of claim 29, wherein the operating characteristic curve comprises a first curve segment and a second curve segment, wherein the first curve segment is an operating characteristic curve sampled in a first sampling voltage interval, the second curve segment is an operating characteristic curve sampled in a second sampling voltage interval, the first sampling voltage interval is adjacent to the second sampling voltage interval, and the sampling voltage of each sampling point in the first sampling voltage interval is greater than the sampling voltage of each sampling point in the second sampling voltage interval, and the first curve segment comprises the first sampling point;

said determining whether said first set of strings is faulty based on a curvature value of a first sample point on a first curve segment of said first sample time period comprises:

determining a first curvature characteristic value of the first curve segment according to the curvature value of each sampling point on the first curve segment, and determining a second curvature characteristic value of the second curve segment according to the curvature value of each sampling point on the second curve segment;

determining the first set of string faults when a first difference between the first curvature characteristic value and the second curvature characteristic value is greater than a first preset difference threshold.

33. The method of claim 29 wherein the operating characteristic curve includes a first curve segment, a second curve segment, and a third curve segment, wherein the first curve segment is a working characteristic curve obtained by sampling in a first sampling voltage interval, the second curve segment is a working characteristic curve obtained by sampling in a second sampling voltage interval, the third curve segment is a working characteristic curve obtained by sampling in a third sampling voltage interval, the second sampling voltage interval is adjacent to the first sampling voltage interval and the third sampling voltage interval respectively, the sampling voltage of each sampling point in the second sampling voltage interval is greater than that of each sampling point in the first sampling voltage interval, the first curve segment comprises a first sampling point and a second sampling point, and the first sampling point is smaller than the sampling voltage of each sampling point in the third sampling voltage interval;

determining a first curvature characteristic value of the first curve segment according to the curvature value of each sampling point on the first curve segment, determining a second curvature characteristic value of the second curve segment according to the curvature value of each sampling point on the second curve segment, and determining a third curvature characteristic value of the third curve segment according to the curvature value of each sampling point on the third curve segment;

34. The method of claim 32 or 33, wherein said determining a first curvature characteristic value for the first curve segment from the curvature values of the sample points on the first curve segment comprises:

and determining the mean value of the curvature values of all the sampling points on the first curve segment as the first curvature characteristic value.

35. The method of claims 29-34, wherein the curvature value of the first sample point

Wherein, the f' (U)₁) And f' (U)₁) Respectively, a first derivative value and a second derivative value of the working characteristic curve at the first sampling point.

36. The method of claims 29-35, wherein the receiving a plurality of sets of sample data sent by the inverter for a first set of sample periods of the first string at a plurality of sample voltages and determining an operating profile for the first sample period based on the plurality of sets of sample data for the first sample period comprises:

37. The method of claim 36, wherein the N sampling periods comprise a second sampling period, and wherein a duration of an interval between the second sampling period and the first sampling period is greater than a preset interval duration threshold.

38. The method of claim 36, wherein the N sampling periods comprise N-1 third sampling periods;

the receiving a plurality of sets of sample data for N sample time periods of the first set of strings at a plurality of sample voltages includes:

receiving a plurality of groups of sampling data of the first sampling time period of the first group of strings under a plurality of sampling voltages, and determining an operating characteristic curve of the first sampling time period based on the plurality of groups of sampling data of the first sampling time period;

39. The method is characterized by being applied to a power supply system, wherein the power supply system comprises a sampling device, an inverter and a first group string connected with the inverter;

the method comprises the following steps:

receiving multiple groups of sampling data of a first sampling time period of the first group of strings under multiple sampling voltages, which are sent by the sampling device, and determining a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period, wherein the working characteristic curve of the first sampling time period comprises a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is a working characteristic curve obtained by sampling in a first sampling voltage interval;

40. The method of claim 39, wherein said determining whether the first set of strings is faulty based on a distance deviation value of each sample point on the first curved segment of the first sampling time period from a first straight line corresponding to the first curved segment of the first sampling time period comprises:

determining the first group of string faults when a second sampling point does not exist on the first curve segment, wherein the second sampling point is a boundary point of a first sub-curve segment and a second sub-curve segment, the first sub-curve segment is a curve segment of which the sampling voltage on the first curve segment is smaller than the sampling voltage of the second sampling point, the distance deviation value of each sampling point on the first sub-curve segment increases along with the increase of the sampling voltage, the second sub-curve segment is a curve segment of which the sampling voltage on the first curve segment is larger than the sampling voltage of the second sampling point, and the distance deviation value of each sampling point on the second sub-curve segment decreases along with the increase of the sampling voltage.

41. The method of claim 39 or 40, wherein said receiving a plurality of sets of sample data for a first sample period of the first set of strings at a plurality of sample point pressures sent by the inverter and determining the operating profile of the first set of strings based on the plurality of sets of sample data for the first sample period comprises:

determining whether the first group of strings has a fault according to the distance deviation value from each sampling point on the first curve segment of the first sampling time period to the first straight line corresponding to the first curve segment of the first sampling time period, including:

42. The method of claim 41, wherein the N sampling periods comprise a second sampling period, and wherein a duration of an interval between the second sampling period and the first sampling period is greater than a preset interval duration threshold.

43. The method of claim 41, wherein the N sampling periods comprise N-1 third sampling periods;

receiving a plurality of groups of sampling data of the first sampling time period of the first group of strings under a plurality of sampling voltages, and determining a working characteristic curve of the first sampling time period based on the plurality of groups of sampling data of the first sampling time period, wherein the working characteristic curve of the first sampling time period comprises a first curve segment of the first sampling time period, and the first curve segment of the first sampling time period is a working characteristic curve obtained by sampling in the first sampling voltage interval;

44. The method is characterized by being applied to a power supply system, wherein the power supply system comprises a sampling device, an inverter and a first group string connected with the inverter;

the method comprises the following steps:

receiving multiple groups of sampling data of a first sampling time period of the first group of sampling voltages in series sent by the sampling device, and determining a working characteristic curve of the first sampling time period based on the multiple groups of sampling data of the first sampling time period, wherein the working characteristic curve of the first sampling time period comprises multiple curve segments of the first sampling time period, and each curve segment of the first sampling time period is a working characteristic curve obtained by sampling in each sampling voltage interval;

45. The method of claim 44, wherein the plurality of curve segments include a first curve segment, a second curve segment and a third curve segment, wherein the first curve segment is a working characteristic curve sampled in a first sampling voltage interval, the second curve segment is a working characteristic curve sampled in a second sampling voltage interval, the third curve segment is a working characteristic curve sampled in a third sampling voltage interval, the second sampling voltage interval is adjacent to the first sampling voltage interval and the third sampling voltage interval, and the sampling voltage of each sampling point in the second sampling voltage interval is greater than the sampling voltage of each sampling point in the first sampling voltage interval and less than the sampling voltage of each sampling point in the third sampling voltage interval;

the determining whether the first group of strings is faulty according to the first derivative characteristic values of the curve segments of the first sampling time period includes:

determining whether the first set of strings is faulty based on a sixth difference between the first derivative eigenvalue of the first curve segment and the first derivative eigenvalue of the second curve segment, and a seventh difference between the first derivative eigenvalue of the second curve segment and the first derivative eigenvalue of the third curve segment.

46. The method of claim 45, wherein said determining whether the first set of strings is faulty based on a sixth difference between the first derivative characteristic of the first curve segment and the first derivative characteristic of the second curve segment, and a seventh difference between the first derivative characteristic of the second curve segment and the first derivative characteristic of the third curve segment comprises:

determining that the first group of strings is faulty when a ratio between the sixth difference and the seventh difference is greater than a preset ratio threshold.

47. The method of claim 45, wherein said determining whether the first set of strings is faulty based on a sixth difference between the first derivative characteristic of the first curve segment and the first derivative characteristic of the second curve segment, and a seventh difference between the first derivative characteristic of the second curve segment and the first derivative characteristic of the third curve segment comprises:

and when the sixth difference is greater than a seventh preset difference threshold and the seventh difference is less than an eighth preset difference threshold, determining that the first group of strings has a fault.

48. The method according to any one of claims 44-47, wherein said determining a first derivative eigenvalue for each curve segment comprises:

and determining a first derivative value of each sampling point on each curve segment, and determining the average value of the first derivative values of all the sampling points on each curve segment as a first derivative characteristic value of each curve segment.

49. The method of any one of claims 44-48, wherein said receiving a plurality of sets of sample data sent by said inverter for a first sample period of said first set of strings at a plurality of sample voltages and determining an operating profile for said first sample period based on said plurality of sets of sample data for said first sample period comprises:

the determining the first derivative characteristic value of each curve segment of the first sampling time period and determining whether the first group of strings has a fault according to the first derivative characteristic value of each curve segment of the first sampling time period includes:

50. The method of claim 49, wherein the N sampling periods comprise a second sampling period, and wherein a duration of an interval between the second sampling period and the first sampling period is greater than a preset interval duration threshold.

51. The method of claim 49, wherein said N sampling periods comprise N-1 third sampling periods;

receiving a plurality of sets of sampling data of the first sampling time period of the first set of strings under a plurality of sampling voltages, and determining an operating characteristic curve of the first sampling time period based on the plurality of sets of sampling data of the first sampling time period, wherein the operating characteristic curve of the first sampling time period comprises a plurality of curve segments of the first sampling time period;

52. The method is characterized by being applied to a power supply system, wherein the power supply system comprises a sampling device, an inverter and a first group string connected with the inverter;

the method comprises the following steps:

53. The method of claim 52, wherein said determining whether the first set of strings is faulty according to the second derivative value of the third sample point on the operating characteristic curve of the first sample period comprises:

and when the second derivative value of the third sampling point is 0, determining that the first group of strings has faults.

54. The method of claim 52 or 53, wherein the receiving of the plurality of sets of sample data of the first set of sample periods of the first series at the plurality of sample voltages sent by the inverter and the determining of the operating characteristic of the first sample period based on the plurality of sets of sample data of the first sample period comprises:

determining whether the first group of strings has a fault according to a second derivative value of a third sampling point on the working characteristic curve of the first sampling time period comprises:

55. The method of claim 54, wherein the N sampling periods comprise a second sampling period, and wherein a duration of an interval between the second sampling period and the first sampling period is greater than a preset interval duration threshold.

56. The method of claim 54, wherein the N sampling periods comprise N-1 third sampling periods;