CN113363951B - Direct current residual current protector, protection method and direct current power supply system - Google Patents
Direct current residual current protector, protection method and direct current power supply system Download PDFInfo
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- CN113363951B CN113363951B CN202110558189.6A CN202110558189A CN113363951B CN 113363951 B CN113363951 B CN 113363951B CN 202110558189 A CN202110558189 A CN 202110558189A CN 113363951 B CN113363951 B CN 113363951B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
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Abstract
The application relates to a direct current residual current protector, a protection method and a direct current power supply system. The control device obtains alternating current leakage current in the direct current line according to the residual current detected by the current sensor, obtains a compensation power supply value according to the alternating current leakage current, and controls the alternating current counteracting device to generate alternating current according to the compensation power supply value so as to counteract the alternating current leakage current in the direct current line, so that the direct current residual current can be detected by the current sensor, and the interference of the alternating current leakage current on the RCD is effectively avoided.
Description
Technical Field
The application relates to the technical field of power supply equipment, in particular to a direct current residual current protector, a protection method and a direct current power supply system.
Background
With the dc conversion of the equipment in the civil scene, the advantage of low-voltage dc power supply is revealed, and thus the dc power supply system of the civil scene is gradually formed. The application of civil scenes means that electric shock protection measures are added to ensure the safety of human bodies, and direct current residual current protection (Residual Current Operated Protective Devices, RCD) is one of the crucial measures, when electric shock occurs to the human bodies, the system can generate direct current residual current, and the RCD just uses the direct current residual current to protect the safety of the human bodies.
However, in actual operation, the dc power supply system also has an ac leakage current, which adversely affects the normal operation of the RCD. How to avoid the interference of the alternating current leakage current to the RCD is a problem to be solved.
Disclosure of Invention
Based on the above, it is necessary to provide a dc residual current protector, a protection method and a dc power supply system for solving the problem that the ac leakage current in the dc power supply system adversely affects the normal operation of the RCD, so as to achieve the effect of effectively avoiding the interference of the ac leakage current on the RCD.
The direct-current residual current protector comprises a current sensor, an alternating-current counteracting device and a control device, wherein the current sensor and the alternating-current counteracting device are arranged on a direct-current circuit of a direct-current power supply system, and the control device is connected with the current sensor and the alternating-current counteracting device;
the control device is used for obtaining alternating current leakage current in the direct current circuit according to residual current detected by the current sensor, obtaining a compensation power supply value according to the alternating current leakage current, and controlling the alternating current counteracting device to generate alternating current according to the compensation power supply value so as to counteract the alternating current leakage current in the direct current circuit.
In one embodiment, the control device calculates a compensation power supply value by PI (Proportional Integral, proportional and integral adjustment) based on the ac leakage current.
In one embodiment, the control device uses the ac leakage current as the controlled quantity of the PI control loop, and the PI control loop targets to control the ac component in the measurement winding of the current sensor to be 0, so as to perform PI calculation and output the compensation power supply value.
In one embodiment, the control device performs fast fourier transform on the residual current measured by the current sensor to obtain an ac leakage current.
In one embodiment, the control device filters the residual current measured by the current sensor to obtain an ac leakage current.
In one embodiment, the ac cancellation means comprises a compensation winding and a compensation power supply, the compensation power supply connecting the compensation winding and the control means.
In one embodiment, the dc residual current protector further includes an executing device connected to the control device, where the executing device is disposed in the dc power supply system; the control device is also used for disconnecting the power supply of the direct current power supply system through the execution device when the direct current residual current detected by the current sensor is larger than a preset threshold value.
A method of dc residual current protection comprising:
acquiring residual current detected by a current sensor; the current sensor is arranged on a direct current circuit of the direct current power supply system;
acquiring alternating current leakage current in the direct current line according to the residual current;
obtaining a compensation power supply value according to the alternating current leakage current, and controlling an alternating current counteracting device to generate alternating current according to the compensation power supply value so as to counteract the alternating current leakage current in the direct current circuit; the alternating current counteracting device is arranged on a direct current circuit of the direct current power supply system.
A direct current power supply system comprises the direct current residual current protector.
In one embodiment, the dc power supply system further includes a dc link that connects the power source and the powered device.
According to the direct current residual current protector, the protection method and the direct current power supply system, the control device obtains the alternating current leakage current in the direct current circuit according to the residual current detected by the current sensor, a compensation power supply value is obtained according to the alternating current leakage current, and the alternating current counteracting device is controlled to generate alternating current according to the compensation power supply value so as to counteract the alternating current leakage current in the direct current circuit, so that the direct current residual current can be detected by the current sensor, and the interference of the alternating current leakage current on the RCD is effectively avoided.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments or the conventional techniques of the present application, the drawings required for the descriptions of the embodiments or the conventional techniques will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort for those skilled in the art.
FIG. 1 is a block diagram of a DC residual current protector according to an embodiment;
FIG. 2 is a diagram of a PI control loop for controlling the AC component of the residual current measurement to be zero in one embodiment;
FIG. 3 is a schematic diagram of a current sensor and an AC offset device according to an embodiment;
FIG. 4 is a flow chart of a method for protecting DC residual current in an embodiment;
fig. 5 is a schematic diagram of an application scenario of a dc residual current protector in an embodiment.
Detailed Description
The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that the terms first, second, etc. as used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another element. For example, a first resistance may be referred to as a second resistance, and similarly, a second resistance may be referred to as a first resistance, without departing from the scope of the application. Both the first resistor and the second resistor are resistors, but they are not the same resistor.
It is to be understood that in the following embodiments, "connected" is understood to mean "electrically connected", "communicatively connected", etc., if the connected circuits, modules, units, etc., have electrical or data transfer between them.
As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," and/or the like, specify the presence of stated features, integers, steps, operations, elements, components, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof. Also, the term "and/or" as used in this specification includes any and all combinations of the associated listed items.
In one embodiment, a dc residual current protector is provided, which is suitable for solving the problem of inaccurate action caused by ac leakage current of a dc RCD in a domestic low-voltage dc power supply system. As shown in fig. 1, the dc residual current protector includes a current sensor 110, an ac cancellation device 120, and a control device 130, wherein the current sensor 110 and the ac cancellation device 120 are disposed on a dc line of a dc power supply system, and the control device 130 is connected to the current sensor 110 and the ac cancellation device 120. The control device 130 is configured to obtain an ac leakage current in the dc line according to the residual current detected by the current sensor 110, obtain a compensation power value according to the ac leakage current, and control the ac cancellation device 120 to generate an ac according to the compensation power value so as to cancel the ac leakage current in the dc line.
Specifically, the current sensor 110 may employ a current transformer, and employ a fluxgate principle to implement detection of a trace amount of direct current. The ac cancellation device 120 and the current sensor 110 are disposed on the dc link, and the ac cancellation device 120 generates ac to cancel the ac leakage current in the dc link, so that the current sensor 110 can detect the dc residual current without being affected by the ac leakage current.
The control device 130 may be an MCU (Micro Control Unit ), a CPU (Central Processing Unit, central processing unit), or the like. The control device 130 may not only obtain the ac leakage current in the dc line, but also convert or filter the residual current after detecting the residual current including the ac component by the current sensor 110, extract the ac component to obtain an ac measurement value, and then inject a current having the same magnitude and opposite direction as the ac measurement value into the ac cancellation device 120, thereby canceling the ac leakage current in the dc line, and the dc residual current is detected by the current sensor 110.
In the above dc residual current protector, the control device 130 obtains the ac leakage current in the dc line according to the residual current detected by the current sensor 110, obtains the compensation power value according to the ac leakage current, and controls the ac cancellation device 120 to generate ac according to the compensation power value, so as to cancel the ac leakage current in the dc line, thereby detecting the dc residual current by the current sensor 110 and effectively avoiding the interference of the ac leakage current to the RCD.
In one embodiment, control device 130 performs a fast fourier transform on the residual current measured by the current sensor to obtain an ac leakage current. The residual current measured by the current sensor 110 is subjected to a fast fourier transform (Fast Fourier Transformer, FFT), and then an ac part of the main frequency band thereof is acquired, resulting in an ac leakage current.
In another embodiment, the control device 130 filters the residual current measured by the current sensor to obtain the ac leakage current. Specifically, after the residual current is measured by the current sensor 110, the ac component therein may be directly separated by a filter, thereby obtaining an ac leakage current.
In one embodiment, control device 130 performs PI calculations based on the ac leakage current to obtain the compensated power supply value. The PI regulation is a linear control, it forms the control deviation according to the given value and actual output value, the proportion and integral of the deviation form the control quantity through the linear combination, control the controlled object, the regulation control is accurate and reliable. In this embodiment, the control device 130 uses the ac leakage current as the controlled variable of the PI control loop, and the PI control loop targets to control the ac component in the measurement winding of the current sensor 110 to be 0, so as to perform PI calculation and output the compensation power supply value.
Specifically, as shown in fig. 2, an ac component in the residual current is obtained by using an FFT or a filter as a controlled quantity of the PI control loop; the PI control loop targets that the ac component in the measurement winding of the current sensor 110 is controlled to be 0, the feedback quantity is the ac component value, and the PI is calculated to obtain the compensation power value, so that the ac component generated by the ac cancellation device 120 can be cancelled with the ac leakage current.
The particular configuration of the ac cancellation device 120 is also not exclusive, and in one embodiment, the ac cancellation device 120 includes a compensation winding and a compensation power source that is coupled to the compensation winding and the control device 130.
Specifically, as shown in fig. 3, the compensation winding may be disposed on the same iron core as the measurement winding of the current sensor 110, after the residual current is detected by the measurement winding of the current sensor 110, when PI calculation is performed by the control device 130, the ac residual current in the residual current is obtained by first using the FFT or the filter as a given value (i.e., a controlled quantity), the actual output value (i.e., a feedback quantity) is an ac component output by the compensation power supply on the compensation winding, the control loop targets to control the ac component in the measurement winding of the current sensor 110 to be 0, specifically, the compensation power supply value is output by PI calculation, and a current equal to the ac measurement value in size and opposite in direction is injected on the compensation winding by the compensation power supply, so that the ac component has a cancellation effect.
In another embodiment, the ac cancellation device includes a common-mode magnetic core, a common-mode filter inductor, and an auxiliary winding, where the common-mode filter inductor and the auxiliary winding are disposed on the common-mode magnetic core, and the common-mode filter inductor is connected in series to the dc line, and the auxiliary winding is connected to the control device.
In order to avoid the influence of the ac leakage current on the detection of the dc residual current in the dc power supply system, it is also conceivable to series a common mode filter in the dc line to suppress the ac leakage current. However, when the dc residual current occurs, the common mode filter may be affected, and the common mode filter needs to have a larger dc residual current bearing capacity, and meanwhile, the suppression effect of the ac leakage current is also maintained. Therefore, in this embodiment, the ac cancellation device 120 adopts a design of adding an auxiliary winding to the common-mode magnetic core on the basis of the common-mode filter, and the current of the auxiliary winding is obtained by PI calculation and compensation by the control device 130.
Specifically, the ac leakage current is related to the switching frequency of the power converter in the dc power supply system, and by utilizing this characteristic, the residual current I that can be detected by the current sensor 110 RC Analysis to calculate the component I in which the switching frequency is dependent S According to I S Generates a compensation current I C . By continuously according to the residual current I RC And I S Regulating compensation current I C Up to residual current I RC Middle I S Minimum.
In one embodiment, the dc residual current protector further includes a signal amplifier, and the control device 130 is connected to the current sensor 110 through the signal amplifier. The signal detected by the current sensor 110 is amplified by the signal amplifier and then is transmitted to the control device 130, so that the control device 130 can conveniently perform signal analysis.
In addition, in one embodiment, the dc residual current protector further includes an executing device connected to the control device 130, where the executing device is disposed in the dc power supply system; the control device 130 is further configured to disconnect the power supply of the dc power supply system by the execution device when the dc residual current detected by the current sensor is greater than a preset threshold.
The value of the preset threshold is not unique, and can be set according to actual requirements. Specifically, the executing device may adopt a breaker, and when the direct current residual current is greater than a preset threshold value, the control device 130 controls the breaker to be opened, so as to trigger protection to open the power supply, thereby ensuring personal safety.
In one embodiment, as shown in fig. 4, there is further provided a dc residual current protection method, including:
step S110: and acquiring the residual current detected by the current sensor. The current sensor is arranged on a direct current circuit of the direct current power supply system. The current sensor can adopt a current transformer and adopts a fluxgate principle to realize the detection of micro direct current.
Step S120: and acquiring the alternating current leakage current in the direct current line according to the residual current. Specifically, the residual current measured by the current sensor may be subjected to fast fourier transform to obtain an ac leakage current. In addition, the residual current measured by the current sensor may be filtered to obtain the ac leakage current.
Step S130: and obtaining a compensation power supply value according to the alternating current leakage current, and controlling the alternating current counteracting device to generate alternating current according to the compensation power supply value so as to counteract the alternating current leakage current in the direct current line. The alternating current counteracting device is arranged on a direct current circuit of the direct current power supply system.
Specifically, the compensation power supply value may be obtained by PI calculation based on the ac leakage current. And taking the alternating current leakage current as the controlled quantity of the PI control loop, and performing PI calculation to output a compensation power supply value by taking the PI control loop as a control current sensor and controlling the alternating current component in a measuring winding to be 0. The specific structure of the ac cancellation device is not exclusive, and the ac cancellation device may be a structure including a compensation winding and a compensation power supply, or a structure including a common-mode magnetic core, a common-mode filter inductance, and an auxiliary winding.
It should be noted that, the specific limitation of the dc residual current protection method may be referred to the limitation of the dc residual current protector, and will not be described herein.
According to the direct current residual current protection method, the alternating current leakage current in the direct current circuit is obtained according to the residual current detected by the current sensor, the compensation power supply value is obtained according to the alternating current leakage current, the alternating current counteracting device is controlled to generate alternating current according to the compensation power supply value so as to counteract the alternating current leakage current in the direct current circuit, and therefore the direct current residual current can be detected by the current sensor, and interference of the alternating current leakage current on the RCD is effectively avoided.
In one embodiment, a dc power supply system is further provided, including the dc residual current protector described above. Further, the direct current power supply system further comprises a direct current circuit, and the direct current circuit is connected with a power supply and electric equipment. And D.C. power output by the power supply is transmitted to the electric equipment through the D.C. circuit for supplying power. The direct-current residual current protector comprises a current sensor, an alternating-current counteracting device and a control device, wherein the current sensor and the alternating-current counteracting device are arranged on a direct-current circuit of a direct-current power supply system, and the control device is connected with the current sensor and the alternating-current counteracting device.
The current sensor may employ a current transformer. The control means may be an MCU, CPU, etc. The control device may perform conversion or filtering processing on the residual current after detecting the residual current containing the ac component by the current sensor, extract the ac component to obtain an ac measurement value, and then inject a current having the same magnitude and opposite direction as the ac measurement value into the ac counteracting device, thereby counteracting the ac leakage current in the dc line, and the subsequent detection by the current sensor is the dc residual current.
In one embodiment, the control device performs a fast fourier transform on the residual current measured by the current sensor to obtain an ac leakage current. And performing fast Fourier transform on the residual current measured by the current sensor, and then acquiring an alternating current part of a main frequency band to obtain alternating current leakage current.
In another embodiment, the control device filters the residual current measured by the current sensor to obtain the alternating leakage current. After the residual current is obtained by measuring the current sensor, the alternating current component in the residual current is directly separated by using a filter, so that alternating current leakage current is obtained.
In one embodiment, the control device performs PI calculation to obtain the compensation power supply value according to the ac leakage current. PI regulation forms control deviation according to a given value and an actual output value, forms control quantity by linear combination of proportion and integral of the deviation, controls a controlled object, and is accurate and reliable in regulation control. In this embodiment, the control device uses the ac leakage current as the controlled variable of the PI control loop, and the PI control loop targets to control the ac component in the measurement winding of the current sensor to be 0, so as to perform PI calculation and output the compensation power supply value.
Specifically, an alternating current component in the residual current is obtained by utilizing FFT or a filter and is used as a controlled quantity of a PI control loop; the PI control loop aims at controlling the alternating current component in the measuring winding of the current sensor to be 0, the feedback quantity is the alternating current component value, and the PI is calculated to obtain the compensation power supply value, so that the alternating current component generated by the alternating current counteracting device can be counteracted with the alternating current leakage current.
In one embodiment, the ac cancellation means comprises a compensation winding and a compensation power supply, the compensation power supply being connected to the compensation winding and the control means. The compensation winding and the measuring winding of the current sensor can be arranged on the same iron core, after the residual current is obtained through detection of the measuring winding of the current sensor, when PI calculation is carried out by the control device, firstly, the alternating current residual current in the residual current is obtained by utilizing FFT or a filter to serve as a given value (namely controlled quantity), the actual output value (namely feedback quantity) is an alternating current component output by the compensation power supply on the compensation winding, the control loop aims at controlling the alternating current component in the measuring winding of the current sensor to be 0, specifically, the compensation power supply value is output through PI calculation, and a current with the same size and opposite direction to the alternating current measured value is injected on the compensation winding through the compensation power supply, so that the alternating current component has a counteracting effect.
In another embodiment, the ac cancellation device includes a common-mode magnetic core, a common-mode filter inductor, and an auxiliary winding, where the common-mode filter inductor and the auxiliary winding are disposed on the common-mode magnetic core, and the common-mode filter inductor is connected in series to the dc line, and the auxiliary winding is connected to the control device. In this embodiment, the ac cancellation device is based on a common-mode filter, and a design of adding an auxiliary winding on a common-mode magnetic core is adopted, and the current of the auxiliary winding is obtained by PI calculation and compensation by the control device.
In one embodiment, the direct current residual current protector further comprises a signal amplifier, and the control device is connected with the current sensor through the signal amplifier.
In addition, in one embodiment, the direct current residual current protector further comprises an executing device connected with the control device, wherein the executing device is arranged on the direct current power supply system; the control device is also used for disconnecting the power supply of the direct current power supply system through the execution device when the direct current residual current detected by the current sensor is larger than a preset threshold value.
According to the direct current power supply system, the alternating current leakage current in the direct current circuit is obtained according to the residual current detected by the current sensor, the compensation power supply value is obtained according to the alternating current leakage current, and the alternating current counteracting device is controlled to generate alternating current according to the compensation power supply value so as to counteract the alternating current leakage current in the direct current circuit, so that the direct current residual current can be detected by the current sensor, and the interference of the alternating current leakage current on the RCD is effectively avoided.
In order to facilitate better the above-mentioned dc residual current protector and dc power supply system, a detailed explanation will be given below in connection with specific embodiments.
RCD is used as an important link of electric shock protection, and has wide application prospect in the scenes of electric automobile charging facilities (charging piles and charging stations), photovoltaic power generation, civil buildings, municipal road illumination, data center direct current power supply systems and the like. The civil dc power supply system is only in an initial test and demonstration stage, and the dc RCD product is not mature, but according to analysis, the ac leakage current in the dc system may have adverse effects on the normal operation of the dc RCD.
As shown in fig. 5, when an electric shock accident occurs, a current I flows through the human body T With residual current I RC Is detected by the RCD, which is based on I RC Judging the severity of the danger, triggering protection under the condition that the severity reaches a limit value, and disconnecting the power supply to ensure personal safety.
The residual current protector for the direct current RCD mainly comprises a current transformer, a distinguishing element, an executing element, an electronic signal amplifier, a test device and the like, and the detection of micro direct current is generally realized by adopting a fluxgate principle. Because a certain ripple voltage and a common mode voltage exist in the direct current power supply, even if no electric shock accident occurs, some alternating current leakage currents are formed through the stray capacitance of the cable to the ground, and the leakage currents are also in the form of residual currents and are detected by the current transformer of the RCD, interference is generated on the detection and analysis of the direct current residual current, and further the detection and protection precision of the direct current RCD are affected.
Based on the above, the application provides a scheme for reducing the influence of the alternating current leakage current on the direct current residual current detection, and the degree of the influence of the alternating current leakage current on the RCD of the direct current power supply system can be reduced. Because the alternating current leakage current only has an interference effect on the direct current RCD, no matter how much alternating current leakage current is detected by the direct current RCD, alternating current components in the residual current are counteracted by a certain method, and the influence of the alternating current components is avoided.
As shown in fig. 3, the RCD measures the phasor sum of the currents of the positive and negative poles by magnetic induction, thereby obtaining the residual current of the system, adding a compensation winding on the basis of the original measurement winding, and injecting a current with the same magnitude and opposite direction as the ac measurement value into the compensation winding by the compensation power supply, so as to eliminate the ac component. Firstly, extracting an alternating current component in residual current measured by a measuring winding to be used as a controlled quantity of a PI control loop shown in figure 2; in fig. 2, the PI control loop targets to control the ac component in the measurement winding to be 0, the feedback quantity is the ac component value, and the PI calculates and outputs the compensation power value so that the ac component in the compensation winding can be offset with the ac residual current. The residual current of human body in electric shock is direct current, and the frequency of alternating current leakage current is high frequency, generally above 10kHz, so the method for obtaining alternating current residual current can be divided into two types: (1) performing fast Fourier transform on the measured residual current, and then acquiring an alternating current part of a main frequency band; (2) the alternating current component is directly separated by a filter.
In addition, a design of adding an auxiliary winding on the common-mode magnetic core can be adopted on the basis of the common-mode filter. Based on the residual current I detected by the current sensor RC Analysis is performed to calculate the component I related to the switching frequency S . According to I S Generates a compensation current I C Based on the residual current I RC And I S Regulating compensation current I C Up to residual current I RC Middle I S Minimum.
In order to avoid the influence of alternating current leakage current, the application eliminates alternating current components in the residual current when measuring the residual current, thereby avoiding the influence on the action of direct current RCD.
In the description of the present specification, reference to the terms "some embodiments," "other embodiments," "desired embodiments," and the like, means 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 application. In this specification, schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (9)
1. The direct-current residual current protector is characterized by comprising a current sensor, an alternating-current counteracting device, an executing device, a signal amplifier and a control device, wherein the current sensor and the alternating-current counteracting device are arranged on a direct-current circuit of a direct-current power supply system, the control device is connected with the current sensor through the signal amplifier, and the control device is also connected with the executing device and the alternating-current counteracting device;
the control device is used for converting or filtering the residual current detected by the current sensor to obtain alternating current leakage current in the direct current circuit, obtaining a compensation power supply value according to the alternating current leakage current, injecting current with the same magnitude and opposite direction as the alternating current leakage current into the alternating current counteracting device according to the compensation power supply value, and controlling the alternating current counteracting device to generate alternating current so as to counteract the alternating current leakage current in the direct current circuit;
the control device is also used for disconnecting the power supply of the direct current power supply system through the execution device when the direct current residual current detected by the current sensor is larger than a preset threshold value after the alternating current leakage current in the direct current line is counteracted.
2. The dc residual current protector according to claim 1, wherein the control device performs PI calculation based on the ac leakage current to obtain a compensation power supply value.
3. The dc residual current protector according to claim 2, wherein the control device performs PI calculation to output the compensation power supply value with the ac leakage current as the controlled amount of the PI control loop, the PI control loop targeting to control the ac component in the measurement winding of the current sensor to be 0.
4. The direct current residual current protector according to claim 1, wherein the control device performs a fast fourier transform on the residual current measured by the current sensor to obtain an alternating current leakage current.
5. The dc residual current protector according to claim 1, wherein the ac cancellation device comprises a common mode magnetic core, a common mode filter inductance and an auxiliary winding, the common mode filter inductance and the auxiliary winding are disposed on the common mode magnetic core, the common mode filter inductance is connected in series with the dc line, and the auxiliary winding is connected to the control device.
6. The dc residual current protector according to claim 1, wherein the ac cancellation means includes a compensation winding and a compensation power supply, the compensation power supply connecting the compensation winding and the control means.
7. A method for protecting a dc residual current, comprising:
acquiring residual current detected by a current sensor; the current sensor is arranged on a direct current circuit of the direct current power supply system and is connected with the control device through the signal amplifier;
converting or filtering the residual current to obtain alternating current leakage current in the direct current circuit;
obtaining a compensation power supply value according to the alternating current leakage current, injecting current with the same size and opposite direction as the alternating current leakage current into an alternating current counteracting device according to the compensation power supply value, and controlling the alternating current counteracting device to generate alternating current so as to counteract the alternating current leakage current in the direct current circuit; the alternating current counteracting device is arranged on a direct current circuit of the direct current power supply system;
when the alternating current leakage current in the direct current line is counteracted and the direct current residual current detected by the current sensor is larger than a preset threshold value, the power supply of the direct current power supply system is disconnected through an executing device, and the executing device and the alternating current counteraction device are respectively connected with the control device.
8. A direct current supply system comprising a direct current residual current protector according to any one of claims 1-6.
9. The dc power supply system of claim 8, further comprising a dc link connecting the power source and the powered device.
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