Multi-terminal arc suppression coil cooperative control method and system based on neutral point flexible grounding

Abstract

The invention relates to a multi-terminal arc suppression coil cooperative control method based on neutral point flexible grounding, and the method comprises the steps: a control host sends a compensation amount to a grounding transformer arc suppression coil host, and a control slave sends the compensation amount to each grounding transformer arc suppression coil slave; fault detection and phase selection; closed-loop control based on voltage; fault judgment: if the zero-sequence voltage of the system is reduced, judging that the fault is a single-phase instantaneous grounding fault; and if the zero sequence voltage of the system still exceeds 20% of the phase voltage after the injection of the neutral point current is stopped, determining that the fault is a permanent fault. A hierarchical cooperative control architecture is adopted, a master-slave mode is adopted, a control host of an arc suppression coil of a system substation serves as a master controller, a control slave of an arc suppression coil of a new energy plant station serves as slave equipment, and network plant arc suppression coil cooperative compensation is achieved through an optical fiber communication network; accurate supplement is carried out on the arc suppression coil, power frequency and active components are fully compensated, and 100% arc suppression is realized; the current injected into the neutral point of the flexible grounding device is dynamically adjusted, and the inductive and capacitive modes are automatically switched.

Description

Technical Field

[0001] This invention relates to the field of new energy power system technology, and in particular to a method and system for coordinated control of multi-terminal arc suppression coils based on neutral point flexible grounding. Background Technology

[0002] Currently, the proportion of renewable energy sources such as wind power and photovoltaics in the power distribution network has increased significantly, with a large number of new energy power plants directly connected to the 10kV / 35kV system. The widespread integration of new energy sources has changed the traditional structure of the power distribution network, bringing new challenges to grounding fault handling: medium-voltage power distribution networks typically use neutral point arc suppression coil grounding. When the new energy power plant and the distribution network line are on the same busbar, in order to ensure the reliability of the power supply of the distribution network line, the neutral point grounding method of the new energy power plant should be consistent with the grid, that is, to use an arc suppression coil. The capacity of the arc suppression coil should be sufficient to compensate for the single-phase grounding capacitance current of its own collector line.

[0003] Both the substations and new energy power plants in the system are equipped with arc suppression coils, forming a multi-point distributed compensation pattern. When a single-phase ground fault occurs, each arc suppression coil operates independently. Due to the lack of coordinated control, the total compensation current may be excessive or insufficient, leading to overcompensation (neutral point voltage reverses, non-faulty phase voltage spikes) or undercompensation (excessive residual current, arc reignition, and limited arc extinguishing success rate). In addition, the intermittent nature of new energy power generation causes frequent changes in system ground parameters. Traditional arc suppression coils cannot compensate for active and harmonic currents, and their high-resistance ground fault detection capability is insufficient (only below 500Ω), easily causing accidents such as electric shock and electrical fires.

[0004] In existing technologies, flexible grounding schemes using parallel and arc-suppression coils control the fault point voltage by injecting zero-sequence current through a PWM inverter. However, these schemes primarily focus on single-point compensation and fail to address the issue of multi-point coordination. Therefore, there is an urgent need for a flexible grounding control system capable of coordinating multiple arc-suppression devices and achieving precise voltage regulation and dynamic compensation. Summary of the Invention

[0005] To address the issue that existing technologies often focus on single-point compensation and fail to address multi-point coordination, the present invention aims to provide a multi-terminal arc suppression coil coordinated control method based on neutral point flexible grounding, which employs a hierarchical coordinated control architecture to achieve coordinated compensation of grid and plant arc suppression coils.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a multi-terminal arc suppression coil coordinated control method based on neutral point flexible grounding, the method comprising the following sequential steps:

[0007] (1) Coordinated compensation allocation: The control host allocates the compensation coefficients of the grounding transformer arc suppression coil master and each grounding transformer arc suppression coil slave; the control host sends the arc suppression coil compensation amount to the control slave through the optical fiber communication network; the control host sends the compensation amount to the grounding transformer arc suppression coil master, and the control slave sends the compensation amount to each grounding transformer arc suppression coil slave; each grounding transformer arc suppression coil adjusts its gear according to the compensation amount and carries out pre-adjustment compensation;

[0008] (2) Fault detection and phase selection: The control host monitors the zero-sequence voltage of the system in real time. When the zero-sequence voltage exceeds 20% of the phase voltage, it is determined that a ground fault has occurred. Then, the amplitude of the three-phase voltage is compared to determine that the lowest phase is the faulty phase.

[0009] (3) Voltage-based closed-loop control: At the initial moment of a fault, the host controller controls the flexible grounding device to inject neutral point current. The closed-loop control mode is adopted, and the voltage of the fault relative to ground is used as the feedback input. The injected neutral point current is adjusted to make the voltage of the fault relative to ground 0. The injection time of the neutral point current is set to 10s.

[0010] (4) Fault identification: After the neutral point current is injected for 10 seconds, the injected neutral point current value is reduced. If the zero-sequence voltage of the system drops, it is determined to be a single-phase instantaneous ground fault; if the zero-sequence voltage of the system still exceeds 20% of the phase voltage after the neutral point current is stopped, it is determined to be a permanent fault.

[0011] Step (1) specifically refers to: the control host calculating the provisional value of the low-voltage system's capacitance to ground on a 24-hour cycle. Provisional estimate of single-phase ground capacitance current and corresponding system compensation amount ;

[0012] Provisional estimate of single-phase ground capacitance current for:

[0013] ;

[0014] In the formula, It is the rated voltage of the low-voltage system. It is angular velocity;

[0015] Corresponding system compensation amount for:

[0016] ;

[0017] The control host allocates the compensation coefficient of the grounding transformer arc suppression coil host. Compensation coefficients of each grounding transformer arc suppression coil slave unit The compensation current of the grounding transformer arc suppression coil main unit of the system station for:

[0018] ;

[0019] According to the compensation coefficient Setting host inductive impedance and host compensation amount Among them, host inductive impedance for:

[0020] ;

[0021] Host compensation amount for:

[0022] ;

[0023] Compensation current of the slave unit of the grounding transformer arc suppression coil in each new energy power plant for:

[0024] ;

[0025] According to the compensation coefficient Setting the slave sensor resistance and corresponding slave compensation amount Among them, from machine-sensory resistance for:

[0026] ;

[0027] Slave compensation amount for:

[0028] ;

[0029] The control host sends slave compensation values ​​to the control slave via a fiber optic communication network every 24 hours. The control host and control slave respectively send the host compensation amount to the grounding transformer arc suppression coil host and the grounding transformer arc suppression coil slave. Slave compensation amount Each grounding transformer arc suppression coil is compensated according to the main unit's compensation amount. Slave compensation amount Adjust the gear and implement pre-adjustment compensation.

[0030] Step (3) specifically refers to: when a ground fault occurs in one phase of the system, such as Figure 3 As shown, if a phase A ground fault occurs, the transition resistance of the 10kV phase A ground fault in the system is R. d The provisional estimate of the ground capacitance reactance of the 10kV system is: The provisional estimate of the single-phase-to-ground capacitance current is: The neutral point voltage to ground is The voltage relative to ground of the fault is The ground fault current is Ia;

[0031] Both the grounding transformer arc suppression coil master and the grounding transformer arc suppression coil slave are pre-adjusted arc suppression coils. The compensation coefficients of the grounding transformer arc suppression coil master and each grounding transformer arc suppression coil slave are assigned as follows: k=0.5, k1=0.2, k2=0.2, where k is the compensation coefficient of the grounding transformer arc suppression coil master, k1 is the compensation coefficient of the first grounding transformer arc suppression coil slave, and k2 is the compensation coefficient of the second grounding transformer arc suppression coil slave.

[0032] The compensation currents for the main unit of the grounding transformer arc suppression coil, the slave unit of the first grounding transformer arc suppression coil, and the slave unit of the second grounding transformer arc suppression coil are respectively , , ;

[0033] When a ground fault occurs in one phase of the system, such as Figure 4 As shown, if a phase A ground fault occurs in the system,

[0034] like ;but ;

[0035] In the formula, This is a provisional estimate of the low-voltage system's capacitance-to-ground reactance. , Angular velocity, This is a provisional estimate of the capacitance to ground of the low-voltage system. For the inductive reactance of the grounding transformer arc suppression coil main unit, The inductance of the first grounding transformer arc suppression coil is the slave inductance. The second grounding transformer arc suppression coil slave inductance; This is the compensation current for the flexible grounding device;

[0036] at this time ;

[0037] In the formula, The voltage of phase A of the system;

[0038] That is, the flexible grounding device is injected At that time, the voltage to ground relative to the fault drops to 0, and the arc is completely extinguished;

[0039] Considering To estimate the value, a voltage feedback pair is introduced. Implement closed-loop control;

[0040] set up , , These are, respectively, the master inductance of the grounding transformer arc suppression coil, the slave inductance of the first grounding transformer arc suppression coil, and the slave inductance of the second grounding transformer arc suppression coil in the complex frequency domain. This is a provisional estimate of the system's capacitance reactance to ground in the complex frequency domain. This refers to the actual injected neutral point current in the complex frequency domain. This represents the actual value of the system's capacitance-to-ground reactance in the complex frequency domain. This represents the neutral point current that theoretically needs to be injected in the complex frequency domain.

[0041] Using the system phase A voltage Ea(s) in the complex frequency domain as the reference input of the closed-loop control system, and using Ua(s)' obtained by multiplying the fault phase (i.e., phase A voltage to ground) Ua(s) in the complex frequency domain by the feedback function F(s) as the negative feedback of the closed-loop control system, and using the input value of the closed-loop control system Ea'(s) = Ea(s) - Ua(s)', as follows: Figure 5 As shown, it can be seen that:

[0042] ; ;

[0043] In the formula, , The difference between the two, multiplied by the transition resistance Rd, forms the fault-to-ground voltage Ua(S) in the complex frequency domain. Ideally, Ua(S) is 0, but in actual operation... Due to the difficulty in accurately predicting and the existence of a certain ground resistance, Ua(s) is not zero and constantly changing. The actual sampled Ua(s) is used as the feedback input. By setting the feedback function F(s), which adopts the PID feedback control function, Ua(s)' after correction by F(s) is used as negative feedback and compared with Ea(s) to obtain the difference as the system input, thus forming a closed-loop control system with voltage as the feedback variable. The closed-loop control with voltage as the feedback variable does not require real-time cross-station tracking of relevant electrical quantities at each new energy plant. It only needs to use the fault bus voltage on the main station side of the system as the feedback input, that is, it does not rely on real-time communication to carry out system compensation.

[0044] Another objective of this invention is to provide a multi-terminal arc suppression coil collaborative control system based on neutral point flexible grounding, comprising:

[0045] The grounding transformer arc suppression coil main unit is deployed in the system substation. It adopts a pre-adjusted arc suppression coil with a maximum compensation capacity of Qs. It is designed to cover the single-phase grounding capacitance current of the lines from the system substation to each load line and the new energy plant line. It is responsible for replenishing the arc suppression coil current from the neutral point of the grounding transformer in the system substation.

[0046] The grounding transformer arc suppression coil slave unit is deployed in various new energy power plants. It adopts a pre-adjusted arc suppression coil with a maximum compensation capacity of Q. fi Considering the single-phase grounding capacitor current that can cover the collection lines of each new energy plant, it is responsible for replenishing the arc suppression coil current from the neutral point of the grounding transformer of each plant.

[0047] The flexible grounding device is deployed in the system substation. It adopts a PWM active inverter device and is connected in parallel with the grounding transformer arc suppression coil. It injects current into the neutral point of the grounding transformer according to the closed-loop control requirements and supports capacitive or inductive compensation switching.

[0048] The control host is deployed in the system substation and is responsible for monitoring the phase and zero-sequence voltage of each phase on the low-voltage side of the system substation, coordinating and distributing the compensation current of the grounding transformer arc suppression coil host and the grounding transformer arc suppression coil slave, and calculating the compensation current of the flexible grounding device.

[0049] The control slave unit is deployed in each new energy plant to receive commands from the control host and adjust the output current value of the arc suppression coil of each plant.

[0050] The fiber optic communication network connects the control host and control slave devices, transmitting control commands and status data.

[0051] As can be seen from the above technical solution, the beneficial effects of the present invention are as follows: First, the present invention adopts a hierarchical collaborative control architecture: adopting a master-slave mode, the control host of the arc suppression coil of the system substation acts as the master controller, and the control slave of the arc suppression coil of the new energy plant station acts as the slave device. Through an optical fiber communication network, collaborative compensation of the grid and plant arc suppression coils is achieved, solving the pain point of multi-point compensation and lack of coordination under single-phase grounding faults in the current grid system with distributed access to the arc suppression coil grounding of new energy plants; Second, based on the neutral point flexible grounding control mechanism: the system substation is equipped with a flexible grounding device, injecting neutral point current into the grounding transformer arc suppression coil host to provide arc suppression... The arc coil provides precise compensation, fully compensating for power frequency and active components to achieve 100% arc suppression. Third, voltage-based closed-loop dynamic control: the control host calculates the total compensation requirement in real time, without needing to dynamically track the relevant electrical quantities at each new energy plant. It only needs to use the fault bus voltage on the main station side of the system as feedback input, that is, it does not rely on real-time communication to carry out system compensation. It is particularly suitable for the characteristics of multi-point simultaneous compensation and difficulty in real-time coordination and synchronization under single-phase grounding faults in power grid systems with distributed access to arc suppression coil grounding of new energy plants. It dynamically adjusts the current injected into the neutral point by the flexible grounding device, and automatically switches between inductive and capacitive modes to avoid over / under-compensation. Attached Figure Description

[0052] Figure 1 This is a system structure diagram of the present invention;

[0053] Figure 2 This is a flowchart of the control method of the present invention;

[0054] Figure 3 This is a schematic diagram of the current when a phase A ground fault occurs in the system according to the present invention;

[0055] Figure 4 This is the equivalent circuit diagram when a phase A ground fault occurs in the system of this invention;

[0056] Figure 5 This is a block diagram of a closed-loop control system with voltage as the feedback variable in the complex frequency domain. Detailed Implementation

[0057] like Figure 1 , Figure 2 As shown, a multi-terminal arc suppression coil coordinated control method based on neutral point flexible grounding is proposed. The method includes the following sequential steps:

[0058] (1) Coordinated compensation allocation: The control host allocates the compensation coefficients of the grounding transformer arc suppression coil master and each grounding transformer arc suppression coil slave; the control host sends the arc suppression coil compensation amount to the control slave through the optical fiber communication network; the control host sends the compensation amount to the grounding transformer arc suppression coil master, and the control slave sends the compensation amount to each grounding transformer arc suppression coil slave; each grounding transformer arc suppression coil adjusts its gear according to the compensation amount and carries out pre-adjustment compensation;

[0059] (2) Fault detection and phase selection: The control host monitors the zero-sequence voltage of the system in real time. When the zero-sequence voltage exceeds 20% of the phase voltage, it is determined that a ground fault has occurred. Then, the amplitude of the three-phase voltage is compared to determine that the lowest phase is the faulty phase.

[0060] (3) Voltage-based closed-loop control: At the initial moment of a fault, the host controller controls the flexible grounding device to inject neutral point current. The closed-loop control mode is adopted, and the voltage of the fault relative to ground is used as the feedback input. The injected neutral point current is adjusted to make the voltage of the fault relative to ground 0. The injection time of the neutral point current is set to 10s.

[0061] (4) Fault identification: After the neutral point current is injected for 10 seconds, the injected neutral point current value is reduced. If the zero-sequence voltage of the system drops, it is determined to be a single-phase instantaneous ground fault; if the zero-sequence voltage of the system still exceeds 20% of the phase voltage after the neutral point current is stopped, it is determined to be a permanent fault.

[0062] Step (1) specifically refers to: the control host calculating the provisional value of the low-voltage system's capacitance to ground on a 24-hour cycle. Provisional estimate of single-phase ground capacitance current and corresponding system compensation amount ;

[0063] Provisional estimate of single-phase ground capacitance current for:

[0064] ;

[0065] In the formula, It is the rated voltage of the low-voltage system. It is angular velocity;

[0066] Corresponding system compensation amount for:

[0067] ;

[0068] The control host allocates the compensation coefficient of the grounding transformer arc suppression coil host. Compensation coefficients of each grounding transformer arc suppression coil slave unit 'i' represents the i-th grounding transformer arc suppression coil slave unit; the compensation current of the grounding transformer arc suppression coil master unit of the system station. for:

[0069] ;

[0070] According to the compensation coefficient Setting host inductive impedance and host compensation amount Among them, host inductive impedance for:

[0071] ;

[0072] Host compensation amount for:

[0073] ;

[0074] Compensation current of the slave unit of the grounding transformer arc suppression coil in each new energy power plant for:

[0075] ;

[0076] According to the compensation coefficient Setting the slave sensor resistance and corresponding slave compensation amount Among them, from machine-sensory resistance for:

[0077] ;

[0078] Slave compensation amount for:

[0079] ;

[0080] The control host sends slave compensation values ​​to the control slave via a fiber optic communication network every 24 hours. The control host and control slave respectively send the host compensation amount to the grounding transformer arc suppression coil host and the grounding transformer arc suppression coil slave. Slave compensation amount Each grounding transformer arc suppression coil is compensated according to the main unit's compensation amount. Slave compensation amount Adjust the gear and implement pre-adjustment compensation.

[0081] It should be guaranteed that 0.8 ≤ k + k1 + k2 … k n ≤1.2, 1≤i≤n;

[0082] If there are no effective fiber optic communication resources between the system substation and each new energy plant, the compensation amount of the arc suppression coil slave unit of the grounding transformer at each new energy plant... It can be manually configured to report monthly to the system substation control host, and should meet 0.8Q. c ≤Q' s +Q' f1 +Q' f2 …Q' fn ≤1.2Q c The control host compensates according to the compensation amount of each slave unit. The compensation current of the slave device is calculated. and from machine-sensory resistance We will carry out voltage-based closed-loop control.

[0083] Step (3) specifically refers to: when a ground fault occurs in one phase of the system, if a ground fault occurs in phase A, the transition resistance of the 10kV phase A ground fault in the system is R. d The provisional estimate of the ground capacitance reactance of the 10kV system is: The provisional estimate of the single-phase-to-ground capacitance current is: The neutral point voltage to ground is The voltage relative to ground of the fault is The ground fault current is Ia;

[0084] Both the grounding transformer arc suppression coil master and the grounding transformer arc suppression coil slave are pre-adjusted arc suppression coils. The compensation coefficients of the grounding transformer arc suppression coil master and each grounding transformer arc suppression coil slave are assigned as follows: k=0.5, k1=0.2, k2=0.2, where k is the compensation coefficient of the grounding transformer arc suppression coil master, k1 is the compensation coefficient of the first grounding transformer arc suppression coil slave, and k2 is the compensation coefficient of the second grounding transformer arc suppression coil slave.

[0085] The compensation currents for the main unit of the grounding transformer arc suppression coil, the slave unit of the first grounding transformer arc suppression coil, and the slave unit of the second grounding transformer arc suppression coil are respectively , , ;

[0086] When a ground fault occurs in one phase of the system, if a ground fault occurs in phase A of the system,

[0087] like ;but ;

[0088] In the formula, This is a provisional estimate of the low-voltage system's capacitance-to-ground reactance. , Angular velocity, This is a provisional estimate of the capacitance to ground of the low-voltage system. For the inductive reactance of the grounding transformer arc suppression coil main unit, The inductance of the first grounding transformer arc suppression coil is the slave inductance. The second grounding transformer arc suppression coil slave inductance; This is the compensation current for the flexible grounding device;

[0089] at this time ;

[0090] In the formula, The voltage of phase A of the system;

[0091] That is, the flexible grounding device is injected At that time, the voltage to ground relative to the fault drops to 0, and the arc is completely extinguished;

[0092] Considering To estimate the value, a voltage feedback pair is introduced. Implement closed-loop control;

[0093] set up , , These are, respectively, the master inductance of the grounding transformer arc suppression coil, the slave inductance of the first grounding transformer arc suppression coil, and the slave inductance of the second grounding transformer arc suppression coil in the complex frequency domain. This is a provisional estimate of the system's capacitance reactance to ground in the complex frequency domain. This refers to the actual injected neutral point current in the complex frequency domain. This represents the actual value of the system's capacitance-to-ground reactance in the complex frequency domain. This represents the neutral point current that theoretically needs to be injected in the complex frequency domain.

[0094] Using the system phase A voltage Ea(s) in the complex frequency domain as the reference input of the closed-loop control system, and using Ua(s)' obtained by multiplying the fault phase (i.e., phase A) voltage to ground in the complex frequency domain by the feedback function F(s) as the negative feedback of the closed-loop control system, and using the input value of the closed-loop control system Ea'(s) = Ea(s) - Ua(s)', it can be seen that:

[0095] ; ;

[0096] In the formula, , The difference between the two, multiplied by the transition resistance Rd, forms the fault-to-ground voltage Ua(S) in the complex frequency domain. Ideally, Ua(S) is 0, but in actual operation... Due to the difficulty in accurately predicting and the existence of a certain ground resistance, Ua(s) is not zero and constantly changing. The actual sampled Ua(s) is used as the feedback input. By setting the feedback function F(s), which adopts the PID feedback control function, Ua(s)' after correction by F(s) is used as negative feedback and compared with Ea(s) to obtain the difference as the system input, thus forming a closed-loop control system with voltage as the feedback variable. The closed-loop control with voltage as the feedback variable does not require real-time cross-station tracking of relevant electrical quantities at each new energy plant. It only needs to use the fault bus voltage on the main station side of the system as the feedback input, that is, it does not rely on real-time communication to carry out system compensation.

[0097] This system includes:

[0098] The grounding transformer arc suppression coil main unit is deployed in the system substation. It adopts a pre-adjusted arc suppression coil with a maximum compensation capacity of Qs. It is designed to cover the single-phase grounding capacitance current of the lines from the system substation to each load line and the new energy plant line. It is responsible for replenishing the arc suppression coil current from the neutral point of the grounding transformer in the system substation.

[0099] The grounding transformer arc suppression coil slave unit is deployed in various new energy power plants. It adopts a pre-adjusted arc suppression coil with a maximum compensation capacity of Q. fi Considering the single-phase grounding capacitor current that can cover the collection lines of each new energy plant, it is responsible for replenishing the arc suppression coil current from the neutral point of the grounding transformer of each plant.

[0100] The flexible grounding device is deployed in the system substation. It adopts a PWM active inverter device and is connected in parallel with the grounding transformer arc suppression coil. It injects current into the neutral point of the grounding transformer according to the closed-loop control requirements and supports capacitive or inductive compensation switching.

[0101] The control host is deployed in the system substation and is responsible for monitoring the phase and zero-sequence voltage of each phase on the low-voltage side of the system substation, coordinating and distributing the compensation current of the grounding transformer arc suppression coil host and the grounding transformer arc suppression coil slave, and calculating the compensation current of the flexible grounding device.

[0102] The control slave unit is deployed in each new energy plant to receive commands from the control host and adjust the output current value of the arc suppression coil of each plant.

[0103] The fiber optic communication network connects the control host and control slave devices, transmitting control commands and status data.

[0104] In summary, this invention adopts a hierarchical collaborative control architecture: It employs a master-slave mode, with the control host of the arc suppression coil in the system substation acting as the master controller, and the control slave of the arc suppression coil in the new energy plant acting as the slave device. Collaborative compensation of the grid and plant arc suppression coils is achieved through an optical fiber communication network. A neutral-point flexible grounding-based control mechanism is used: the system substation is equipped with a flexible grounding device, injecting neutral-point current into the grounding transformer's arc suppression coil host to precisely supplement the arc suppression coil, fully compensating for both power frequency and active components, achieving 100% arc suppression. Voltage-based closed-loop dynamic control: the control host calculates the total compensation requirement in real time, without needing to track relevant electrical quantities at each new energy plant in real time. It only needs to use the fault bus voltage on the system master station side as feedback input, i.e., it does not rely on real-time communication to carry out system compensation, dynamically adjusting the current injected into the neutral point by the flexible grounding device, and automatically switching between inductive and capacitive modes to avoid over / under-compensation.

[0105] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A neutral point flexible grounding based multi-terminal arc suppression coil cooperative control method, characterized in that: The method comprises the following steps in sequence: (1) Cooperative compensation distribution: the control host distributes compensation coefficients of the grounding transformer arc suppression coil host and each grounding transformer arc suppression coil slave; the control host sends the arc suppression coil compensation amount to the control slave through the optical fiber communication network; the control host sends the compensation amount to the grounding transformer arc suppression coil host, and the control slave sends the compensation amount to each grounding transformer arc suppression coil slave; each grounding transformer arc suppression coil adjusts the gear according to the compensation amount and carries out pre-adjustment compensation; (2) Fault detection and phase selection: the control host monitors the zero sequence voltage of the system in real time; when the zero sequence voltage exceeds 20% of the phase voltage, it is determined that a grounding fault occurs; then the amplitudes of the three-phase voltages are compared to determine the lowest phase as the fault phase; (3) Voltage-based closed-loop control: at the initial moment of the fault, the control host controls the flexible grounding device to inject a neutral point current; a closed-loop control mode is adopted, the fault phase-to-ground voltage is used as the feedback input, the injected neutral point current is adjusted to make the fault phase-to-ground voltage 0, and the injection time of the neutral point current is set to 10s; (4) Fault discrimination: after the neutral point current is injected for 10s, the injected neutral point current value is reduced; if the system zero sequence voltage decreases, it is determined to be a single-phase transient ground fault; if the system zero sequence voltage still exceeds 20% of the phase voltage after the neutral point current is stopped, it is determined to be a permanent fault.

2. The neutral point flexible grounded multi-terminal arc suppression coil coordinated control method according to claim 1, characterized in that: Step (1) is specifically referring to: control the host computer to 24 hours for the period, the low-voltage system of earth capacitance temporary estimate value , single-phase earth capacitance current temporary estimate value And the corresponding system compensation ; Single phase to ground capacitance current transient estimate Is = 0. ； wherein is the rated voltage of the low voltage system, is the angular velocity; The corresponding system compensation amount is: ； Control host distributes the compensation coefficient of the grounding transformer arc suppression coil host , the compensation coefficient of each grounding transformer arc suppression coil slave ; the compensation current of the grounding transformer arc suppression coil host of the system station is: ； According to the compensation coefficient Setting the host inductance And the host compensation amount Wherein, the host inductance Is: ； Host compensation amount is: ； The compensation current of the grounding transformer arc suppression coil slave of each new energy plant station Is: ； According to the compensation coefficient The slave inductance And the corresponding slave compensation amount Wherein, the slave inductance Is: ； From the machine compensation amount is: ； The control host sends slave compensation values ​​to the control slave via a fiber optic communication network every 24 hours. The control host and control slave respectively send the host compensation amount to the grounding transformer arc suppression coil host and the grounding transformer arc suppression coil slave. Slave compensation amount Each grounding transformer arc suppression coil is compensated according to the main unit's compensation amount. Slave compensation amount Adjust the gear and implement pre-adjustment compensation.

3. The neutral point flexible grounded multi-terminal arc suppression coil coordinated control method according to claim 1, characterized in that: Step (3) is specifically as follows: when a phase of the system occurs a ground short circuit, if the A phase occurs a ground short circuit, the transition resistance of the 10 kVA phase of the system 10 kV occurs a ground short circuit is R d , the temporary estimated value of the ground capacitance reactance of the 10 kV system is , the temporary estimated value of the single-phase ground capacitance current is , the neutral point voltage is , the fault phase voltage is , and the ground short circuit current at the fault point is Ia. The grounding transformer arc suppression coil host and the grounding transformer arc suppression coil slave are both pre-adjustment arc suppression coils; the compensation coefficients of the grounding transformer arc suppression coil host and each grounding transformer arc suppression coil slave are distributed, k=0.5, k1=0.2, and k2=0.2, wherein k is the compensation coefficient of the grounding transformer arc suppression coil host, k1 is the compensation coefficient of the first grounding transformer arc suppression coil slave, and k2 is the compensation coefficient of the second grounding transformer arc suppression coil slave; The compensation currents of the ground transformer arc suppression coil master, the first ground transformer arc suppression coil slave and the second ground transformer arc suppression coil slave are respectively , , ; When a single-phase grounding short circuit occurs in the system, if the A-phase grounding short circuit occurs in the system, If ; then ; wherein is a temporary estimate of the low voltage system earth capacitance reactance, , is the angular velocity, is a temporary estimate of the low voltage system earth capacitance; is the main machine inductance of the grounding transformer arc suppression coil, is the slave machine inductance of the first grounding transformer arc suppression coil, is the slave machine inductance of the second grounding transformer arc suppression coil; is the compensation current of the flexible grounding device; At this time ; In the formula, is the system A phase voltage; That is, the flexible grounding device injects When the fault phase voltage drops to 0, the arc is completely extinguished. Taking into account For the estimated value, introduce voltage feedback to Carry out closed-loop control; Let , , be the master ground transformer arc suppression coil inductance, the first ground transformer arc suppression coil slave inductance, and the second ground transformer arc suppression coil slave inductance in the complex frequency domain, respectively, be the temporary estimate of the system ground capacitance reactance in the complex frequency domain, be the actual injected neutral point current in the complex frequency domain, be the actual value of the system ground capacitance reactance in the complex frequency domain, be the theoretically required injected neutral point current in the complex frequency domain; The system A-phase voltage Ea(s) in the complex frequency domain is used as the reference input of the closed-loop control system, and the A-phase-to-ground voltage Ua(s) in the complex frequency domain multiplied by the feedback function F(s) is used as the negative feedback of the closed-loop control system, so that Ea'(s)=Ea(s)-Ua(s)' is the input value of the closed-loop control system, and it can be known that: ； ； In the formula, , The difference between the two multiplied by the transition resistance Rd forms the fault phase-to-ground voltage Ua(S) in the complex frequency domain. In the ideal state, Ua(s) is 0, and in the actual operation It is difficult to accurately estimate and there is a certain ground resistance, Ua(s) is not 0 and constantly changing. With the actual sampled Ua(s) as the feedback input, by setting the feedback function F(s), F(s) adopts the PID feedback control function, after correction by F(s) Ua(s)' as negative feedback and Ea(s) comparison difference as system input, constitute a closed-loop control system with voltage as feedback variable; With voltage as feedback variable, the closed-loop control does not need to track the related electrical quantities of each new energy plant station in real time, only needs to take the fault bus voltage of the system master station side as the feedback input, that is, does not depend on real-time communication to carry out system compensation.

4. A system implementing the neutral point flexible grounded multi-terminal arc suppression coil coordinated control method according to any one of claims 1 to 3, characterized in that: It comprises: The grounding transformer arc suppression coil host is deployed in the system substation, adopts a pre-adjustment arc suppression coil, has a maximum compensation capacity Qs, can cover single-phase grounding capacitive current of the system substation to each load line and the new energy plant line, and is responsible for injecting the arc suppression coil current from the system substation grounding transformer neutral point; Grounding transformer arc suppression coil slave, deployed in each new energy plant station, using pre-adjusting arc suppression coil, the maximum compensation capacity is Q fi , considering that the single-phase grounding capacitance current of the collection line of each new energy plant station can be covered, the arc suppression coil current is compensated from the neutral point of each plant grounding transformer; The flexible grounding device is deployed in the system substation, adopts a PWM active inverter device, is connected in parallel with the grounding transformer arc suppression coil host, injects the current into the grounding transformer neutral point according to the closed-loop control requirement, and supports capacitive or inductive compensation switching; The control host is deployed in the system substation, is responsible for monitoring the voltages of each phase and zero sequence on the low-voltage side of the system substation, coordinating the compensation currents of the grounding transformer arc suppression coil host and the grounding transformer arc suppression coil slave, and calculating the compensation current of the flexible grounding device; The control slave is deployed in each new energy plant, receives the instruction of the control host, and adjusts the output arc suppression coil current value of each plant. Optical fiber communication network, connecting control master, control slave, transmitting control command and state data.

Images