Fault current-limiting stability circuit of virtual synchronous generator

Abstract

The utility model discloses a fault current-limiting stability circuit of a virtual synchronous generator, which relates to the technical field of virtual synchronous generators and comprises a power supply module used for supplying power; the current limiting protection module is used for electric energy transmission and current limiting processing; the virtual synchronous power generation module is used for performing inversion processing and outputting three-phase alternating current electric energy; the over-current detection module is used for current detection and over-current judgment; the overcurrent judgment module is used for carrying out signal transmission and voltage comparison when current limiting work is carried out; the power-off protection module is used for carrying out overcurrent detection and power-off protection again when the current limiting work is carried out; and the power grid module is used for receiving electric energy and supplying power to a connected alternating-current power grid. The fault current-limiting stability circuit of the virtual synchronous generator can carry out current-limiting work when a sag fault occurs in the voltage of a power grid, simultaneously judges whether the electric energy current after current limiting is in a safety range, stops overcurrent work if the electric energy current is lower than the safety range, and cuts off power if the electric energy current is higher than the safety range.

Description

Technical Field

[0001] The utility model relates to the technical field of virtual synchronous generators, and specifically to a virtual synchronous generator fault current limiting and stability circuit. Background Technique

[0002] By simulating the operating characteristics of synchronous generators, virtual synchronous generators add inertia and droop control to frequency and voltage amplitude control, making them have virtual inertia and damping, which can effectively improve traditional grid connection control. During the operation of actual power systems, faults such as voltage sags, three-phase unbalances, and harmonic distortions often occur, which are likely to reduce the stability of virtual synchronous generators and the power grid. When the grid voltage drops in the existing virtual synchronous generators, to avoid overcurrent output, the virtual synchronous generator will be directly controlled to disconnect from the grid or current limiting protection control will be carried out on the virtual synchronous generator to avoid damage to the virtual synchronous generator. Directly disconnecting from the grid will cause power fluctuations in the grid and affect the stability of the grid. When carrying out current limiting protection, if it is in an overcurrent state for a long time, it will lead to frequent switching of current limiting protection, and the degree of current limiting protection is limited, and it cannot ensure whether it is in a safe power supply state after current limiting, so it needs to be improved. Content of the Utility Model

[0003] An embodiment of the utility model provides a virtual synchronous generator fault current limiting and stability circuit to solve the problems raised in the above background technique.

[0004] To achieve the above object, the utility model provides the following technical solutions:

[0005] A virtual synchronous generator fault current limiting and stability circuit includes: a power supply module, a current limiting protection module, a virtual synchronous power generation module, an overcurrent detection module, an overcurrent judgment module, a power-off protection module, and a power grid module;

[0006] The power supply module is used to access DC electrical energy and filter it;

[0007] The current limiting protection module is connected to the power supply module, the virtual synchronous power generation module, the overcurrent detection module, and the overcurrent judgment module, and is used to transmit DC electrical energy to the virtual synchronous power generation module. When receiving the first control signal output by the overcurrent detection module or the second control signal output by the overcurrent judgment module, it performs current limiting processing on the DC electrical energy and transmits the current-limited electrical energy to the virtual synchronous power generation module;

[0008] The virtual synchronous power generation module is used to invert the electrical energy transmitted by the current limiting protection module and output three-phase AC electrical energy;

[0009] An overcurrent detection module, connected to the virtual synchronous power generation module, is used to detect the current of the three-phase AC electrical energy output by the virtual synchronous power generation module, convert the detected current signal into a voltage signal, perform voltage amplification processing on the voltage signal and output a first detection signal, and output a first control signal when the first detection signal is greater than a set first overcurrent threshold;

[0010] An overcurrent judgment module, connected to the overcurrent detection module, is used to receive the first detection signal and a set first voltage threshold when receiving the first control signal, and output a second control signal when the first detection signal is greater than the set first voltage threshold;

[0011] A power-off protection module, connected to the overcurrent judgment module and the virtual synchronous power generation module, is used to transmit the three-phase AC electrical energy to the power grid module, set a second overcurrent threshold and stop transmitting the three-phase AC electrical energy when the first detection signal received by the overcurrent judgment module is greater than the set second overcurrent threshold;

[0012] A power grid module, connected to the power-off protection module, is used to receive the three-phase AC transmitted by the power-off protection module and supply power to the connected AC power grid.

[0013] As a further solution of the present invention: The power supply module includes an input interface and a first capacitor; the current limiting protection module includes a first resistor, a second resistor, a first power tube and a first switch tube;

[0014] Preferably, the first end of the input interface is connected to the drain of the first power tube, one end of the first resistor and one end of the second resistor, and is connected to the second end of the input interface, the emitter of the first switch tube and the ground terminal through the first capacitor. The gate of the first power tube is connected to the other end of the first resistor and the collector of the first switch tube. The source of the first power tube is connected to the other end of the second resistor and the virtual synchronous power generation module.

[0015] As a further solution of the present invention: The virtual synchronous power generation module includes a first inverter, a first inductor, a second inductor, a third inductor, a third resistor, a fourth resistor and a fifth resistor; the overcurrent detection module includes a first current transformer; the power-off protection module includes a first circuit breaker switch; the power grid module includes an AC power grid interface;

[0016] Preferably, the first end of the first inverter is connected to the source electrode of the first power transistor, the second end of the first inverter is connected to the emitter of the first switching transistor, the third end of the first inverter passes through the center of the first current transformer and is connected to one end of the first inductor, the other end of the first inductor is connected to the first moving end of the first disconnecting switch through the third resistor, the fourth end of the first inverter is sequentially connected to the second moving end of the first disconnecting switch through the second inductor and the fourth resistor, and the fifth end of the first inverter is sequentially connected to the third moving end of the first disconnecting switch through the third inductor and the fifth resistor. The first stationary end, the second stationary end, and the third stationary end of the first disconnecting switch are respectively connected to the first end, the second end, and the third end of the AC grid interface.

[0017] As a further aspect of the present invention: The overcurrent detection module further includes a sixth resistor, a first diode, a second capacitor, a seventh resistor, an eighth resistor, a first operational amplifier, a ninth resistor, a first comparator, an eleventh resistor, a tenth resistor, and a first power supply;

[0018] Preferably, the anode of the first diode is connected to the first output terminal of the first current transformer and is connected to the second output terminal of the first current transformer, one end of the second capacitor, one end of the seventh resistor, and the non-inverting terminal of the first operational amplifier through the sixth resistor. The cathode of the first diode is connected to the other end of the second capacitor and the other end of the seventh resistor and is connected to one end of the ninth resistor and the inverting terminal of the first operational amplifier through the eighth resistor. The other end of the ninth resistor is connected to the output terminal of the first operational amplifier and the non-inverting terminal of the first comparator. The inverting terminal of the first comparator is connected to one end of the tenth resistor and is grounded through the eleventh resistor. The output terminal of the first comparator is connected to the overcurrent determination module.

[0019] As a further aspect of the present invention: The overcurrent determination module includes a first analog switch, a second comparator, a second power supply, a twelfth resistor, a second diode, a third switching transistor, and a thirteenth resistor;

[0020] Preferably, the IN terminal of the first analog switch is connected to the output terminal of the first operational amplifier. The CTRL terminal of the first analog switch is connected to the output terminal of the first comparator, the cathode of the second diode, the base of the first switching transistor, and the base of the third switching transistor. The OUT terminal of the first analog switch is connected to the non-inverting terminal of the second comparator. The inverting terminal of the second comparator is connected to the emitter of the third switching transistor and is grounded through the thirteenth resistor. The collector of the third switching transistor is connected to the second power supply through the twelfth resistor. The output terminal of the second comparator is connected to the cathode of the second diode.

[0021] As a further aspect of the present invention: The power-off protection module further includes a third comparator, a fourteenth resistor, a fifteenth resistor, a third power supply, a second switching transistor, a first circuit breaker, and a fourth power supply;

[0022] Preferably, the non-inverting input terminal of the third comparator is connected to the OUT terminal of the first analog switch, the inverting input terminal of the third comparator is connected to one end of the fifteenth resistor and connected to the third power supply through the fourteenth resistor, the other end of the fifteenth resistor is grounded, the output terminal of the third comparator is connected to the base of the second switching transistor, the emitter of the second switching transistor is grounded, and the collector of the second switching transistor is connected to one end of the first circuit breaker, and the other end of the first circuit breaker is connected to the fourth power supply.

[0023] Compared with the prior art, the beneficial effects of the present utility model are as follows: The fault current limiting stability circuit of the virtual synchronous generator of the present utility model can supply electric energy to the power grid module by the virtual synchronous power generation module cooperating with the power supply module. When a voltage sag fault occurs in the power grid voltage, the overcurrent detection module will detect that the virtual synchronous power generation module has an overcurrent. At this time, the current limiting protection module will be controlled to perform current limiting work. At the same time, the overcurrent judgment module cooperates with the power-off protection module to judge whether the current of the electric energy after current limiting is within the safe range. If it is lower than the safe range, it means that the current is normal, and the overcurrent work will be stopped at this time. If the current of the electric energy after current limiting is still higher than the safe range, the connection between the virtual synchronous power generation module and the power grid module will be disconnected, effectively improving the safety and stability of the virtual synchronous power generation module. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings required for the description of the embodiments of the present utility model will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a schematic block diagram of the principle of a fault current limiting stability circuit of a virtual synchronous generator provided by an embodiment of the present utility model.

[0026] Figure 2 It is a circuit diagram of a fault current limiting stability circuit of a virtual synchronous generator provided by an embodiment of the present utility model.

[0027] Figure 3 It is a connection circuit diagram of the power-off protection module provided by an embodiment of the present utility model. Detailed Embodiments

[0028] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present utility model.

[0029] In one embodiment, refer to Figure 1 A virtual synchronous generator fault current limiting stability circuit includes: a power supply module 1, a current limiting protection module 2, a virtual synchronous power generation module 3, an overcurrent detection module 4, an overcurrent judgment module 5, a power-off protection module 6, and a power grid module 7;

[0030] Specifically, the power supply module 1 is used to access DC electrical energy and perform filtering;

[0031] The current limiting protection module 2 is connected to the power supply module 1, the virtual synchronous power generation module 3, the overcurrent detection module 4, and the overcurrent judgment module 5, and is used to transmit DC electrical energy to the virtual synchronous power generation module 3. When receiving the first control signal output by the overcurrent detection module 4 or the second control signal output by the overcurrent judgment module 5, it performs current limiting processing on the DC electrical energy and transmits the current-limited electrical energy to the virtual synchronous power generation module 3;

[0032] The virtual synchronous power generation module 3 is used to invert the electrical energy transmitted by the current limiting protection module 2 and output three-phase AC electrical energy;

[0033] The overcurrent detection module 4 is connected to the virtual synchronous power generation module 3, and is used to detect the current of the three-phase AC electrical energy output by the virtual synchronous power generation module 3, convert the detected current signal into a voltage signal, perform voltage amplification processing on the voltage signal and output a first detection signal. When the first detection signal is greater than the set first overcurrent threshold, it outputs a first control signal;

[0034] The overcurrent judgment module 5 is connected to the overcurrent detection module 4, and is used to receive the first detection signal and the set first voltage threshold when receiving the first control signal. When the first detection signal is greater than the set first voltage threshold, it outputs a second control signal;

[0035] The power-off protection module 6 is connected to the overcurrent judgment module 5 and the virtual synchronous power generation module 3, and is used to transmit three-phase AC electrical energy to the power grid module 7, set a second overcurrent threshold, and stop transmitting three-phase AC electrical energy when the first detection signal received by the overcurrent judgment module 5 is greater than the set second overcurrent threshold;

[0036] The power grid module 7 is connected to the power-off protection module 6, and is used to receive the three-phase AC transmitted by the power-off protection module 6 and supply power to the connected AC power grid.

[0037] In a specific embodiment, the above-mentioned power supply module 1 can adopt a power supply circuit composed of an input interface and a capacitor, which can access DC electrical energy and perform filtering; the above-mentioned current limiting protection module 2 can adopt a current limiting protection circuit composed of a field effect transistor, a resistor and a triode, which can perform power transmission or current limiting work; the above-mentioned virtual synchronous power generation module 3 can adopt a virtual synchronous power generation circuit composed of an inverter, an inductor and a resistor, which can perform inversion and filtering processing on the input electrical energy; the above-mentioned overcurrent detection module 4 can adopt an overcurrent detection circuit composed of a current transformer, a comparator, a diode, an operational amplifier, etc., which can perform current sampling on the electrical energy output by the virtual synchronous power generation module 3, convert the sampled current signal into a voltage signal, and then perform signal amplification and filtering processing, and can set a first overcurrent threshold, so that when the processed signal is greater than the overcurrent threshold, overcurrent judgment is performed; the above-mentioned overcurrent judgment module 5 can adopt an overcurrent judgment circuit composed of an analog switch, a comparator, a triode, etc., which can set a first voltage threshold, and this first voltage threshold is used to detect whether the current of the electrical energy after current limiting is in an undercurrent state during current limiting protection; the above-mentioned power-off protection module 6 can adopt a power-off protection circuit composed of a circuit breaker, a comparator, a triode, etc., which can set a second overcurrent threshold, and this second overcurrent threshold is used to detect whether the current of the electrical energy after current limiting is still in an overcurrent state during current limiting protection; the above-mentioned power grid module 7 can adopt a power grid circuit composed of an AC power grid interface, which can be connected to the AC power grid to complete the electrical energy interaction with the virtual synchronous power generation module 3.

[0038] In another embodiment, please refer to Figure 1 、 Figure 2 and Figure 3 , the power supply module 1 includes an input interface and a first capacitor C1; the current limiting protection module 2 includes a first resistor R1, a second resistor R2, a first power tube Q1 and a first switch tube V1;

[0039] Specifically, the first end of the input interface is connected to the drain of the first power tube Q1, one end of the first resistor R1 and one end of the second resistor R2, and is connected to the second end of the input interface, the emitter of the first switch tube V1 and the ground terminal through the first capacitor C1. The gate of the first power tube Q1 is connected to the other end of the first resistor R1 and the collector of the first switch tube V1. The source of the first power tube Q1 is connected to the other end of the second resistor R2 and the virtual synchronous power generation module 3.

[0040] In a specific embodiment, the above-mentioned second resistor R2 is used as a current limiting resistor; the above-mentioned first power tube Q1 can be selected as an N-channel field effect transistor; the above-mentioned first switch tube V1 can be selected as an NPN type triode.

[0041] Further, the virtual synchronous power generation module 3 includes a first inverter T1, a first inductor L1, a second inductor L2, a third inductor L3, a third resistor R3, a fourth resistor R4, and a fifth resistor R5; the overcurrent detection module 4 includes a first current transformer CT1; the power-off protection module 6 includes a first circuit breaker K1-1; the power grid module 7 includes an AC power grid interface.

[0042] Specifically, the first end of the first inverter T1 is connected to the source electrode of the first power transistor Q1, the second end of the first inverter T1 is connected to the emitter of the first switch tube V1, the third end of the first inverter T1 passes through the center of the first current transformer CT1 and is connected to one end of the first inductor L1, the other end of the first inductor L1 is connected to the first moving end of the first circuit breaker K1-1 through the third resistor R3, the fourth end of the first inverter T1 is sequentially connected to the second moving end of the first circuit breaker K1-1 through the second inductor L2 and the fourth resistor R4, the fifth end of the first inverter T1 is sequentially connected to the third moving end of the first circuit breaker K1-1 through the third inductor L3 and the fifth resistor R5, and the first stationary end, the second stationary end, and the third stationary end of the first circuit breaker K1-1 are respectively connected to the first end, the second end, and the third end of the AC power grid interface.

[0043] In a specific embodiment, the above-mentioned first inverter T1 can be composed of six groups of IGBTs, controlled by a single-chip microcomputer, to invert the input DC electric energy and output three-phase AC electric energy; the above-mentioned first current transformer CT1 can be selected as a current transformer; the above-mentioned first circuit breaker K1-1 can adopt a normally closed three-pole three-throw switch.

[0044] Further, the overcurrent detection module 4 further includes a sixth resistor R6, a first diode D1, a second capacitor C2, a seventh resistor R7, an eighth resistor R8, a first operational amplifier OP1, a ninth resistor R9, a first comparator A1, an eleventh resistor R11, a tenth resistor R10, and a first power supply VCC1.

[0045] Specifically, the anode of the first diode D1 is connected to the first output terminal of the first current transformer CT1 and is connected to the second output terminal of the first current transformer CT1, one end of the second capacitor C2, one end of the seventh resistor R7, and the non-inverting terminal of the first operational amplifier OP1 through the sixth resistor R6, the cathode of the first diode D1 is connected to the other end of the second capacitor C2 and the other end of the seventh resistor R7 and is connected to one end of the ninth resistor R9 and the inverting terminal of the first operational amplifier OP1 through the eighth resistor R8, the other end of the ninth resistor R9 is connected to the output terminal of the first operational amplifier OP1 and the non-inverting terminal of the first comparator A1, the inverting terminal of the first comparator A1 is connected to one end of the tenth resistor R10 and is grounded through the eleventh resistor R11, and the output terminal of the first comparator A1 is connected to the overcurrent judgment module 5.

[0046] In a specific embodiment, the above-mentioned sixth resistor R6, first diode D1, second capacitor C2, and seventh resistor R7 perform current-voltage conversion and filtering; the above-mentioned first operational amplifier OP1 can select an OP07 operational amplifier, and the chip day, eighth resistor R8, and ninth resistor R9 perform signal amplification; the above-mentioned first power supply VCC1, eleventh resistor R11, and tenth resistor R10 set the first overcurrent threshold; the above-mentioned first comparator A1 can select an LLM358 comparator.

[0047] Further, the overcurrent determination module 5 includes a first analog switch IC1, a second comparator A2, a second power supply VCC2, a twelfth resistor R12, a second diode D2, a third switching transistor V3, and a thirteenth resistor R13;

[0048] Specifically, the IN terminal of the first analog switch IC1 is connected to the output terminal of the first operational amplifier OP1, the CTRL terminal of the first analog switch IC1 is connected to the output terminal of the first comparator A1, the cathode of the second diode D2, the base of the first switching transistor V1, and the base of the third switching transistor V3. The OUT terminal of the first analog switch IC1 is connected to the non-inverting terminal of the second comparator A2. The inverting terminal of the second comparator A2 is connected to the emitter of the third switching transistor V3 and grounded through the thirteenth resistor R13. The collector of the third switching transistor V3 is connected to the second power supply VCC2 through the twelfth resistor R12, and the output terminal of the second comparator A2 is connected to the cathode of the second diode D2.

[0049] In a specific embodiment, the above-mentioned first analog switch IC1 can select a CD4066 analog switch; the above-mentioned second comparator A2 can select an LM358 comparator; the above-mentioned third switching transistor V3 can select an NPN-type triode, and cooperate with the second power supply VCC2, twelfth resistor R12, and thirteenth resistor R13 to set the first voltage threshold.

[0050] Further, the power-off protection module 6 further includes a third comparator A3, a fourteenth resistor R14, a fifteenth resistor R15, a third power supply VCC3, a second switching transistor V2, a first circuit breaker K1, and a fourth power supply VCC4;

[0051] Specifically, the non-inverting terminal of the third comparator A3 is connected to the OUT terminal of the first analog switch IC1. The inverting terminal of the third comparator A3 is connected to one end of the fifteenth resistor R15 and connected to the third power supply VCC3 through the fourteenth resistor R14. The other end of the fifteenth resistor R15 is grounded. The output terminal of the third comparator A3 is connected to the base of the second switching transistor V2. The emitter of the second switching transistor V2 is grounded. The collector of the second switching transistor V2 is connected to one end of the first circuit breaker K1, and the other end of the first circuit breaker K1 is connected to the fourth power supply VCC4.

[0052] In a specific embodiment, the third comparator A3 may be an LM358 comparator; the third power supply VCC3, the fourteenth resistor R14, and the fifteenth resistor R15 set a second overcurrent threshold; the second switching transistor V2 may be an NPN-type triode; the first circuit breaker K1 controls the disconnection of the first disconnection switch K1-1.

[0053] In the fault current limiting and stability circuit of a virtual synchronous generator in this embodiment, the input interface can be connected to a solar cell or a storage battery to access DC electrical energy. The first capacitor C1 performs filtering, the first power transistor Q1 performs electrical energy transmission, and the first inverter T1 performs inversion to invert the DC electrical energy into three-phase AC electrical energy and transmits it to the AC power grid connected to the AC power grid interface through the first disconnection switch K1-1 to improve the stability of the AC power grid. The first current transformer CT1 cooperates with the sixth resistor R6, the first diode D1, the second capacitor C2, the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, and the first operational amplifier OP1 to sample the output three-phase AC electrical energy and convert the current signal into a voltage signal. When faults such as voltage sags and three-phase unbalances occur in the AC power grid, they will all cause overcurrent, affecting the first inverter T1. At the same time, the converted voltage signal will be greater than the first overcurrent threshold set by the first power supply VCC1, the eleventh resistor R11, and the tenth resistor R10. The first comparator A1 outputs a high level, controlling the CTRL terminal of the first analog switch IC1 to become high level. The third switching transistor V3 conducts, the first switching transistor V1 conducts, the first power transistor Q1 cuts off, and the second resistor R2 performs current limiting. The first analog switch IC1 transmits the converted voltage signal to the non-inverting terminal of the second comparator A2 and the non-inverting terminal of the third comparator A3. After current limiting, when the signal sampled by the first current transformer CT1 is greater than the first voltage threshold set by the second power supply VCC2, the twelfth resistor R12, the third switching transistor V3, and the thirteenth resistor R13 after being processed, it indicates that the three-phase AC electrical energy without current limiting is still in an overcurrent state. The second comparator A2 will output a high level to maintain the conduction of the third switching transistor V3, the conduction of the first switching transistor V1, and the first analog switch IC1 for signal transmission until the sampled and processed signal after current limiting is lower than the first voltage threshold, indicating that the original three-phase AC electrical energy has returned to normal. If the signal after current limiting is greater than the second overcurrent threshold set by the third power supply VCC3, the fourteenth resistor R14, and the fifteenth resistor R15, it indicates that the electrical energy after current limiting is still in an overcurrent state. At this time, the second switching transistor V2 conducts, and the first circuit breaker K1 controls the disconnection of the first disconnection switch K1-1 to disconnect the connection with the AC power grid.

[0054] For those skilled in the art, it is obvious that the present utility model is not limited to the details of the above-described exemplary embodiments, and the present utility model can be implemented in other specific forms without departing from the spirit or basic characteristics of the present utility model. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present utility model is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present utility model. Any reference signs in the claims should not be construed as limiting the claims involved.

[0055] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A virtual synchronous generator fault current limiting stability circuit, characterized in that: The virtual synchronous generator fault current limiting stability circuit comprises: a power supply module, a current limiting protection module, a virtual synchronous power generation module, an overcurrent detection module, an overcurrent judgment module, a power failure protection module and a power grid module; The power module is used to receive direct current power and perform filtering; The current limiting protection module is connected to the power supply module, the virtual synchronous power generation module, the overcurrent detection module and the overcurrent judgment module, and is used to transmit the DC power to the virtual synchronous power generation module, and when receiving the first control signal output by the overcurrent detection module or the second control signal output by the overcurrent judgment module, the DC power is current limited and the power after current limiting is transmitted to the virtual synchronous power generation module; The virtual synchronous power generation module is used to invert the electric energy transmitted by the current limiting protection module and output three-phase AC electric energy; The overcurrent detection module is connected to the virtual synchronous power generation module, and is used to perform current detection on the three-phase AC power output by the virtual synchronous power generation module, and convert the detected current signal into a voltage signal, perform voltage amplification processing on the voltage signal and output a first detection signal, and output a first control signal when the first detection signal is greater than a set first overcurrent threshold; The overcurrent judgment module is connected to the overcurrent detection module, and is used to receive a first detection signal and set a first voltage threshold when receiving a first control signal, and output a second control signal when the first detection signal is greater than the set first voltage threshold; The power-off protection module is connected to the overcurrent judgment module and the virtual synchronous power generation module, and is used to transmit the three-phase AC power to the power grid module, set a second overcurrent threshold, and stop transmitting the three-phase AC power when the first detection signal received by the overcurrent judgment module is greater than the set second overcurrent threshold; The power grid module is connected to the power failure protection module and is used to receive the three-phase AC transmitted by the power failure protection module and supply power to the connected AC power grid.

2. A virtual synchronous generator fault current limiting stability circuit according to claim 1, characterized in that: The power supply module includes an input interface and a first capacitor; the current limiting protection module includes a first resistor, a second resistor, a first power tube and a first switch tube; The first end of the input interface is connected to the drain of the first power tube, one end of the first resistor and one end of the second resistor, and the second end of the input interface, the emitter of the first switch tube and the ground end are connected through the first capacitor. The gate of the first power tube is connected to the other end of the first resistor and the collector of the first switch tube. The source of the first power tube is connected to the other end of the second resistor and the virtual synchronous power generation module.

3. A virtual synchronous generator fault current limiting stability circuit according to claim 2, characterized in that: The virtual synchronous power generation module includes a first inverter, a first inductor, a second inductor, a third inductor, a third resistor, a fourth resistor and a fifth resistor; the overcurrent detection module includes a first mutual inductor; the power failure protection module includes a first circuit breaker; the power grid module includes an AC power grid interface; The first end of the first inverter is connected to the source of the first power tube, the second end of the first inverter is connected to the emitter of the first switch tube, the third end of the first inverter passes through the center of the first mutual inductor and is connected to one end of the first inductor, the other end of the first inductor is connected to the first moving end of the first circuit breaker through the third resistor, the fourth end of the first inverter is connected to the second moving end of the first circuit breaker through the second inductor and the fourth resistor in sequence, the fifth end of the first inverter is connected to the third moving end of the first circuit breaker through the third inductor and the fifth resistor in sequence, and the first static end, the second static end and the third static end of the first circuit breaker are respectively connected to the first end, the second end and the third end of the AC power grid interface.

4. A virtual synchronous generator fault current limiting stability circuit according to claim 3, characterized in that: The overcurrent detection module also includes a sixth resistor, a first diode, a second capacitor, a seventh resistor, an eighth resistor, a first operational amplifier, a ninth resistor, a first comparator, an eleventh resistor, a tenth resistor and a first power supply; The anode of the first diode is connected to the first output end of the first mutual inductor and is connected to the second output end of the first mutual inductor, one end of the second capacitor, one end of the seventh resistor and the non-inverting end of the first operational amplifier through the sixth resistor. The cathode of the first diode is connected to the other end of the second capacitor and the other end of the seventh resistor and is connected to one end of the ninth resistor and the inverting end of the first operational amplifier through the eighth resistor. The other end of the ninth resistor is connected to the output end of the first operational amplifier and the non-inverting end of the first comparator. The inverting end of the first comparator is connected to one end of the tenth resistor and is grounded through the eleventh resistor. The output end of the first comparator is connected to the overcurrent judgment module.

5. A virtual synchronous generator fault current limiting stability circuit according to claim 4, characterized in that: The overcurrent judgment module includes a first analog switch, a second comparator, a second power supply, a twelfth resistor, a second diode, a third switch tube and a thirteenth resistor; The IN terminal of the first analog switch is connected to the output terminal of the first operational amplifier, the CTRL terminal of the first analog switch is connected to the output terminal of the first comparator, the cathode of the second diode, the base of the first switch tube and the base of the third switch tube, the OUT terminal of the first analog switch is connected to the non-inverting terminal of the second comparator, the inverting terminal of the second comparator is connected to the emitter of the third switch tube and grounded through a thirteenth resistor, the collector of the third switch tube is connected to the second power supply through a twelfth resistor, and the output terminal of the second comparator is connected to the cathode of the second diode.

6. A virtual synchronous generator fault current limiting stability circuit according to claim 5, characterized in that: The power-off protection module further includes a third comparator, a fourteenth resistor, a fifteenth resistor, a third power supply, a second switch tube, a first circuit breaker and a fourth power supply; The non-inverting end of the third comparator is connected to the OUT end of the first analog switch, the inverting end of the third comparator is connected to one end of the fifteenth resistor and is connected to the third power supply through the fourteenth resistor, the other end of the fifteenth resistor is grounded, the output end of the third comparator is connected to the base of the second switch tube, the emitter of the second switch tube is grounded, the collector of the second switch tube is connected to one end of the first circuit breaker, and the other end of the first circuit breaker is connected to the fourth power supply.

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