Flexible arc extinction device with series voltage division of phase power supply

Abstract

The application provides a flexible fusion arc-extinguishing device with phase power series voltage division. The topological structure is a structure in which a phase power and a single-phase converter are connected in series through an isolation transformer, wherein the phase power is obtained through switching and voltage boosting of a secondary winding of a grounding transformer and voltage boosting of a voltage transformer, the single-phase converter is connected in series with the phase power through the isolation transformer, and a DC side power supply of the single-phase converter is provided through rectification of the secondary winding of the grounding transformer by a rectifier. The control algorithm of the flexible fusion arc-extinguishing device is that the phase power is controlled as a voltage source, and the single-phase converter is controlled as a current source. The technical scheme makes up for the deficiency of the voltage arc-extinguishing method that the fault current compensation effect is not obvious in low-resistance grounding fault, and has good engineering application value.

Description

Technical Field

[0001] This invention relates to the field of arc suppression device technology, and in particular to a flexible fusion arc suppression device with phase power supply series voltage division. Background Technology

[0002] With the rapid development of Chinese society, the scale of power distribution networks has gradually increased, leading to a corresponding increase in ground fault current. Furthermore, due to the widespread use of nonlinear components and cable lines, the proportion of harmonic and active components in ground fault current has significantly increased. Traditional arc suppression coils cannot effectively compensate for the harmonic and active components in ground fault current, making it difficult for the ground fault arc to extinguish itself. This increases the risk of further fault development, such as the potential for arc overvoltage, damage to power distribution network equipment, or development into phase-to-phase short-circuit faults, and even the possibility of fire. Flexible (active) arc suppression devices that achieve full compensation of ground fault current using active inverters can effectively solve this problem.

[0003] Based on different topologies, existing flexible arc suppression devices mainly include master-slave type, neutral-point connected type, phase-separated type, and phase-power-feed type. Master-slave type flexible arc suppression devices are generally parallel-connected, with the arc suppression coil acting as the master device to compensate for most of the reactive component of the ground fault current; the slave device consists of a single-phase inverter connected in parallel across the arc suppression coil via a step-up transformer to compensate for the harmonic and active components of the ground fault current. Neutral-point connected type flexible arc suppression devices are connected to the distribution network via a single-phase inverter, a step-up transformer, and a Z-type grounding transformer to achieve full compensation for the ground fault current. Phase-separated type flexible arc suppression devices are directly connected to the distribution network bus or line via a three-phase cascaded H-bridge converter, with the three-phase common point directly grounded or grounded via a switch to achieve full compensation for the ground fault current. The phase power supply-feed flexible arc suppression device takes its source from the secondary side of the Z-type grounding transformer. The secondary winding of the Z-type grounding transformer is connected to the secondary side of the step-up transformer after being connected in series or in parallel with the converter via a switch. The switch is used to adjust the voltage phase of the secondary winding. Through the coordinated control of the converter, the primary voltage of the step-up transformer is made to be the negative value of the fault phase power supply voltage and fed into the neutral point of the distribution network.

[0004] Existing flexible arc suppression devices mainly have the following problems: master-slave type flexible arc suppression devices have fewer output levels and higher switching frequencies; in neutral point connected type and phase-separated type flexible arc suppression devices, the converter bears a large arc suppression capacity; phase power supply fed type flexible arc suppression devices all use voltage arc suppression methods, which have little compensation effect on fault current in the case of low resistance ground faults, and are prone to failure to extinguish the fault arc.

[0005] In addition, in the aforementioned master-slave type flexible arc suppression device and neutral point access type flexible arc suppression device, the converter is connected to the secondary side of the step-up transformer, resulting in a large current flowing through the converter and a high switching frequency, which leads to a serious problem of converter overheating. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a flexible fusion arc suppression device with phase power supply series voltage division. This device can reduce the voltage and current withstand requirements of the converter and the overall manufacturing cost of the flexible arc suppression device while achieving full compensation for ground fault current, and has good engineering application value.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a flexible fusion arc suppression device with phase power supply series voltage division, wherein the topology of the flexible fusion arc suppression device is a structure in which the phase power supply and the single-phase converter are connected in series after passing through an isolation transformer; the control algorithm of the flexible fusion arc suppression device is to control the phase power supply as a voltage source and the single-phase converter as a current source.

[0008] In a preferred embodiment: the phase power supply is obtained by switching the secondary winding of the grounding transformer and stepping up the voltage through a step-up transformer; the single-phase converter is connected in series with the phase power supply after passing through an isolation transformer, or directly connected in series with the phase power supply; the DC power supply of the single-phase converter is provided by the secondary winding of the grounding transformer after rectification by a rectifier; the control target of the voltage source is the negative value of the fault phase power supply voltage, and the setpoint of the control target of the current source is obtained by multiplying the negative value of the fault phase power supply voltage, the system ground admittance, and the current transformation ratio from the secondary side to the primary side of the isolation transformer.

[0009] In a preferred embodiment: taking a single-phase ground fault in phase A as an example, based on the voltage arc suppression principle based on phase power supply input, the following equation holds:

[0010]

[0011] In the formula, The phase voltage of the faulty phase. For ground fault current, R f For ground fault transition resistance, This refers to the phase voltage of phase A in the distribution network. This refers to the voltage of phase A of the power distribution network. The neutral point voltage, This refers to the primary voltage of the step-up transformer.

[0012] According to the principle of voltage arc suppression, if the primary voltage of the step-up transformer is controlled by switching the secondary side switch, the voltage of the step-up transformer can be reduced. From equation (1), we can see that at this time... This enables arc suppression during grounding faults.

[0013] In a preferred embodiment: taking a single-phase ground fault in phase A as an example, based on the current arc suppression principle of injecting fully compensated current into the converter, the following equations apply.

[0014]

[0015] In the formula, These are the three-phase ground currents of the distribution network. This refers to the primary current of a single-phase isolation transformer. For ground fault current, These are the three-phase power supply voltages of the distribution network. These are the three-phase phase voltages of the distribution network. For the neutral point voltage, r A r B r C These are the three-phase-to-ground leakage resistances of the distribution network, C A C B C C These are the equivalent capacitances of the three phases to ground in the distribution network; assuming the turns ratio of the single-phase isolation transformer is 1:k, then the output current of the single-phase converter...

[0016] According to the principle of arc suppression by electric current, let Then equation (2) can be transformed into

[0017]

[0018] Equation (3) is the fundamental component of the compensation current, and the harmonic components of the compensation current can be obtained in the same way.

[0019] According to the principle of current arc suppression, if the primary side current of a single-phase isolation transformer is controlled to be the ground fault full compensation current, and the full compensation current is the vector sum of the fundamental and harmonic components, and injected into the neutral point, the ground fault arc suppression can be achieved.

[0020] Let C A =C B =C C =C0, r A =r B =r C =r0, and has Then equation (3) simplifies to

[0021]

[0022] In the formula, r Σ =r0 / 3, C Σ =3C0. Therefore, the output current of the single-phase converter can be determined as...

[0023]

[0024] The same applies to single-phase grounding faults in phases B and C.

[0025] In a preferred embodiment, the single-phase converter is one of a two-level single-phase half-bridge / full-bridge, a three-level single-phase half-bridge / full-bridge, a multi-level single-phase half-bridge / full-bridge, or a single-phase cascaded H-bridge.

[0026] In a preferred embodiment: the rectifier is a single-phase controlled rectifier, a three-phase controlled rectifier, a single-phase uncontrolled rectifier, or a three-phase uncontrolled rectifier.

[0027] In a preferred embodiment: the isolation transformer and the step-up transformer are two independent single-phase transformers or a single-phase transformer that combines the two.

[0028] In a preferred embodiment, the flexible fusion arc extinguishing device specifically employs the following control method:

[0029] During normal operation, disconnect the switches on the secondary side of the single-phase step-up transformer and the secondary side of the single-phase isolation transformer to open the secondary side of the single-phase step-up transformer and the single-phase isolation transformer. This means that the phase power supply and the single-phase converter are taken out of operation. At this time, the distribution network operates in a neutral point non-effective grounding mode.

[0030] During a ground fault, the state of the switch on the secondary side of the single-phase step-up transformer is adjusted, thereby adjusting the phase of the input voltage on the secondary side of the single-phase step-up transformer. This makes the phase power supply voltage negative of the fault phase power supply voltage and feeds it into the neutral point of the distribution network, using a voltage arc suppression method. Then, the switch on the secondary side of the single-phase isolation transformer is closed, and the current injected into the neutral point of the distribution network through the single-phase converter is controlled to be the full compensation current for the ground fault. Its value is the product of the negative value of the fault phase power supply voltage and the total ground admittance of the distribution network, using a current arc suppression method. The combination of these two methods forms a voltage-current fusion arc suppression method.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The flexible fusion arc suppression device with phase power supply series voltage division proposed in this invention has a passive arc suppression device that bears most of the arc suppression capacity and a flexible (active) arc suppression device that bears a small portion of the arc suppression capacity. Therefore, only a small portion of the neutral point voltage drops across the converter, reducing the voltage withstand requirement of the converter. Theoretically, a single H-bridge converter can meet the requirements.

[0033] 2. The flexible fusion arc suppression device with phase power supply series voltage division proposed in this invention significantly reduces the current flowing through the converter compared to the arc suppression device that uses a converter connected to the neutral point of the distribution network via a step-up transformer. Therefore, the temperature rise of the converter is smaller.

[0034] 3. The flexible fusion arc suppression device with phase power supply series voltage division proposed in this invention is provided by the secondary side of the Z-type grounding transformer after rectifier. The single-phase step-up transformer and single-phase isolation transformer can theoretically be merged into a single-phase transformer, and the overall volume of the device is effectively reduced.

[0035] 4. The flexible fusion arc suppression device with phase power supply series voltage division proposed in this invention adopts a voltage and current fusion arc suppression method, which can effectively compensate for fault current under different ground fault transition resistances. Compared with other phase power supply feeding devices, it has a wider range of applications. In summary, this invention is more advantageous for engineering applications. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the topology and principle of a flexible fusion arc suppression device with series voltage division of phase power supply according to a preferred embodiment of the present invention;

[0037] Figure 2 The calculation equivalent circuit diagram of the flexible fusion arc suppression device with series voltage division of phase power supply according to a preferred embodiment of the present invention is shown below.

[0038] Figure 3 This is a schematic diagram of a simulation model for a preferred embodiment of the present invention.

[0039] Figure 4 This is a schematic diagram of the fault current compensation effect of the flexible fusion arc suppression device with series voltage division of phase power supply in a simulation example of a preferred embodiment of the present invention when the ground fault transition resistance is 1Ω.

[0040] Figure 5 This is a schematic diagram illustrating the fault current compensation effect of the flexible fusion arc suppression device with series voltage division of phase power supply in a simulation example of a preferred embodiment of the present invention when the ground fault transition resistance is 100Ω.

[0041] Figure 6 This is a schematic diagram illustrating the fault current compensation effect of the flexible fusion arc suppression device with series voltage division of phase power supply in a simulation example of a preferred embodiment of the present invention when the ground fault transition resistance is 500Ω.

[0042] Figure 7 This is a schematic diagram illustrating the fault current compensation effect of a flexible fusion arc suppression device with a series voltage divider for phase power supply in a simulation example of a preferred embodiment of the present invention when the transition resistance of the ground fault is 1000Ω. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0044] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, 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 pertains.

[0045] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0046] like Figure 1 and Figure 2 As shown, this embodiment provides the topology, schematic diagram, and equivalent circuit calculation of a flexible fusion arc suppression device with phase power supply series voltage division. The phase power supply is controlled as a voltage source, with the control target being the negative value of the fault phase power supply voltage. The single-phase converter is controlled as a current source, and the setpoint of the control target is obtained by multiplying the negative value of the fault phase power supply voltage, the system ground admittance, and the current ratio from the secondary side to the primary side of the isolation transformer. This achieves full compensation for the ground fault current. The single-phase isolation transformer and the single-phase step-up transformer are two independent single-phase transformers or a single-phase transformer combining both. Figure 1 Taking independent single-phase step-up transformers and single-phase isolation transformers as examples; the single-phase converter is one of the following: two-level single-phase half-bridge / full-bridge, three-level single-phase half-bridge / full-bridge, multi-level single-phase half-bridge / full-bridge, or single-phase cascaded H-bridge. Figure 1 Taking a single-phase three-level full-bridge converter as an example; the rectifier can be one of a single-phase controlled rectifier, a three-phase controlled rectifier, a single-phase uncontrolled rectifier, or a three-phase uncontrolled rectifier. Figure 1 Take the three-phase uncontrolled rectifier as an example.

[0047] The flexible fusion arc suppression device specifically employs the following control method: During normal operation, the switches on the secondary sides of the single-phase step-up transformer and the single-phase isolation transformer are disconnected, opening the secondary sides of both transformers. This means the phase power supply and single-phase converter are taken out of operation, and the distribution network operates in a neutral point non-effectively grounded mode. During a ground fault, the state of the switch on the secondary side of the single-phase step-up transformer is adjusted, thereby adjusting the phase of the input voltage on the secondary side of the transformer. This ensures the phase power supply voltage is negative of the fault phase power supply voltage and is fed into the neutral point of the distribution network, employing a voltage-based arc suppression method. Then, the switch on the secondary side of the single-phase isolation transformer is closed, controlling the current injected into the neutral point of the distribution network through the single-phase converter to be the full compensation current for the ground fault. This current is the product of the negative fault phase power supply voltage and the total ground admittance of the distribution network, employing a current-based arc suppression method. The combination of these two methods forms a voltage-current fusion arc suppression method.

[0048] The technical solution of this embodiment will be described in detail from the perspective of principle as follows:

[0049] 1. Voltage arc suppression principle based on phase power supply input

[0050] like Figure 1 and Figure 2 As shown, according to the control method of the flexible fusion arc suppression device described above, the relevant circuits of the step-up transformer in the primary circuit can be equivalent to a controllable voltage source, with the control target being the negative value of the fault phase power supply voltage; the relevant circuits of the isolation transformer can be equivalent to a controllable current source, and the setpoint of the control target is obtained by multiplying the negative value of the fault phase power supply voltage and the system ground admittance. Taking a single-phase ground fault in phase A as an example, the following equations are given.

[0051]

[0052] In the formula, The phase voltage of the faulty phase. For ground fault current, R f For ground fault transition resistance, This refers to the phase voltage of phase A in the distribution network. This refers to the voltage of phase A of the power distribution network. The neutral point voltage, This refers to the primary voltage of the step-up transformer.

[0053] According to the principle of voltage arc suppression, if the primary voltage of the step-up transformer is controlled by switching the secondary side switch, the voltage of the step-up transformer can be reduced. From equation (1), we can see that at this time... This will enable arc suppression of grounding faults, and the same applies to single-phase grounding faults in phases B and C.

[0054] 2. Current arc suppression principle based on fully compensated current injection into the converter

[0055] like Figure 1 and Figure 2 As shown, taking a single-phase ground fault in phase A as an example, the following equations are given.

[0056]

[0057] In the formula, These are the three-phase ground currents of the distribution network. This refers to the primary current of a single-phase isolation transformer. For ground fault current, These are the three-phase power supply voltages of the distribution network. These are the three-phase phase voltages of the distribution network. For the neutral point voltage, r A r B r C These are the three-phase-to-ground leakage resistances of the distribution network, C A C B C C These are the equivalent capacitances of the three phases to ground in the distribution network; assuming the turns ratio of the single-phase isolation transformer is 1:k, then the output current of the single-phase converter...

[0058] According to the principle of arc suppression by electric current, let Then equation (2) can be transformed into

[0059]

[0060] Equation (3) is the fundamental component of the compensation current, and the harmonic components of the compensation current can be obtained in the same way.

[0061] According to the principle of current arc suppression, if the primary side current of a single-phase isolation transformer is controlled to be the ground fault full compensation current, and the full compensation current is the vector sum of the fundamental and harmonic components, and injected into the neutral point, the ground fault arc suppression can be achieved.

[0062] Let C A =C B =C C =C0, r A =r B =r C =r0, and has Then equation (3) simplifies to

[0063]

[0064] In the formula, r Σ =r0 / 3, C Σ =3C0. Therefore, the output current of the single-phase converter can be determined as...

[0065]

[0066] The same applies to single-phase grounding faults in phases B and C.

[0067] 3. Advantages of the voltage-current fusion arc suppression method

[0068] Depend on Figure 1 and Figure 2 It can be seen that when the step-up transformer works alone, the voltage arc suppression method is used to feed the negative value of the fault phase power supply voltage to the neutral point. However, the transformer has certain losses. If the converter still uses the voltage arc suppression method for control, when a low-resistance grounding occurs, especially a metallic grounding, the comprehensive error of the device will lead to a large fault residual current, resulting in the fault arc not being extinguished.

[0069] Therefore, the converter should adopt a current arc suppression method, and control the output current through a current closed-loop control. To compensate for errors in voltage arc suppression methods, the flexible fusion arc suppression device with series voltage division of phase power supplies can effectively compensate for fault current under different ground fault transition resistances.

[0070] As can be seen from the above, the converter is mainly used to output the product of the difference between the primary voltage of the step-up transformer and the negative value of the fault phase power supply voltage and the voltage transformation ratio from the secondary side to the primary side of the isolation transformer. The value of this product is generally very small, so the actual output voltage of the converter is very small, that is, the withstand voltage requirement of the converter is low. Theoretically, a single H-bridge converter can meet the requirements, thus reducing the manufacturing cost.

[0071] To enable those skilled in the art to better understand the technical solution of this invention, the invention will be further described below with reference to a simulation example.

[0072] Build using Matlab / Simulink, such as Figure 3 The simulation model of the distribution network with 5 feeders shown has a phase-A ground fault set at the fault point. The simulation results are as follows. Figures 4-7 As shown.

[0073] Depend on Figure 4 It can be seen that the flexible fusion arc suppression device with phase power supply series voltage division proposed in this invention has a small residual current and good compensation effect when the ground fault transition resistance is 1Ω (representing metallic grounding).

[0074] Depend on Figure 5 It can be seen that the flexible fusion arc suppression device with phase power supply series voltage division proposed in this invention has a small fault residual current and a good compensation effect when the ground fault transition resistance is 100Ω.

[0075] Depend on Figure 6It can be seen that the flexible fusion arc suppression device with phase power supply series voltage division proposed in this invention has a small fault residual current and a good compensation effect when the ground fault transition resistance is 500Ω.

[0076] Depend on Figure 7 It can be seen that the flexible fusion arc suppression device with phase power supply series voltage division proposed in this invention has a small fault residual current and a good compensation effect when the ground fault transition resistance is 1000Ω.

[0077] This embodiment verifies the arc suppression effect of the flexible integrated arc suppression device with phase power supply series voltage division under different ground fault transition resistance conditions, and proposes a control algorithm suitable for this device structure: the phase power supply is controlled as a voltage source, the control target is the negative value of the fault phase power supply voltage, and the single-phase converter is controlled as a current source. The setpoint of the control target is obtained by multiplying the negative value of the fault phase power supply voltage, the system ground admittance, and the current ratio from the secondary side to the primary side of the isolation transformer. The proposed flexible integrated arc suppression device combines a passive (switch-on) arc suppression device and an active (converter) arc suppression device. The passive arc suppression device bears most of the arc suppression capacity, while the active arc suppression device bears a small portion of the arc suppression capacity, thus reducing the voltage and current withstand requirements of the converter and the overall manufacturing cost of the flexible arc suppression device. The proposed control algorithm of the flexible integrated arc suppression device integrates the voltage and current arc suppression principles, making up for the deficiency of voltage arc suppression methods in the case of low-resistance ground faults in terms of fault current compensation. It can effectively compensate for fault current under different ground fault transition resistance conditions, and has good engineering application value.

[0078] This patent is not limited to the above-described preferred embodiment. Anyone can derive other forms of flexible fusion arc suppression devices with phase power supply series voltage division under the guidance of this patent. All equivalent changes and modifications made within the scope of the claims of this invention shall fall within the scope of this patent.

Claims

1. A flexible and fused arc extinguishing device for series voltage division of a phase power supply, characterized by: The topology of the flexible fusion arc suppression device is a structure in which the phase power supply and the single-phase converter are connected in series after passing through an isolation transformer; the control algorithm of the flexible fusion arc suppression device is to control the phase power supply as a voltage source and the single-phase converter as a current source. The phase power supply is obtained by switching the secondary winding of the grounding transformer and stepping up the voltage through a step-up transformer; the single-phase converter is connected in series with the phase power supply after passing through an isolation transformer, or directly connected in series with the phase power supply; the DC power supply of the single-phase converter is provided by the secondary winding of the grounding transformer after rectification by a rectifier; the control target of the voltage source is the negative value of the fault phase power supply voltage; the setpoint of the control target of the current source is obtained by multiplying the negative value of the fault phase power supply voltage, the system ground admittance, and the current transformation ratio from the secondary side to the primary side of the isolation transformer. When a single-phase ground fault occurs in phase A, according to the arc suppression principle based on the phase power supply input, the following equation holds: （1） In the formula, The phase voltage of the faulty phase. For ground fault current, For ground fault transition resistance, This refers to the phase voltage of phase A in the distribution network. This refers to the voltage of phase A of the power distribution network. The neutral point voltage, This refers to the primary voltage of the step-up transformer. According to the principle of voltage arc suppression, if the primary voltage of the step-up transformer is controlled by switching the secondary side switch, the voltage of the step-up transformer can be reduced. Then, from equation (1), we can know that at this time... , This will enable arc suppression of grounding faults; the same principle applies to single-phase grounding faults in phases B and C. When a single-phase ground fault occurs in phase A, according to the current arc suppression principle based on the fully compensated current injected into the converter, the following equation holds: （2） In the formula, , , These are the three-phase ground currents of the distribution network. This refers to the primary current of a single-phase isolation transformer. For ground fault current, , , These are the three-phase power supply voltages of the distribution network. , , These are the three-phase phase voltages of the distribution network. The neutral point voltage, , , These are the three-phase-to-ground leakage resistances of the distribution network. , , Let be the equivalent capacitances of the three phases to ground in the distribution network; and let the turns ratio of the single-phase isolation transformer be... The output current of the single-phase converter ; According to the principle of arc suppression by electric current, let Then equation (2) can be transformed into （3） Equation (3) is the fundamental component of the compensation current, and the harmonic components of the compensation current can be obtained in the same way. According to the principle of current arc suppression, if the primary side current of a single-phase isolation transformer is controlled to be the ground fault full compensation current, and the full compensation current is the vector sum of the fundamental and harmonic components, and injected into the neutral point, the ground fault arc suppression can be achieved. set up , And there are Then equation (3) simplifies to （4） In the formula, , Therefore, the output current of the single-phase converter is determined to be... （5） The same applies to single-phase grounding faults in phases B and C.

2. The flexible fusion arc suppression device with phase power supply series voltage division according to claim 1, characterized in that: The single-phase converter is one of the following: two-level single-phase half-bridge / full-bridge, three-level single-phase half-bridge / full-bridge, multi-level single-phase half-bridge / full-bridge, or single-phase cascaded H-bridge.

3. The flexible fusion arc suppression device with phase power supply series voltage division according to claim 2, characterized in that: The rectifier is a single-phase controllable rectifier, a three-phase controllable rectifier, a single-phase uncontrollable rectifier, or a three-phase uncontrollable rectifier.

4. The flexible fusion arc suppression device with phase power supply series voltage division according to claim 3, characterized in that: The isolation transformer and the step-up transformer are two independent single-phase transformers or a combination of both.

5. The flexible fusion arc suppression device with phase power supply series voltage division according to claim 4, characterized in that: The flexible fusion arc extinguishing device specifically adopts the following control method: During normal operation, disconnect the switches on the secondary side of the single-phase step-up transformer and the secondary side of the single-phase isolation transformer to open the secondary side of the single-phase step-up transformer and the single-phase isolation transformer. This means that the phase power supply and the single-phase converter are taken out of operation. At this time, the distribution network operates in a neutral point non-effective grounding mode. During a ground fault, the phase of the input voltage on the secondary side of the single-phase step-up transformer is adjusted by changing the state of the switch, thereby making the phase power supply voltage negative of the fault phase power supply voltage and feeding it into the neutral point of the distribution network, using a voltage arc suppression method. Then close the switch on the secondary side of the single-phase isolation transformer, and control the current injected by the single-phase converter into the neutral point of the distribution network through the single-phase isolation transformer to be the full compensation current for the ground fault. Its value is the product of the negative value of the fault phase power supply voltage and the total ground admittance of the distribution network. The current arc extinguishing method is adopted, and the two are combined to form a voltage and current fusion arc extinguishing method.

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