CN107561347B - Method and system for evaluating severity of voltage sag - Google Patents
Method and system for evaluating severity of voltage sag Download PDFInfo
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Abstract
The invention relates to a method and a system for evaluating the severity of voltage sag.A weight function of the influence degree of the voltage sag performance is calculated according to a voltage sag tolerance curve, and the influence degree of the voltage sag is calculated according to the weight function; wherein the voltage sag influence magnitude represents a severity of a voltage sag event; respectively calculating time parameters of corresponding sampling points according to the measured voltage values of the sampling points in the voltage sag process, and respectively substituting the time parameters of the sampling points into the voltage sag influence degree to obtain single voltage sag performance parameters of the corresponding sampling points; the maximum of the voltage sag performance parameters is set as the single voltage sag severity of the voltage sag event.
Description
Technical Field
The invention relates to the technical field of power quality analysis, in particular to a method and a system for evaluating the severity of voltage sag.
Background
Voltage sag is a core problem facing the field of power quality. Voltage sag has a great influence on industrial users, and the harm caused by the voltage sag and the huge economic loss caused by the voltage sag are important problems faced by many users. Many sophisticated electronic and power electronic controllers based on computer, microprocessor controllers are very sensitive to voltage sags.
The sag score is a commonly used index in the detection of the severity of voltage sag, and the index is actually applied by a power supply department. In addition, a sag event severity Index, an energy Index, an Index of a System Average RMS Variation Frequency Index (sarf), an equipotential chart, a statistical table, and the like are also commonly used indexes for detecting the severity of a sag. However, these indicators are generally less accurate when detecting the severity of a voltage sag.
Disclosure of Invention
In view of the above, it is necessary to provide a method and a system for evaluating the severity of voltage sag, aiming at the problem of low detection accuracy.
A method for evaluating the severity of voltage sag comprises the following steps:
calculating a weight function of the influence degree of the voltage sag performance according to the voltage sag tolerance curve, and calculating the influence degree of the voltage sag according to the weight function; wherein the voltage sag influence magnitude represents a severity of a voltage sag event;
respectively calculating time parameters of corresponding sampling points according to the measured voltage values of the sampling points in the voltage sag process, and respectively substituting the time parameters of the sampling points into the voltage sag influence degree to obtain single voltage sag performance parameters of the corresponding sampling points;
the maximum of the voltage sag performance parameters is set as the single voltage sag severity of the voltage sag event.
A voltage sag severity evaluation system comprising:
the first calculation module is used for calculating a weight function of the influence degree of the voltage sag performance according to the voltage sag tolerance curve and calculating the influence degree of the voltage sag according to the weight function; wherein the voltage sag influence magnitude represents a severity of a voltage sag event;
the second calculation module is used for respectively calculating the time parameters of the corresponding sampling points according to the measured voltage values of the sampling points in the voltage sag process, and substituting the time parameters of the sampling points into the voltage sag influence degree to obtain single voltage sag performance parameters of the corresponding sampling points;
and the setting module is used for setting the maximum one of the voltage sag performance parameters as the single voltage sag severity of the voltage sag event.
According to the method and the system for evaluating the severity of the voltage sag, the severity of the voltage sag is calculated by calculating the weight function of the influence of the voltage sag performance, the single voltage sag performance parameter is calculated according to the measured voltage value of each sampling point in the voltage sag process, the maximum voltage sag performance parameter is set as the severity of the single voltage sag of the voltage sag event, the method and the system can be used for accurately evaluating the voltage sag, the problems of over-evaluation and under-evaluation in the existing indexes are effectively avoided, and the detection accuracy of the severity of the voltage sag is improved.
Drawings
FIG. 1 is a flow diagram of a method for evaluating the severity of a voltage sag, according to one embodiment;
FIG. 2 is a voltage sag generalized tolerance curve for one embodiment;
FIG. 3(a) is a key node schematic for single/two phase voltage sag determination according to one embodiment;
FIG. 3(b) is a key node schematic for three-phase voltage sag determination of an embodiment;
FIG. 4(a) is a graph illustrating a weight function of the duration influence of a single/two phase voltage sag according to one embodiment;
FIG. 4(b) is a graph illustrating a weight function of the duration influence of a three-phase voltage sag according to one embodiment;
FIG. 5(a) is a graph illustrating a weight function of the magnitude-dependent magnitude of a single-phase/two-phase voltage sag according to one embodiment;
FIG. 5(b) is a graph illustrating a weight function of the magnitude-dependent magnitude of a three-phase voltage sag, according to one embodiment;
FIG. 6(a) is a schematic diagram of an actual instantaneous voltage sag waveform for a voltage sag event according to one embodiment;
FIG. 6(b) is a diagram illustrating an actual RMS waveform of a voltage sag at a voltage sag event according to an embodiment;
FIG. 7 is a block diagram of a voltage sag severity evaluation system, according to an embodiment.
Detailed Description
The technical solution of the present invention will be explained below with reference to the accompanying drawings.
Detailed inferential analysis methods and exemplary analysis examples are disclosed below. However, the specific reasoning and analysis process details disclosed herein are for purposes of describing example analysis examples only.
It should be understood, however, that the intention is not to limit the invention to the particular exemplary embodiments disclosed, but to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure. Like reference numerals refer to like elements throughout the description of the figures.
As shown in fig. 1, the present invention provides a method for evaluating the severity of a voltage sag, which comprises the following steps:
s1, calculating a weight function of the influence degree of the voltage sag performance according to the voltage sag tolerance curve, and calculating the influence degree of the voltage sag according to the weight function; wherein the voltage sag influence magnitude represents a severity of a voltage sag event;
in combination with the voltage sag tolerance curve shown in fig. 2, the characteristics of the influence of the duration of the voltage sag and the amplitude of the voltage sag on the severity of the voltage sag event are considered, and the longer the duration is, the lower the amplitude is, the more serious the voltage sag is, the larger the corresponding influence value is, specifically: in fig. 2, the voltage sag event occurring in the non-fault region does not cause the device fault, and the influence value of the voltage sag duration and the voltage sag amplitude in this region should change slowly and approach 0; the voltage sag event in the fault area can cause equipment fault, so that the influence value of the voltage sag duration and the voltage sag amplitude in the area is relatively smooth and is close to 1; in the voltage sag event in the uncertain region, the duration of the voltage sag or the change of the amplitude of the voltage sag can generate great influence on equipment, the influence value of the duration of the voltage sag or the change of the amplitude of the voltage sag is changed quickly, and the duration and the amplitude have the characteristic of gradual change and quick change in the middle of two ends on the severity influence response of the voltage sag event. Thus, in one embodiment, the following function may be employed as a weighted function of duration and magnitude:
wherein K, a, b are control parameters, where K is 1; x is an independent variable and corresponds to the sag duration T or the sag amplitude U in the invention; y is a dependent variable, and the weight function TD (T), TD corresponding to the influence degree of the sag duration T in the invention3(T) or the weight function MD (U), MD of the influence degree of the sag amplitude U3(U). The weight function adopted by the embodiment can simulate the influence characteristics of the duration and the amplitude on the voltage sag event under the real condition to a greater extent, so that the subsequent calculation accuracy is improved.
In one embodiment, a trip point of the voltage sag tolerance curve may be obtained; calculating control parameters of the weight function according to the maximum value and the minimum value in the jumping points; and determining the weight function according to the control parameter.
The single-phase voltage sag event and the two-phase voltage sag event can be considered as a class of voltage sag events, and both asymmetric sag events are adopted, so that the C4.110 working group provides a unified standard sag tolerance curve for the two asymmetric single-phase/two-phase sag events, while a SEMI F47 curve and an ITIC curve in the existing standard tolerance curve do not provide corresponding tolerance curves for different sag types, and therefore the SEMI F47 curve and the ITIC curve are considered to be applicable to all sag types in the invention; on the other hand, due to the difference between different standard tolerance curves, in order to comprehensively consider the different standard tolerance curves, the invention integrates three tolerance curves, namely the SEMI F47 curve, the ITIC curve and the standard curve given by the C4.110 working group, so that the selection of the key node can be more accurate. As shown in fig. 3(a), the withstand curve jumps at durations of 0.02s, 0.2s, and 0.5s, and jumps at sag amplitudes of 0.4, 0.5, 0.7, and 0.8. The jump of the endurance curve indicates a sudden change of the state of the device, i.e. the duration of the voltage sag or a change in the magnitude of the voltage sag by a very small value causes a sudden change of the state of the device. In each duration zone, when the sag amplitude is determined, the duration has almost no influence on the state of the equipment, and in each sag amplitude zone, when the duration is determined, the sag amplitude has almost no influence on the state of the equipment, so that the jump points are the key for determining the distribution of the influence degree function, two extreme values are respectively selected, the key points of the voltage sag duration are determined to be 0.02s and 0.5s, and the key points of the voltage sag amplitude are determined to be 0.4 and 0.8.
For the three-phase sag, according to the existing standard tolerance curve SEMI F47 curve, ITIC curve and the standard sag tolerance curve for the symmetrical three-phase sag given by the C4.110 working group, as shown in fig. 3(b), considering that the severity of the three-phase sag should be higher than that of the single phase under the same sag condition, the three curves are combined to obtain a most severe voltage sag tolerance curve, i.e., the upper envelope curve of fig. 3(b), for which the tolerance curve jumps at the time durations of 0.02s and 0.2s, and jumps at the time durations of 0.7 and 0.8, and two extreme values are respectively selected, so that the key points of the duration are determined to be 0.02s and 0.2s, and the key points of the sag amplitude are determined to be 0.7 and 0.8.
For single/two-phase sag, regarding the weight function of the influence degree corresponding to the sag duration T, it is considered that the lower part of the curve is a fault area, the influence value of which is close to 1, and the upper part of the curve is a non-fault area, the influence value of which is close to 0, a confidence interval of 95% can be selected, so that the influence value corresponding to the duration 0.02s is 0.05, the influence value corresponding to the duration 0.5 is 0.95, and according to the duration normalized interval mapping, the normalized mapping value of 0.02s is 0, 0.5s is mapped to 0.375, so that the weight function of the influence degree corresponding to the duration T crosses the points (0,0.05) and (0.375,0.95), and the expression is:
in the same way, the weight function expression of the influence degree corresponding to the three-phase sag duration time T can be obtained as follows:
fig. 4(a) shows a voltage sag duration influence degree change curve of a single-phase/two-phase voltage sag, and fig. 4(b) shows a voltage sag duration influence degree change curve of a three-phase voltage sag.
Regarding the single-phase/two-phase sag, regarding the weight function of the influence degree corresponding to the sag amplitude U, it is considered that the lower part of the curve is a fault area, the influence degree value is close to 1, and the upper part of the curve is a non-fault area, the influence degree value is close to 0, a 95% confidence interval is selected, the influence degree value when the amplitude is 0.4 is 0.95, and the influence degree value when the amplitude is 0.8 is 0.15, so that the weight function of the influence degree corresponding to the sag amplitude U crosses the point (0.4,0.95) and (0.8,0.15), and the expression is:
in the same way, the weight function expression of the influence degree corresponding to the sag value U of the three-phase sag is obtained as follows:
fig. 5(a) shows a voltage sag amplitude variation curve of a single-phase/two-phase voltage sag, and fig. 5(b) shows a voltage sag amplitude variation curve of a three-phase voltage sag.
Further, the voltage amplitude U and the duration T in the single-phase/two-phase sag event sag process can be respectively calculated, and then the sag severity represented by the amplitude and the duration is quantized and represented by a normalized modulus value obtained by combining the two values, wherein the larger the modulus value is, the more severe the sag is, and the calculation formula is as follows:
wherein, MTD (U, T) is the voltage sag influence degree of the single-phase voltage sag event or the two-phase voltage sag event, md (U) is the voltage sag influence degree corresponding to the voltage sag amplitude of the single-phase voltage sag event or the two-phase voltage sag event, and td (T) is the voltage sag influence degree corresponding to the voltage sag duration of the single-phase voltage sag event or the two-phase voltage sag event.
Similarly, the corresponding influence degree calculation formula in the three-phase voltage sag process is as follows:
in the formula, MTD3(U, T) is the voltage sag influence degree of the three-phase voltage sag event, MD3(U) is the voltage sag influence degree corresponding to the voltage sag amplitude of the three-phase voltage sag event, TD3And (T) is the voltage sag influence degree corresponding to the voltage sag duration of the three-phase voltage sag event.
S2, respectively calculating time parameters of corresponding sampling points according to the measured voltage values of the sampling points in the voltage sag process, and respectively substituting the time parameters of the sampling points into the voltage sag influence degree to obtain single voltage sag performance parameters of the corresponding sampling points;
this step allows the severity of a single event voltage sag to be assessed. Specifically, for a certain sag event, the voltage sag s is first described as a function of the voltage U and the time t:
u ═ s (t) or t ═ s-1(U)
Then combining the voltage waveform data measured by the sag to obtain any voltage amplitude U in the sag processcUsually, the voltage in the corresponding measured voltage sag waveform is UcAt two points in time tc1，tc2. Defining:
T(Uc)＝|tc1-tc2|(0.1≤Uc≤0.9)
in the formula of T (U)c) The voltage amplitude does not exceed U in the sag processcThe corresponding time. U shapecRepresenting the value of U at any time.
And finally, selecting a series of reasonable voltage thresholds, and taking the corresponding duration time sequence as a novel voltage sag description mode with multiple sag thresholds and durations.
In the invention, a multi-sag threshold value and duration sequence T (0.9), T (0.9-h) and T (0.9-2h) … … T (0.1) are used as a novel description method of voltage sag, and h is 0.1. For each of the above thresholds, respectively:
MTD(0.9,T(0.9)),MTD(0.9-h,T(0.9-h)),
MTD(0.9-2h,T(0.9-2h)),L,MTD(0.1,T(0.1))
and
MTD3(0.9,T(0.9)),MTD3(0.9-h,T(0.9-h)),
MTD3(0.9-2h,T(0.9-2h)),L,MTD3(0.1,T(0.1))
s3, setting the maximum one of the voltage sag performance parameters as the single voltage sag severity of the voltage sag event.
Aiming at the severity evaluation of a single sag event, the invention provides a voltage sag comprehensive influence degree index based on a multi-threshold description method, wherein the influence degree value of single-phase/two-phase sag is calculated as follows:
D＝max{MTD(0.9,T(0.9)),MTD(0.9-h,T(0.9-h)),
MTD(0.9-2h,T(0.9-2h))，L，MTD(0.1,T(0.1))}
the influence value of the three-phase sag is calculated as follows:
D3＝max{MTD3(0.9,T(0.9)),MTD3(0.9-h,T(0.9-h)),
MTD3(0.9-2h,T(0.9-2h))，L，MTD3(0.1,T(0.1))}
namely, the severity of the voltage sag is measured by selecting the maximum value by calculating the influence degree corresponding to each voltage threshold and the duration thereof in the sag process. The index considers the actual waveform characteristics and also considers the influence of duration and amplitude, and can more comprehensively and accurately depict the sag severity.
In addition, the method for evaluating the severity of voltage sag can also evaluate the severity of voltage sag of the node. Specifically, the severity of the total voltage sag of the nodes of the single node in the past voltage sag events can be respectively obtained; and taking the average value of the node total voltage sag severity of the single node in the voltage sag events as the node average voltage sag severity of the voltage sag events.
Since a single node may have multiple sag events, based on the integrated influence metric of voltage sag for a single event, in one embodiment, the following metric may be defined for the voltage sag severity evaluation of a single node:
the node total voltage sag severity of the r-th node is expressed as follows:
the node average voltage sag severity for the r-th node is expressed as follows:
in the formula NrRepresenting the total number of dips, M, occurring at the r-th node in the systemrRepresents NrThe number of temporary drops of the medium and three phases; dlThe voltage sag influence degree of the first single-phase/two-phase sag event is represented and can be calculated by D in the voltage sag severity degree of a single event; d3,lThe influence degree of the I th three-phase sag event can be represented by D in the voltage sag severity degree of a single event3And (4) calculating.
In addition, the voltage sag severity detection method of the present invention can also evaluate the user-level and system-level voltage sag severity. Specifically, the severity of the total voltage sag of the nodes of each node can be obtained respectively; calculating the user average voltage sag severity of the voltage sag event according to the node total voltage sag severity of each node and the number of target nodes; the target node is a node where a voltage sag event occurs; and calculating the system average voltage sag severity of the voltage sag event according to the node total voltage sag severity of each node and the node total number.
Typically, a system includes multiple nodes, and thus, for a system with m nodes, the severity of voltage sag evaluation may define the following:
average voltage sag severity of users:
system average voltage sag severity:
wherein ASDC is the average voltage sag severity of the user, ASDS is the average voltage sag severity of the system, SDrThe severity of the total voltage sag at the node of the r-th node, NrTotal number of voltage sag events, M, for the r-th noderTotal number of three-phase voltage sag events occurring for the r-th node, DlThe magnitude of the voltage sag effect of the first single-phase voltage sag event or two-phase voltage sag event, D3,lThe magnitude of the voltage sag effect of the first three-phase voltage sag event, NCThe number of target users for each node in the system to generate the sag event, namely, the number of all users generating sag at each node, NSM is the total number of the nodes in the system.
The technical effects of the present invention will be described below with reference to a specific embodiment.
The actual waveform of a certain voltage sag event occurring in the power quality monitoring system of a certain city power grid in 2012, 2, month, 29, 15:59:39 at a certain time is shown in fig. 6, and the comprehensive influence index of the voltage sag event is calculated by taking the voltage sag event as an example.
Fig. 6 shows a sag event, which is a two-phase sag, and the calculation formula of the influence of the two-phase sag is selected, in the voltage sag multi-threshold description method, for voltage thresholds 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, the voltage sag durations T (0.9), T (0.8), T (0.7, … …, T (0.1) of each threshold mapping were calculated as follows: 0.0633s, 0.0448s, 0.0204s, 0s, calculating the influence value corresponding to the sag threshold value and the duration time sequence, and the result is as follows: 0.0711, 0.0645, 0.0971, 0, based on the above calculation results, it can be finally obtained that the single voltage sag severity of the voltage sag severity evaluation method considering the sag type and multi-threshold description corresponding to the sag event is 0.0971.
In the conventional voltage sag description method, according to fig. 6, the obtained voltage sag amplitude is 0.6989, the voltage sag duration is 0.0600s, and the calculated single voltage sag severity is 0.1111.
Fig. 6 is a typical non-rectangular waveform, however, for a sag event of a rectangular wave type with an amplitude of 0.6989 and a duration of 0.0600s, the single voltage sag severity degree obtained by using the conventional description method and the multi-threshold description method is 0.1111, which is the same as the influence value obtained by using the conventional description method to calculate the sag event in fig. 6, and is greater than the single voltage sag severity degree 0.0971 calculated by using the multi-threshold description method of the present invention, so that the sag event of the rectangular wave type is more severe than the non-rectangular wave voltage sag event in fig. 6, which is more realistic than the sag event of the rectangular wave type calculated by using the multi-threshold description method. Therefore, the single voltage sag severity index calculated by the multi-threshold description method can avoid over-evaluation of non-rectangular sag events, and the evaluation result is more reasonable than that of the traditional description method.
The comprehensive evaluation method for the severity of the voltage sag, which considers sag types and multi-threshold description, has the main advantages that voltage sag tolerance curves under different sag types are considered, and the severity of the voltage sag under single-phase/two-phase and three-phase different sag types can be more accurately reflected; the traditional voltage sag description mode is replaced by a description method of multiple sag thresholds and duration time sequences, and the actual waveform characteristics reflecting the voltage sag can be more accurately described; the multi-threshold description mode is combined with the weight function, comprehensive influence indexes suitable for single event, node and system evaluation are respectively provided, the method can be used for accurate evaluation of voltage sag, and the problems of over-evaluation and under-evaluation in the existing indexes are effectively avoided.
According to the comprehensive evaluation method for the severity of the voltage sag, which considers the sag type and the multi-threshold description, the severity of a single event, a node and a system voltage sag event can be conveniently and effectively evaluated accurately.
As shown in fig. 7, the present invention further provides a system for evaluating the severity of voltage sag, which may include:
the first calculating module 10 is configured to calculate a weight function of a voltage sag influence degree according to a voltage sag tolerance curve, and calculate a voltage sag influence degree according to the weight function; wherein the voltage sag influence magnitude represents a severity of a voltage sag event;
the second calculation module 20 is configured to calculate time parameters of corresponding sampling points according to actually measured voltage values of the sampling points in the voltage sag process, and substitute the time parameters of the sampling points into the voltage sag influence degree to obtain single voltage sag performance parameters of the corresponding sampling points;
a setting module 30, configured to set a maximum one of the voltage sag performance parameters as a single voltage sag severity of the voltage sag event.
The voltage sag severity evaluation system and the voltage sag severity evaluation method are in one-to-one correspondence, and technical features and beneficial effects described in the embodiment of the voltage sag severity evaluation method are all applicable to the embodiment of the voltage sag severity evaluation system, so that the state is declared.
The logic and/or steps represented in the flowcharts or otherwise described herein, e.g., an ordered listing of executable instructions that can be considered to implement logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.
It should be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A method for evaluating the severity of voltage sag is characterized by comprising the following steps:
obtaining a voltage sag tolerance curve according to a SEMIF47 curve, an ITIC curve and a standard sag tolerance curve for symmetrical three-phase voltage sag given by a C4.110 working group; calculating a weight function of the influence degree of the voltage sag performance according to the voltage sag tolerance curve, and calculating the influence degree of the voltage sag according to the weight function; respectively considering the characteristics of the influence of the voltage sag duration and the voltage sag amplitude on the severity of the voltage sag event by combining the voltage sag tolerance curve; wherein the voltage sag influence magnitude represents a severity of a voltage sag event; wherein, the step of calculating the voltage sag influence degree according to the weight function comprises the following steps:
for a three-phase voltage sag event, the voltage sag influence degree is calculated as follows:
in the formula, MTD3(U, T) is the voltage sag influence degree of the three-phase voltage sag event, MD3(U) is the voltage sag influence degree corresponding to the voltage sag amplitude of the three-phase voltage sag event, TD3(T) is the voltage sag influence degree corresponding to the voltage sag duration of the three-phase voltage sag event;
respectively calculating time parameters of corresponding sampling points according to the measured voltage values of the sampling points in the voltage sag process, and respectively substituting the time parameters of the sampling points into the voltage sag influence degree to obtain single voltage sag performance parameters of the corresponding sampling points;
setting the maximum one of the voltage sag performance parameters as the single voltage sag severity of the voltage sag event;
wherein, the step of calculating the voltage sag influence degree according to the weight function comprises the following steps:
the following function is used as a weight function of duration and amplitude:
wherein K, a and b are control parameters; x is an independent variable corresponding to the sag duration T or the sag amplitude U; y is a dependent variable corresponding to the weight function TD of the influence of the sag duration T3(T) or sag amplitude U influence degree weight function MD3(U)。
2. The method according to claim 1, wherein the step of calculating a weight function of the voltage sag performance influence degree according to the voltage sag tolerance curve comprises:
acquiring a trip point of the voltage sag tolerance curve;
calculating control parameters of the weight function according to the maximum value and the minimum value in the jumping points;
and determining the weight function according to the control parameter.
3. The method according to claim 1, wherein the step of calculating the voltage sag influence degree according to the weight function comprises:
for a single-phase voltage sag event or a two-phase voltage sag event, the voltage sag influence degree is calculated according to the following method:
wherein, MTD (U, T) is the voltage sag influence degree of the single-phase voltage sag event or the two-phase voltage sag event, md (U) is the voltage sag influence degree corresponding to the voltage sag amplitude of the single-phase voltage sag event or the two-phase voltage sag event, and td (T) is the voltage sag influence degree corresponding to the voltage sag duration of the single-phase voltage sag event or the two-phase voltage sag event.
4. The method according to claim 1, wherein for a sag event, a voltage sag s is first described as a function of voltage U and time t:
u ═ s (t) or t ═ s-1(U)
Then combining the voltage waveform data measured by the sag to obtain any voltage amplitude U in the sag processcUsually, the voltage in the corresponding measured voltage sag waveform is UcAt two points in time tc1，tc2(ii) a Defining:
T(Uc)＝|tc1-tc2|(0.1≤Uc≤0.9)
in the formula of T (U)c) The voltage amplitude does not exceed U in the sag processcA corresponding time; u shapecRepresents the value of U at any time;
and finally, selecting a series of reasonable voltage thresholds, and taking the corresponding duration time sequence as a novel voltage sag description mode with multiple sag thresholds and durations.
5. The method of claim 4, further comprising the steps of:
respectively acquiring the severity of node total voltage sag of a single node in the past voltage sag events;
and taking the average value of the node total voltage sag severity of the single node in the voltage sag events as the node average voltage sag severity of the voltage sag events.
6. The method according to claim 5, wherein the step of obtaining the total voltage sag severity of the nodes of the voltage sag events of the single node in the past comprises:
the severity of the node total voltage sag of a single node is calculated according to the following method:
in the formula, SDrThe severity of the total voltage sag at the node of the r-th node, NrTotal number of voltage sag events, M, for the r-th noderTotal number of three-phase voltage sag events occurring for the r-th node, DlThe magnitude of the voltage sag effect of the first single-phase voltage sag event or two-phase voltage sag event, D3,lThe voltage sag influence degree of the l-th three-phase voltage sag event.
7. The method of claim 1, further comprising the steps of:
respectively acquiring the severity of node total voltage sag of each node;
calculating the user average voltage sag severity of the voltage sag event according to the node total voltage sag severity of each node and the number of target nodes; the target node is a node where a voltage sag event occurs;
and calculating the system average voltage sag severity of the voltage sag event according to the node total voltage sag severity of each node and the node total number.
8. The method of claim 7, wherein the step of calculating the user average voltage sag severity of the voltage sag event based on the node total voltage sag severity of each node and the number of target nodes comprises:
calculating the user average voltage sag severity according to the following method:
wherein ASDC is average voltage sag severity of subscriber, SDrThe severity of the total voltage sag at the node of the r-th node, NrTotal number of voltage sag events, M, for the r-th noderTotal number of three-phase voltage sag events occurring for the r-th node, DlThe magnitude of the voltage sag effect of the first single-phase voltage sag event or two-phase voltage sag event, D3,lThe magnitude of the voltage sag effect of the first three-phase voltage sag event, NCM is the total number of nodes in the system.
9. The method of claim 7, wherein the step of calculating the system average voltage sag severity of the voltage sag event based on the total voltage sag severity of the nodes and the total number of nodes of each node comprises:
calculating the average voltage sag severity of the system according to the following method:
wherein ASDS is the system average voltage sag severity, SDrThe severity of the total voltage sag at the node of the r-th node, NrTotal number of voltage sag events, M, for the r-th noderTotal number of three-phase voltage sag events occurring for the r-th node, DlThe magnitude of the voltage sag effect of the first single-phase voltage sag event or two-phase voltage sag event, D3,lThe magnitude of the voltage sag effect of the first three-phase voltage sag event, NSM is the total number of the nodes in the system.
10. A system for evaluating the severity of a voltage sag, comprising:
the first calculation module is used for obtaining a voltage sag tolerance curve according to a SEMIF47 curve, an ITIC curve and a standard sag tolerance curve for symmetrical three-phase voltage sag given by a C4.110 working group; the weight function is used for calculating the influence degree of the voltage sag performance according to the voltage sag tolerance curve, and the influence degree of the voltage sag is calculated according to the weight function; respectively considering the characteristics of the influence of the voltage sag duration and the voltage sag amplitude on the severity of the voltage sag event by combining the voltage sag tolerance curve; wherein the voltage sag influence magnitude represents a severity of a voltage sag event; wherein, the step of calculating the voltage sag influence degree according to the weight function comprises the following steps:
for a three-phase voltage sag event, the voltage sag influence degree is calculated as follows:
in the formula, MTD3(U, T) is the voltage sag influence degree of the three-phase voltage sag event, MD3(U) is the voltage sag influence degree corresponding to the voltage sag amplitude of the three-phase voltage sag event, TD3(T) three-phase Voltage sag eventThe voltage sag influence degree corresponding to the voltage sag duration;
the second calculation module is used for respectively calculating the time parameters of the corresponding sampling points according to the measured voltage values of the sampling points in the voltage sag process, and substituting the time parameters of the sampling points into the voltage sag influence degree to obtain single voltage sag performance parameters of the corresponding sampling points;
the setting module is used for setting the maximum one of the voltage sag performance parameters as the single voltage sag severity of the voltage sag event;
wherein, the step of calculating the voltage sag influence degree according to the weight function comprises the following steps:
the following function is used as a weight function of duration and amplitude:
wherein K, a and b are control parameters; x is an independent variable corresponding to the sag duration T or the sag amplitude U; y is a dependent variable corresponding to the weight function TD of the influence of the sag duration T3(T) or sag amplitude U influence degree weight function MD3(U)。
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| CN109856505B (en) * | 2019-01-11 | 2022-04-01 | 广东电网有限责任公司广州供电局 | Immune time detection method for voltage sag |
| CN110196377B (en) * | 2019-04-18 | 2021-11-19 | 华南理工大学 | Power grid voltage sag rating method |
| CN110137947B (en) * | 2019-05-10 | 2023-06-16 | 华南理工大学 | Grid voltage sag severity assessment method based on ITIC curve |
| CN110687344B (en) * | 2019-10-24 | 2021-11-12 | 南京南瑞继保电气有限公司 | Single-phase voltage sag detection method and device, voltage restorer, equipment and medium |
| CN111506878B (en) * | 2020-04-08 | 2022-05-03 | 国网湖北省电力有限公司电力科学研究院 | Node number selection device and method based on sag system index random sample estimation |
| CN111722002B (en) * | 2020-06-29 | 2022-08-23 | 国网四川省电力公司电力科学研究院 | Novel voltage sag severity assessment method |
| CN112285454B (en) * | 2020-09-11 | 2023-05-23 | 国网天津市电力公司电力科学研究院 | Voltage sag severity assessment method based on improved energy index |
| CN112686549B (en) * | 2020-12-31 | 2024-06-14 | 华南理工大学 | Node voltage sag severity assessment method, device, equipment and storage medium |
| CN112881824A (en) * | 2021-01-08 | 2021-06-01 | 国网安徽省电力有限公司电力科学研究院 | Method and device for evaluating influence of voltage sag of medium-voltage system on computer equipment |
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