A power distribution network arc extinction method and system based on distributed power electronic device cooperation

Abstract

This invention discloses a method and system for arc suppression in distribution networks using distributed power electronic equipment in coordination. The method includes... n Distributed installation on the feeder of the distribution network i A power electronic device is connected to the medium-voltage side of the distribution network via a power electronic converter and then connected to the distribution network's ground loop via a zero-sequence channel. When the distribution network is in steady-state operation and there is a three-phase ground parameter imbalance, at least one power electronic device is controlled to output a compensation current into the distribution network. When a single-phase ground fault occurs, it will... i The power electronic equipment is grouped into a current support group and a voltage clamping unit, which switch to current arc suppression mode and voltage clamping mode respectively. When the single-phase ground fault disappears, the power electronic equipment exits the coordinated arc suppression mode and switches back to steady-state operation mode. This invention achieves stable and reliable suppression of arcs from single-phase ground faults.

Description

Technical Field

[0001] This invention relates to the field of distribution network fault protection and flexible control technology, specifically to a distribution network arc suppression method and system using distributed power electronic equipment in coordination. Background Technology

[0002] With the advancement of new power system construction, the penetration rate of photovoltaic inverters, energy storage converters, power routers, static synchronous compensators, and various power electronic equipment in distribution networks is continuously increasing. Distribution networks are gradually evolving from traditional passive networks to active networks containing a large number of power electronic devices. At the same time, single-phase grounding faults remain the most frequent type of fault in distribution networks. The electric arcs they generate can cause overvoltages, equipment burnout, and even fires, seriously threatening power grid safety and personal safety.

[0003] Traditional arc suppression methods mainly rely on arc suppression coils or centralized active arc suppression devices. Arc suppression coils can only compensate for capacitive currents in ground faults, and their ability to suppress active components and transient processes generated by leakage resistance is limited. Significant residual currents and voltages often remain at the fault point, making reliable arc extinguishing difficult. While centralized active arc suppression devices can achieve full compensation, they require capacity configuration based on the maximum ground capacitance current of the entire network, resulting in large equipment size, high cost, and low utilization due to being idle for most of the normal operating time. On the other hand, the power electronic equipment widely deployed in the distribution network possesses controllable voltage and current output capabilities and has a certain capacity margin under most operating conditions. If flexible grounding capabilities can be provided without affecting their original grid connection functions, allowing them to participate in fault arc suppression when needed, the need for additional dedicated arc suppression devices can be avoided, significantly reducing system construction costs.

[0004] However, the capacity of a single power electronic device is usually limited. If a single device undertakes all the arc suppression tasks, it can easily lead to overload and affect the safe operation of its original functions. Existing distributed arc suppression schemes often focus on modeling multiple devices and proposing a zero-sequence network architecture, allowing each device to jointly undertake the zero-sequence compensation task. However, these schemes typically require complex power coordination mechanisms and struggle to meet the different needs of steady-state operation and fault stages, resulting in complex control and high system coupling in engineering implementation. Therefore, a new technical approach is urgently needed. This approach, while fully utilizing existing power electronic devices, should adopt a method closer to physical mechanisms, enabling different devices to assume different roles during faults. This would achieve highly reliable collaborative arc suppression with lower control complexity, while simultaneously reusing the devices during the steady-state stage to improve the operational quality of the distribution network. Summary of the Invention

[0005] This invention proposes a distribution network arc suppression method and system using distributed power electronic equipment in coordination, which solves the problems in the prior art where a single device undertaking all arc suppression tasks is prone to overload and difficult to simultaneously meet the requirements of steady-state asymmetric compensation and fault arc suppression.

[0006] To address the aforementioned technical problems, this invention provides a method for arc suppression in a distribution network using distributed power electronic equipment in coordination, comprising the following steps: exist n Distributed installation on the feeder of the distribution network i Taiwan power electronic equipment, among which The power electronic equipment is connected to the medium-voltage side of the distribution network via a power electronic converter and is connected to the distribution network ground loop via a zero-sequence channel; When the distribution network is in steady-state operation and there is asymmetry in the three-phase ground parameters, control i At least one of the power electronic devices injects zero-sequence compensation current into the distribution network to suppress the neutral point zero-sequence voltage offset to below a preset threshold. When a single-phase ground fault occurs, i Taiwan's power electronic equipment is grouped into current support units and voltage clamping units, among which... i -1 is a current support group, the one closest to the busbar. The platform is a voltage clamping unit. The current support group is controlled to switch to the current arc suppression mode and inject zero-sequence compensation current; the voltage clamping unit is controlled to switch to the voltage clamping mode and establish a fault phase voltage reference; when the single-phase ground fault disappears, the power electronic equipment is controlled to exit the collaborative arc suppression mode and switch back to the steady-state operation mode.

[0007] Preferably, controlling the current support group to switch to the current arc suppression mode and injecting zero-sequence compensation current includes the following steps: Introducing current distribution coefficient k , The current distribution coefficient k The ratio of the output current of the current support group to the compensation current required by the distribution network; When the arc suppression coil is engaged, the compensation current required by the distribution network is the difference between the compensation current of the total capacitance current to ground and the compensation current of the arc suppression coil. When the arc suppression coil is not engaged, the required compensation current for the distribution network is the total system-to-ground capacitance current; each power electronic device in the current support group is configured according to... The required compensation current for the power distribution network is the zero-sequence compensation current output. By adjusting the current distribution coefficient k Change the arc suppression capacity ratio between the current support group and the voltage clamping unit.

[0008] Preferably, when the arc suppression coil is engaged, the output current of the current support group is... satisfy: ； in This represents the effective value of the power supply voltage of the faulty phase in the distribution network. The fundamental angular frequency of the power grid; The total zero-sequence capacitance of the three phases to ground in the distribution network; For arc suppression coil inductance; When the arc suppression coil is not engaged, the output current of the current support group is... satisfy: .

[0009] Preferably, the voltage clamping unit uses the opposite of the fault phase power supply voltage as the voltage reference command, and outputs the remaining capacitor current and all active leakage current that are not compensated by the current support group through voltage closed-loop control, thereby clamping the residual voltage at the fault point below the preset arc extinguishing threshold.

[0010] Preferably, the current distribution coefficient k The value of is determined based on the rated capacity and real-time remaining capacity of the power electronic equipment in the voltage clamping unit; with the current distribution coefficient k As the current increases, the power demand of the current support group rises, while the power demand of the voltage clamping unit decreases.

[0011] Preferably, the control structure of the current arc suppression mode includes: establishing a zero-sequence current closed-loop control circuit, inputting the difference between the zero-sequence current reference value and the actual output current into a proportional resonant controller, wherein the resonant frequency of the proportional resonant controller is set at the power frequency fundamental frequency, and the output of the proportional resonant controller serves as the modulation command of the power electronic converter.

[0012] Preferably, the control structure of the voltage clamping mode includes: inputting the difference between the fault phase voltage reference command and the measured zero-sequence voltage into a proportional repetitive controller, wherein the proportional repetitive controller is composed of a repetitive control branch and a proportional control branch connected in parallel; the repetitive control branch includes a delay element, a filtering compensation element, and a gain coefficient based on the internal mode principle, generating a periodic high-gain output at the fundamental frequency and harmonics; the outputs of the repetitive control branch and the proportional control branch are superimposed as the modulation command of the power electronic converter.

[0013] Preferably, the control i At least one of the power electronic devices injects zero-sequence compensation current into the distribution network, including the following steps: based on the measured three-phase ground admittance parameters , , The reference value of the compensation current is calculated according to the following formula. : ； in The voltage electromotive force of phase A; The rotation factor; The compensation current reference value The difference between the current and the actual output current is input to a proportional resonant controller, which outputs a modulation command to drive the power electronic device to inject the zero-sequence compensation current into the distribution network.

[0014] Preferably, the i The coordination methods among the power electronic devices include: under conditions without communication, each power electronic device switches to the current support group or the voltage clamping unit based on locally collected zero-sequence voltage and zero-sequence current information and according to preset criteria; under conditions with communication, the central controller issues grouping instructions and working mode switching instructions to each power electronic device according to the capacity margin, node position and operating status of each power electronic device.

[0015] The present invention also provides a distribution network arc suppression system with distributed power electronic equipment in coordination, the system being configured to perform the above-described distribution network arc suppression method with distributed power electronic equipment in coordination, comprising: n Distribution network feeders; distributed installations in n On the feeder of the distribution network i Taiwan power electronic equipment, among which The power electronic equipment is connected to the medium-voltage side of the distribution network via a power electronic converter and connected to the distribution network ground circuit via a zero-sequence channel. The power electronic equipment includes at least one of the following: a power router with flexible grounding function, a solid-state transformer, a static synchronous compensator, a unified power quality regulator, or a smart soft switch.

[0016] The advantages of this invention include at least the following: 1. By grouping distributed power electronic devices into current support groups and voltage clamping units, and switching them to current arc suppression mode and voltage clamping mode respectively, the physical division of labor and coordination between fault energy transfer and voltage support is realized. This reduces the capacity requirement of a single device and ensures effective transfer of fault current and reliable clamping of fault point voltage. 2. By introducing a current distribution coefficient, the problem of rationally allocating compensation capacity among multiple devices during the coordinated arc suppression process is solved. The task ratio between the current support group and the voltage clamping unit can be flexibly adjusted according to the device capacity and location conditions, avoiding single-machine overload and improving the system's adaptability to different configuration scenarios and the utilization rate of the equipment. 3. It endows conventional grid-connected equipment such as power routers and unified power quality regulators with flexible grounding capabilities, enabling them to achieve fault arc suppression without the need for additional arc suppression devices. The system can dynamically group equipment according to its real-time capacity margin and location, greatly improving asset utilization and grid operation flexibility. 4. It not only covers steady-state asymmetric governance and transient fault arc suppression, but also clarifies the exit mechanism after the fault disappears. Whether it is centralized control under communication conditions or autonomous coordination under non-communication conditions, it can ensure the safe and stable operation of the distribution network throughout the entire process. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the topology of the arc suppression system for distribution networks based on the cooperation of distributed power electronic devices as described in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram showing the curve relationship between the power requirements of the current support group and the voltage clamping unit and the current distribution coefficient k in Embodiment 2 of the present invention. Figure 3 This is a flowchart of the collaborative control logic of the system described in Embodiment 2 of the present invention under steady-state and fault states; Figure 4 This is a schematic diagram of the control structure of the current support group described in Embodiment 2 of the present invention; Figure 5 This is a schematic diagram of the control structure of the voltage clamping unit described in Embodiment 2 of the present invention; Figure 6 This is a simulation waveform diagram of the steady-state asymmetric compensation effect of the ungrounded system in Embodiment 3 of the present invention; Figure 7 This is a schematic diagram of the simulation waveform of the fault-coordinated arc extinguishing process in the ungrounded system in Embodiment 3 of the present invention; Figure 8 This is a schematic diagram of the simulated waveform of the fault-coordinated arc extinguishing process of the resonant grounding system in Embodiment 3 of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0019] Example 1 like Figure 1 As shown, this embodiment of the invention provides a distribution network arc suppression system with distributed power electronic equipment cooperation, including a distribution network. nfeeder and distributed setup in n On the feeder line i Taiwan power electronic equipment, among which Power electronic equipment is connected to the medium-voltage side of the distribution network via a power electronic converter and is connected to the distribution network ground loop via a zero-sequence channel.

[0020] In this embodiment of the invention, the power electronic device is preferably a power router with flexible grounding function. As other optional embodiments, the power electronic device can also be a solid-state transformer, a static synchronous compensator, a unified power quality regulator, or a smart soft switch. All of the above-mentioned power electronic devices are connected to the medium-voltage side of the distribution network via power electronic converters, possessing zero-sequence controllable current source output characteristics and zero-sequence controllable voltage source output characteristics, enabling active regulation of the zero-sequence current and fault phase voltage of the distribution network.

[0021] The power distribution network fault arc suppression system of this embodiment is configured to execute the following control logic at different operating stages: During the steady-state operation of the distribution network, at least one power electronic device is controlled to inject compensation current into the distribution network to actively compensate for the asymmetry of the distribution network's ground parameters, thereby suppressing the neutral point zero-sequence voltage offset to below a preset threshold. Specifically, due to insufficient transposition of distribution network lines or uneven distribution of single-phase loads, the three-phase ground admittance is often unbalanced. Each power electronic device collects voltage and current data of its node in real time, and the internal controller calculates the zero-sequence voltage offset of the current line in real time based on Kirchhoff's current law, and outputs the zero-sequence compensation current required to compensate for the unbalanced ground parameters based on the calculation results.

[0022] When a single-phase ground fault occurs in the distribution network, according to the preset coordination strategy, the following will be implemented: i Taiwan's power electronic equipment is divided into two categories and switches between operating modes. The first category, the current support assembly, comprises... i -1 unit, switched to current arc suppression mode, acts as a current support unit to output zero-sequence compensation current to the distribution network, in order to share and transfer fault current. The second type of power electronic equipment, namely the voltage clamping unit, is the first unit installed closest to the busbar. Taiwan, among which The system switches to voltage clamping mode, establishing a voltage reference for the fault phase as a voltage clamping unit, and clamping the residual voltage at the fault point below a preset arc-extinguishing threshold. Thus, through the synergistic effect of the current support unit and the voltage clamping unit at the physical level, rapid arc extinguishing of a single-phase ground fault is achieved.

[0023] This invention supports flexible collaboration methods. When the aforementioned power electronic devices have a communication network, tasks can be dynamically allocated based on network-wide information through a central controller. When communication is restricted, each power electronic device can autonomously switch to either the first type of device (current support group) or the second type of device (voltage clamping unit) according to preset logic based on locally collected voltage and current information, achieving autonomous coordination under conditions of no communication.

[0024] In this embodiment of the invention, to achieve a reasonable allocation of arc suppression tasks among different power electronic devices, the system incorporates a capacity coordination allocation strategy. Specifically, a current allocation coefficient is introduced. k ,in This is defined as the proportion of compensation current borne by the current support group. When the arc suppression coil is engaged, the compensation current required by the distribution network is the difference between the compensation current of the total capacitance current to ground and the compensation current of the arc suppression coil. When the arc suppression coil is not engaged, the compensation current required by the distribution network is the total capacitance current to ground of the system.

[0025] Output current of the current support group The following relationship must be satisfied when the arc suppression coil is engaged: ; When the arc suppression coil is not engaged: ; Where, ∑ This refers to the total zero-sequence capacitance of the three-phase ground of the distribution network.

[0026] The output amplitude of the power electronic equipment of the control current support group is k The system requires compensation current multiple times, and i -1 current support group, each power electronic device is based on k Divide by i -1 times the required system compensation current outputs zero-sequence compensation current. The power electronic equipment controlling the voltage clamping unit automatically outputs the remaining compensation current and maintains voltage clamping through voltage closed-loop control. This is achieved by adjusting the current distribution coefficient. k This enables the allocation of arc suppression capacity among different power electronic devices.

[0027] To quantitatively assess the capacity occupancy of various power electronic devices when performing arc suppression tasks, this embodiment of the invention constructs a refined capacity calculation model based on the internal parameters of the devices. Taking a power router as an example, the power requirements of its current support group (the first type of device) and voltage clamping unit (the second type of device) can be calculated using the following formulas.

[0028] When the arc suppression coil is engaged, the power demand of the current support group is as follows: for: ; Power requirements of voltage clamping unit for: ; When the arc suppression coil is not engaged, the power demand of the current support group is as follows: for: ; Power requirements of voltage clamping unit for: ; in, ω represents the effective value of the power supply voltage of the faulted phase in the distribution network; ω represents the fundamental angular frequency of the power grid; ∑ The total zero-sequence capacitance of the three-phase-to-ground distribution network; ∑ The total zero-sequence leakage resistance of the three phases to ground in the distribution network; For arc suppression coil inductance; This is the current distribution coefficient; and These are the equivalent damping resistance and supporting capacitor parameters on the DC side of the power router.

[0029] like Figure 2 As shown, taking an ungrounded system without an arc suppression coil as an example, substituting the power distribution network simulation parameters set in this embodiment of the invention into the above formula yields the following results. and With coefficient k The changing curve relationship. As can be seen from the graph, with... k As the value increases, the capacity requirement of the current support unit rises, while the capacity requirement of the voltage clamping unit decreases. Based on this relationship and the actual remaining capacity of each device, the system selects different... k Value, of which k The value is selected based on the equipment capacity of the voltage clamping unit and ensures that the equipment does not experience overcurrent, so as to achieve a reasonable distribution of arc suppression tasks among different equipment and avoid single-machine overload.

[0030] During normal grid-connected operation, each power electronic device operates in a conventional control mode that conforms to its own characteristics. For example, the power router and solid-state transformer can operate in PQ mode or VdcQ mode, the static synchronous compensator operates in reactive power regulation mode, and active ground parameter compensation control commands are superimposed on this. When a single-phase ground fault occurs in the distribution network, it switches to the coordinated arc suppression control state.

[0031] After a single-phase ground fault disappears, the system continuously monitors the grid insulation status. When the insulation at the fault point is detected to have recovered and the current has decreased significantly, the system controls the power electronic equipment to exit the coordinated arc suppression mode and smoothly switch back to the steady-state operation mode or their original grid-connected operation state to ensure the continuity and stability of the distribution network operation.

[0032] Example 2 like Figure 3 As shown, this embodiment of the invention takes an electric power router as an example to describe in detail the collaborative control method of the power distribution network fault arc suppression system under different operating conditions, specifically including the following stages.

[0033] The first stage is the steady-state operation stage. During normal operation of the distribution network, each power router collects voltage and current data of its local node in real time. Due to insufficient line transposition or uneven distribution of single-phase loads, the three-phase ground admittance of the distribution network is often unbalanced. The internal controller of the power router calculates the zero-sequence voltage offset of the current line in real time based on Kirchhoff's current law. Each power router performs compensation for the unbalanced ground parameters according to the calculation results.

[0034] The method for compensating the ground parameters of the line to which the power router is located is as follows. The control core of the power router is based on the admittance balance principle, calculating the reference value of the required injected compensation current. Specifically, based on the measured three-phase ground admittance parameters, the compensation current reference value is... The following relationship must be satisfied: ; in, The voltage electromotive force of phase A; , , These are the three-phase admittances; a is the rotation factor.

[0035] like Figure 4 As shown, the power router of the current support group acts as a compensation device in steady state, establishing a current closed-loop control. It utilizes a proportional resonant controller to track the compensation current command without steady-state error, driving the power router to actively inject current into the grid. Through this step, the neutral point voltage of the distribution network is dynamically clamped near zero potential.

[0036] The second phase is fault detection and mode switching. When the system detects a single-phase ground fault, such as detecting an excessive zero-sequence voltage, it immediately initiates a coordinated arc suppression strategy. The system then switches modes according to the preset coordinated strategy. i Taiwan's power electronic equipment is grouped into two categories. The first category consists of current support units, which switch to current arc suppression mode and function as current support units. The second category consists of voltage clamping units, which switch to voltage clamping mode and function as voltage clamping units.

[0037] The third stage is the coordinated arc suppression stage. The current support unit outputs the set zero-sequence compensation current, i.e. k This unit doubles the compensation current required by the system. During the arc suppression phase, this unit continues to use... Figure 4The control structure shown employs a proportional-resonant control strategy. Its control structure establishes a zero-sequence current closed-loop control circuit, inputting the difference between the zero-sequence current reference value and the actual output current into the proportional-resonant controller. The resonant frequency of the proportional-resonant controller is set at the fundamental power frequency, i.e., 50Hz, and its output serves as the modulation command for the power electronic converter. Since the fault current is a power frequency AC signal, traditional proportional-integral controllers suffer from phase lag and steady-state error. However, the proportional-resonant controller has infinite gain at its resonant frequency, enabling zero steady-state error tracking of the AC reference signal. This ensures the accuracy of the current support group's output current and effectively undertakes most of the fault current transfer task.

[0038] The voltage clamping unit is then activated. Using the negative of the fault phase power supply voltage as a reference command, this unit establishes rigid voltage support and executes voltage arc suppression control, forcibly clamping the residual voltage at the fault point below a preset arc suppression threshold, thus controlling the fault phase voltage to approach zero. During this process, the unit utilizes the voltage closed-loop characteristic to automatically output the remaining compensation current, which includes the residual capacitive current not compensated by the current support group and all active power leakage current, thereby achieving precise and full compensation for the fault residual current.

[0039] This unit employs a proportional repetition control strategy, such as... Figure 5 As shown. The controller includes a proportional branch and a repetitive control branch connected in parallel. The repetitive control branch includes a delay element based on the internal model principle. Filtering and compensation stage S Gain coefficient and internal stabilizing filter Q It provides significant gain at the fundamental frequency and its harmonics, enabling zero steady-state error tracking of the periodic reference signal. This effectively suppresses background harmonics in the distribution network, ensuring that the residual voltage at the fault point is strictly limited below the arc-extinguishing threshold. The gain coefficient of the proportional branch is... It provides a fast dynamic response to improve the response speed to fault transient processes. The outputs of the repetitive control branch and the proportional branch are superimposed and used together as the modulation command of the power electronic converter to achieve zero steady-state error clamping control of the residual voltage at the fault point.

[0040] The fourth stage is the fault recovery and exit stage. During the arc suppression process, the system continuously monitors the grid insulation status. When a single-phase ground fault is detected to have disappeared, for example, when the insulation at the fault point is restored and the current drops significantly, the system controls the power electronic equipment to exit the coordinated arc suppression mode and smoothly switch back to the steady-state operation mode or their original grid-connected operation state to ensure the continuity and stability of the distribution network operation.

[0041] Example 3 This invention provides verification results based on a simulation platform to further illustrate the effectiveness of the embodiments. The simulation conditions are set as follows: a 10kV distribution network model including multiple feeders and two distributed power routers is constructed, with the two devices denoted as Device 1 and Device 2. The simulation is divided into two operating conditions: an ungrounded system and a resonant grounded system. Key simulation parameters are set as follows: the total three-phase-to-ground capacitance ∑ of the distribution network. The value is 19.578μF, which is the equivalent damping resistance on the DC side of the power router. The value is 50Ω, which is the DC-side support capacitor for the power router. The value is set to 1000μF, the arc suppression coil inductance L is 1H, and it operates in undercompensated mode. Steady-state asymmetrical compensation is activated at 0.3s, a single-phase ground fault occurs at 0.5s, the current support unit (equipment 1) is activated at 0.6s, and the voltage clamping unit (equipment 2) is activated at 0.7s. The current distribution coefficient k is selected as 0.75, and the transition resistance is 100Ω.

[0042] The simulation results are analyzed as follows: Simulation results of ungrounded system are as follows Figure 6 and Figure 7 As shown. During the normal operation phase from 0.0s to 0.3s, the system is in a natural operating state. Due to the asymmetry of ground parameters, there is a relatively high zero-sequence voltage of approximately 400V at the neutral point. During the steady-state compensation phase from 0.3s to 0.5s, after the active ground parameter compensation control is activated, device 1 injects a compensation current of approximately 0.9A, and the neutral point voltage rapidly drops to approximately 15V, verifying the effectiveness of the steady-state imbalance mitigation.

[0043] During the fault occurrence phase (0.5s to 0.6s), a single-phase ground fault occurred in phase A, causing a momentary voltage drop at the fault point, accompanied by a large short-circuit current. The effective value of the fault current was approximately 34.01A. During the current support activation phase (0.6s to 0.7s), device 1 switched to current arc suppression mode and began operation, outputting approximately 80% of the ground capacitance current, with an effective value of approximately 29.52A. At this time, the fault current was significantly reduced, but the residual voltage at the fault point was not completely eliminated. After 0.7s, device 2 switched to voltage clamping mode and began operation, with an effective value of approximately 8.96A injected. Figure 7 As can be seen, after device 2 is put into operation, the residual voltage at the fault point is quickly and forcibly clamped below the arc extinguishing threshold, and the effective value of the fault current drops to approximately 0.22A. Through the above-mentioned timing control, the coordinated control capability of the embodiment of the present invention at different stages is verified, the fault arc is reliably extinguished, and the voltage of the non-faulty phase does not exhibit excessively high transient impacts.

[0044] Simulation results of the resonant grounding system are as follows Figure 8As shown. Under this operating condition, the arc suppression coil provides partial capacitive current compensation, with an effective value of approximately 18.8A. The current support group and voltage clamping unit only need to compensate for the residual current after arc suppression coil compensation. When a fault occurs, the effective value of the fault current is approximately 20.6A. After device 1 is put into operation, the effective value of the output injected current is approximately 14.2A. After device 2 is put into operation, the effective value of the output injected current is approximately 5.5A, and the effective value of the fault current drops to approximately 0.45A. Simulation results show that, under the condition of arc suppression coil operation, the collaborative arc suppression method of this embodiment can also effectively transfer the fault current to the power electronic equipment and clamp the residual voltage at the fault point below the arc extinguishing threshold, achieving reliable extinction of the fault arc.

[0045] In summary, this invention, through physical-level coordination of power electronic devices, achieves both active compensation for parameter asymmetry during steady-state operation and rapid arc suppression of single-phase ground faults during fault operation. Compared to traditional single-device systems, this system effectively reduces the capacity requirements of individual units and improves the operational reliability of the distribution network.

[0046] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; only preferred embodiments of the present invention are illustrated. The descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. As long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification.

[0047] It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the appended claims.

Claims

1. A method for arc suppression in a distribution network using distributed power electronic equipment in coordination, characterized in that, Includes the following steps: exist n Distributed installation on the feeder of the distribution network i Taiwan power electronic equipment, among which The power electronic equipment is connected to the medium-voltage side of the distribution network via a power electronic converter and is connected to the distribution network ground loop via a zero-sequence channel; When the distribution network is in steady-state operation and there is asymmetry in the three-phase ground parameters, control i At least one of the power electronic devices injects zero-sequence compensation current into the distribution network to suppress the neutral point zero-sequence voltage offset to below a preset threshold. When a single-phase ground fault occurs, i Taiwan's power electronic equipment is grouped into current support units and voltage clamping units, among which... i -1 is a current support group, the one closest to the busbar. The platform is a voltage clamping unit. Control the current support group to switch to current arc suppression mode and inject zero-sequence compensation current; control the voltage clamping unit to switch to voltage clamping mode and establish fault phase voltage reference. Once the single-phase ground fault disappears, the power electronic equipment is controlled to exit the collaborative arc suppression mode and switch back to the steady-state operation mode.

2. The arc suppression method for a distribution network using distributed power electronic equipment in coordination according to claim 1, characterized in that: Controlling the current support group to switch to current arc suppression mode and injecting zero-sequence compensation current includes the following steps: Introducing current distribution coefficient k , The current distribution coefficient k The ratio of the output current of the current support group to the compensation current required by the distribution network; When the arc suppression coil is engaged, the compensation current required by the distribution network is the difference between the compensation current of the total capacitance current to ground and the compensation current of the arc suppression coil. When the arc suppression coil is not engaged, the required compensation current for the distribution network is the total system-to-ground capacitance current; each power electronic device in the current support group is configured according to... The required compensation current for the power distribution network is the zero-sequence compensation current output. By adjusting the current distribution coefficient k Change the arc suppression capacity ratio between the current support group and the voltage clamping unit.

3. The arc suppression method for a distribution network using distributed power electronic equipment in coordination according to claim 2, characterized in that: When the arc suppression coil is engaged, the output current of the current support group is... satisfy: ； in This represents the effective value of the power supply voltage of the faulty phase in the distribution network. The fundamental angular frequency of the power grid; The total zero-sequence capacitance of the three phases to ground in the distribution network; For arc suppression coil inductance; The imaginary unit; When the arc suppression coil is not engaged, the output current of the current support group is... satisfy: 。 4. The arc suppression method for a distribution network using distributed power electronic equipment in coordination according to claim 2, characterized in that: The voltage clamping unit uses the opposite of the fault phase power supply voltage as the voltage reference command, and outputs the remaining capacitor current and all active leakage current that are not compensated by the current support group through voltage closed-loop control, thereby clamping the residual voltage at the fault point below the preset arc extinguishing threshold.

5. The arc suppression method for a distribution network using distributed power electronic equipment in coordination according to claim 2, characterized in that: The current distribution coefficient k The value of is determined based on the rated capacity and real-time remaining capacity of the power electronic equipment in the voltage clamping unit; with the current distribution coefficient k As the current increases, the power demand of the current support group rises, while the power demand of the voltage clamping unit decreases.

6. The arc suppression method for a distribution network using distributed power electronic equipment in coordination according to claim 1, characterized in that: The control structure of the current arc suppression mode includes: establishing a zero-sequence current closed-loop control circuit, inputting the difference between the zero-sequence current reference value and the actual output current into a proportional resonant controller, the resonant frequency of the proportional resonant controller being set at the power frequency fundamental frequency, and the output of the proportional resonant controller serving as the modulation command of the power electronic converter.

7. The arc suppression method for a distribution network using distributed power electronic equipment in coordination according to claim 1, characterized in that: The control structure of the voltage clamping mode includes: inputting the difference between the fault phase voltage reference command and the measured zero-sequence voltage into a proportional repetitive controller, which is composed of a repetitive control branch and a proportional control branch connected in parallel; the repetitive control branch includes a delay element, a filtering compensation element, and a gain coefficient based on the internal mode principle, generating a periodic high-gain output at the fundamental frequency and harmonics; the outputs of the repetitive control branch and the proportional control branch are superimposed as the modulation command of the power electronic converter.

8. The arc suppression method for a distribution network using distributed power electronic equipment in coordination according to claim 1, characterized in that: The control i At least one of the power electronic devices injects zero-sequence compensation current into the distribution network, including the following steps: based on the measured three-phase ground admittance parameters , , The reference value of the compensation current is calculated according to the following formula. : ； in The voltage electromotive force of phase A; It is the rotation factor; The compensation current reference value The difference between the current and the actual output current is input to a proportional resonant controller, which outputs a modulation command to drive the power electronic device to inject the zero-sequence compensation current into the distribution network.

9. The arc suppression method for a distribution network using distributed power electronic equipment in coordination according to claim 1, characterized in that: The i The coordination methods among the power electronic devices include: under conditions without communication, each power electronic device switches to the current support group or the voltage clamping unit based on locally collected zero-sequence voltage and zero-sequence current information and according to preset criteria; under conditions with communication, the central controller issues grouping instructions and working mode switching instructions to each power electronic device according to the capacity margin, node position and operating status of each power electronic device.

10. A distribution network arc suppression system with distributed power electronic equipment in coordination, the system being configured to perform a distribution network arc suppression method with distributed power electronic equipment in coordination as described in any one of claims 1-9, characterized in that, include: n Distribution network feeders; distributed installations in n On the feeder of the distribution network i Taiwan power electronic equipment, among which The power electronic equipment is connected to the medium-voltage side of the distribution network via a power electronic converter and connected to the distribution network ground circuit via a zero-sequence channel. The power electronic equipment includes at least one of the following: a power router with flexible grounding function, a solid-state transformer, a static synchronous compensator, a unified power quality regulator, or a smart soft switch.

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