A voltage arc-extinguishing control method for single-phase ground fault of power distribution network

Abstract

A voltage arc suppression control method for single-phase ground faults in distribution networks belongs to the field of active arc suppression technology for single-phase ground faults in distribution networks. Its features include the following steps: Step a, acquiring signals; Step b, determining whether a ground fault has occurred; Step c, applying compensation based on a step coefficient k; Step d, determining whether the arc has been extinguished; Step e, determining whether the step coefficient k equals 1; Step f, applying compensation based on a secondary coefficient p; Step g, determining whether the arc has been extinguished; Step h, determining whether the secondary step coefficient p equals 0.1; Step i, the active inverter is continuously engaged according to the current output voltage. In this voltage arc suppression control method for single-phase ground faults in distribution networks, the impedance angle of the faulted line is used to determine the phase angle of the voltage drop from the fault point to the busbar, solving the problem that existing voltage arc suppression methods cannot reliably extinguish the arc and cause the fault current to increase instead of decrease when the fault point is far from the busbar and the fault transition resistance is small.

Description

Technical Field

[0001] A voltage arc suppression control method for single-phase grounding faults in distribution networks belongs to the field of active arc suppression technology for single-phase grounding faults in distribution networks. Background Technology

[0002] When a single-phase ground fault occurs in a distribution network, reducing the current at the fault point can extinguish the arc, thus mitigating the damage and preventing the accident from escalating. Arc suppression coils are common arc suppression devices in distribution networks, but they can only compensate for the reactive component of the ground fault current, not the active or harmonic components, and therefore cannot guarantee reliable arc extinguishing at the grounding point. Active arc suppression technology, which utilizes an active inverter as the active power source, can achieve full compensation for the ground fault current, ensuring reliable arc extinguishing at the grounding point.

[0003] There are two types of active arc suppression technology: voltage-based arc suppression and current-based arc suppression. In existing technologies:

[0004] Chinese invention patent application number 202111528989.X, filed on December 14, 2021, entitled "Active Voltage Arc Suppression Method Based on Neutral Point Injection Current," discloses a technical solution. This solution essentially reduces the current at the fault point by injecting current, belonging to the current-based arc suppression method. The drawback of the current-based arc suppression method is that it requires accurate measurement of the system structure, and measurement errors can easily affect the compensation effect.

[0005] Chinese invention patent application number 202010845611.1, filed on November 27, 2020, entitled "An Active Arc Extinguishing Method for Single-Phase Ground Faults in Distribution Networks," discloses a technical solution belonging to the voltage arc extinguishing method. Its principle is to extinguish the arc at the fault point by controlling the bus voltage of the faulty phase below the arc extinguishing voltage. Compared to the current arc extinguishing method, it does not require accurate measurement of the system structure. However, the current voltage arc extinguishing method ignores the line voltage drop from the fault point to the bus. When the fault point is far from the bus and the fault transition resistance is small, even if the bus voltage is controlled to zero, the fault point still has a high voltage, which cannot ensure reliable arc extinguishing, and may even lead to an abnormal situation where the fault point current increases instead of decreasing. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a voltage arc suppression control method for single-phase ground faults in distribution networks that uses the impedance angle of the faulted line to determine the phase angle of the line voltage drop from the fault point to the busbar. This method solves the problem that existing voltage arc suppression methods cannot reliably extinguish the arc when the fault point is far from the busbar and the fault transition resistance is small, and the fault point current increases instead of decreasing.

[0007] The technical solution adopted by this invention to solve its technical problem is: a voltage arc suppression control method for single-phase ground faults in a power distribution network, including an arc suppression control system, which includes a controller and an active inverter, characterized by the following steps:

[0008] Step a: The controller collects voltage and current signals from the power distribution network and the active inverter;

[0009] Step b: The controller determines whether a ground fault has occurred in the distribution network. If a ground fault has occurred, it identifies the faulty phase and executes step c. If no ground fault has occurred, it returns to step a.

[0010] Step c: The active inverter determines the voltage value for compensation based on the initial step factor k and then performs compensation.

[0011] Step d: The controller determines whether the arc at the fault point has been extinguished. If the arc is extinguished, proceed to step i; if the arc is not extinguished, proceed to step e.

[0012] Step e: The controller determines whether the initial step coefficient k is equal to 1. If the initial step coefficient k is equal to 1, proceed to step f. If the initial step coefficient k is not equal to 1, increase the initial step coefficient k and return to step c.

[0013] Step f: The active inverter determines the voltage value for compensation based on the second step coefficient p, and then performs compensation.

[0014] Step g: The controller determines whether the arc at the fault point has been extinguished. If the arc is extinguished, proceed to step i; if the arc is not extinguished, proceed to step h.

[0015] In step h, the controller determines whether the second step coefficient p is equal to 0.1. If the second step coefficient p is equal to 0.1, step i is executed. If the second step coefficient p is not equal to 0.1, the second step coefficient p is increased, and the process returns to step f.

[0016] Step i: The active inverter continues to operate according to the current output voltage.

[0017] Preferably, the voltage value used for compensation in step c is: in, k is the power supply voltage of the faulty phase. n This is the initial step coefficient after the nth increase.

[0018] Preferably, when n=0, the initial value k0 of the initial step coefficient k is the ratio of the neutral point voltage to the phase power supply voltage when a fault occurs in the distribution network line but the active inverter is not put into compensation.

[0019] Preferably, the voltage value used for compensation in step f is: in, p is the power supply voltage of the faulty phase. j It is the second step coefficient after the j-th increase.

[0020] Preferably, in step e, the initial step coefficient k increases by a percentage greater than or equal to 5% each time it increases.

[0021] Preferably, in step h, the percentage increase of the secondary step coefficient p is greater than or equal to 3% each time it increases.

[0022] Compared with the prior art, the beneficial effects of this invention are:

[0023] In the voltage arc extinguishing control method for single-phase ground faults in this distribution network, the impedance angle of the fault line is used to determine the phase angle of the line voltage drop from the fault point to the bus. By controlling the neutral point voltage of the system to be equal to the reverse vector sum of the fault phase power supply voltage and the line voltage drop voltage from the fault point to the bus, the voltage at the fault point is controlled to be zero during ground faults. This solves the abnormal problem of existing voltage arc extinguishing methods failing to reliably extinguish the arc and causing the fault point current to increase instead of decrease when the fault point is far from the bus and the fault transition resistance is small. Attached Figure Description

[0024] Figure 1 This is a flowchart of a voltage arc suppression control method for single-phase grounding faults in a power distribution network.

[0025] Figure 2 This is a structural diagram of a voltage arc suppression control system for a single-phase ground fault in a power distribution network.

[0026] Figure 3 The simulation sampling waveform of the grounding point current is shown in the voltage arc suppression control method for single-phase grounding faults in power distribution networks. Detailed Implementation

[0027] Figures 1-3 This is the preferred embodiment of the present invention, which is described below in conjunction with the accompanying drawings. Figures 1-3 The present invention will be further described below.

[0028] like Figure 1 As shown, a voltage arc suppression control method for single-phase ground faults in a power distribution network (hereinafter referred to as the voltage arc suppression control method) includes the following steps:

[0029] Step 1001, Begin;

[0030] like Figure 2 As shown, this voltage arc suppression control method includes an arc suppression control system, wherein the phase voltages of the three phase lines A, B, and C of the system are respectively The power supply voltage of the three phase lines A, B, and C is Zero-sequence voltage (or neutral point voltage) is The neutral point zero-sequence impedance of the system is ZL The current during a ground fault is Z in resonant grounding system L The zero-sequence impedance of the arc suppression coil. For the compensation current of the arc suppression coil, Z is the current in an ungrounded system. L Approximately ∞ The output compensation current of the active inverter is 0; The three-phase ground capacitance of the system is C A C B C C The three-phase resistance to ground is R. A R B R C In practical applications, R is ignored. A R B R C The influence of grounding point transition resistance is R f The grounding point current is

[0031] The controller of the arc suppression control system measures signals such as phase voltage, zero-sequence voltage, active inverter injection current, and arc suppression coil compensation current (in a resonant grounding system) in real time through various instrument transformers. It detects grounding faults and controls the switching of the active inverter and the output compensation target. The active inverter outputs a single-phase AC power with controlled amplitude and phase angle, which is injected into the system neutral point via a step-up transformer.

[0032] Step 1002: Determine if a grounding fault has occurred;

[0033] The controller measures the three-phase voltage and zero-sequence voltage of the system in real time. The zero-sequence voltage amplitude was detected to exceed the set threshold. ( It is generally set to 15% of the phase power supply voltage. If a ground fault is detected, proceed to step 1003; otherwise, return to step 1001.

[0034] Step 1003: Identify the faulty phase;

[0035] The controller compares the phase voltage amplitudes of the three phase lines after the fault occurs and determines that the faulty phase is one of phases A, B, or C.

[0036] Step 1004: Determine the step factor and compensation voltage of the compensation voltage;

[0037] Determine the initial value k0 of the step coefficient k when the active inverter is put into compensation. k0 is the ratio of the neutral point voltage to the phase power supply voltage when a fault occurs in the distribution network line but the active inverter is not put into compensation.

[0038] And obtain the voltage value for compensation: in, Let n be the power supply voltage of the faulty phase. When initially connected, n = 0.

[0039] Step 1005: Active inverter compensation is activated;

[0040] The active inverter engages compensation according to the compensation voltage value determined in step 1004.

[0041] Step 1006: Has the arc been extinguished at the fault point?

[0042] The controller determines whether the arc at the fault point has been extinguished. If the arc is extinguished, proceed to step 1014; otherwise, proceed to step 1007.

[0043] Step 1007: Is the step coefficient k equal to 1?

[0044] The controller determines whether the step coefficient k is 1. If k ≠ 1, it executes step 1008; if k == 1, it executes step 1009.

[0045] Step 1008: Increase the step coefficient k;

[0046] Increase the step size k, and for each increase in step size k, increment the value of n by 1, i.e., n = n + 1. Furthermore, the increase in step size k should be greater than or equal to 5%, i.e., k n -k n-1 ≥5% (0.05). After increasing the step factor k, return to step 1005 to determine the new input compensation voltage value for the active inverter.

[0047] Step 1009 introduces new step coefficients and vectors;

[0048] Introducing a new step coefficient p (initial value p0) and a new phasor Power supply voltage of the faulty phase Rotation angle Obtain and determine the new input voltage of the active inverter: The initial value of j is 0, and the initial value of the step coefficient p is 0.

[0049] Step 1010: The active inverter is put into compensation.

[0050] The active inverter is compensated according to the newly determined output voltage in step 1008;

[0051] Step 1011: Has the arc been extinguished at the fault point?

[0052] The controller determines whether the arc at the fault point has been extinguished. If the arc is extinguished, proceed to step 1014; otherwise, proceed to step 1012.

[0053] Step 1012: Is the step coefficient p equal to 0.1?

[0054] The controller determines whether the step coefficient p is 0.1. If p ≠ 0.1, it executes step 1013. If p == 0.1, it executes step 1014.

[0055] Step 1013, increase the step coefficient p;

[0056] Increase the step size p, and for each increase in step size p, increment the value of j by 1, i.e., j = j + 1, and the increase in step size p should be greater than or equal to 3%, i.e.: p j -p j-1 ≥3% (0.03). After increasing the step factor p, return to step 1009 to determine the new input compensation voltage value for the active inverter.

[0057] Step 1014: The active inverter maintains its current output;

[0058] The active inverter continues to operate according to the current output voltage.

[0059] The voltage arc suppression control method described above is verified using the Matlab / Simulink simulation system. The simulation covers a 10kV system with a transition resistance of 10Ω and a single-phase ground fault 1km from the busbar. Figure 3 As shown, when this voltage arc suppression control method is used, the grounding current is almost zero after the active inverter is put into operation in 0.16s.

[0060] Using the Matlab / Simulink simulation system, a 10kV system with a fault point 1km away from the busbar was simulated for single-phase ground faults with different transition resistance values. The test results of the grounding point current using this method and the existing voltage arc suppression method are compared, as shown in Table 1:

[0061] Table 1 Comparison of grounding point current test results between this method and existing voltage arc suppression methods.

[0062]

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A voltage arc suppression control method for single-phase ground faults in a distribution network, comprising an arc suppression control system, the arc suppression control system including a controller and an active inverter, characterized in that: Includes the following steps: Step a: The controller collects voltage and current signals from the power distribution network and the active inverter; Step b: The controller determines whether a ground fault has occurred in the distribution network. If a ground fault has occurred, it identifies the faulty phase and executes step c. If no ground fault has occurred, it returns to step a. Step c: The active inverter determines the voltage value for compensation based on the initial step factor k and then performs compensation. Step d: The controller determines whether the arc at the fault point has been extinguished. If the arc is extinguished, proceed to step i; if the arc is not extinguished, proceed to step e. Step e: The controller determines whether the initial step coefficient k is equal to 1. If the initial step coefficient k is equal to 1, proceed to step f. If the initial step coefficient k is not equal to 1, increase the initial step coefficient k and return to step c. Step f: The active inverter determines the voltage value for compensation based on the second step coefficient p, and then performs compensation. Step g: The controller determines whether the arc at the fault point has been extinguished. If the arc is extinguished, proceed to step i; if the arc is not extinguished, proceed to step h. In step h, the controller determines whether the second step coefficient p is equal to 0.

1. If the second step coefficient p is equal to 0.1, step i is executed. If the second step coefficient p is not equal to 0.1, the second step coefficient p is increased, and the process returns to step f. Step i: The active inverter continues to operate according to the current output voltage.

2. The voltage arc suppression control method for single-phase grounding faults in distribution networks according to claim 1, characterized in that: The voltage value used for compensation in step c is, ,in, k is the power supply voltage of the faulty phase. n This is the initial step coefficient after the nth increase.

3. The voltage arc suppression control method for single-phase grounding faults in distribution networks according to claim 2, characterized in that: When n=0, the initial value k0 of the initial step coefficient k is the ratio of the neutral point voltage to the phase power supply voltage when a fault occurs in the distribution network line but the active inverter is not put into compensation.

4. The voltage arc suppression control method for single-phase grounding faults in distribution networks according to claim 1, characterized in that: The voltage value for compensation in step f is, ,in, p is the power supply voltage of the faulty phase. j The step coefficient is the second step coefficient after the j-th increase. For the faulty phase power supply voltage Rotation angle The resulting phasor.

5. The voltage arc suppression control method for single-phase grounding faults in distribution networks according to claim 1, characterized in that: In step e, the initial step coefficient k increases by a percentage greater than or equal to 5% each time.

6. The voltage arc suppression control method for single-phase grounding faults in distribution networks according to claim 1, characterized in that: In step h, each time the secondary step coefficient p increases, its percentage increase is greater than or equal to 3%.

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