Distribution network ground fault arc suppression method based on three-phase cascade H bridge converters

Abstract

The invention relates to a distribution network ground fault arc suppression method based on three-phase cascade H bridge converters. The three-phase cascade H bridge converters are adopted to replace arc suppression coils and mounted between phase lines and the ground, and power is supplied to capacitors on the direct current side of the converters by using phase voltages, so that boosting transformers and grounding transformers are saved, and the problem of source taking difficulty on the direct current side of the converters is solved. The converters inject current to a distribution network in a phase splitting mode to compensate the total current of a ground fault to be zero or to inhibit the phase voltage of the fault to be zero, so that the arc is automatically extinguished; and the reference compensation current is calculated by using real-time measured zero sequence voltage, so that the fault phase identification link is saved. The operation is simplified by using the voltage arc suppression method of controlling the zero sequence voltage to adjust the injected compensation current. In view of the influence of circuit parameters and load current on the arc suppression effect and the deduced relation between the ground fault residual current after the voltage arc suppression method is applied and the zero sequence voltage after the fault, an adaptive arc suppression method is put forward by using the zero sequence voltage as a voltage and current arc suppression method.

Description

technical field [0001] The invention relates to a grounding fault arc suppression method for a distribution network based on a three-phase cascaded H-bridge converter. Background technique [0002] During the operation of the distribution network, there are a large number of instantaneous single-phase ground faults caused by complex reasons such as lightning strikes, tree branches and other foreign objects touching the wires for a short time, insulator fouling and breakdown, and cable insulation degradation. The non-effective grounding method, especially the resonant grounding method has the advantages of limiting the single-phase grounding fault current, automatically eliminating the instantaneous single-phase grounding fault, helping to extinguish the arc formed by the grounding capacitor current at the fault point, and improving the reliability of power supply. Widely used in voltage distribution network. However, with the increasing scale of the distribution network and...

AI Technical Summary

Problems solved by technology

[0007] The existing passive current arc suppression technology has the following defects: the passive current arc suppression technology can only compensate the reactive component of the ground fault current, but cannot compensate the harmonic component and active component of the ground fault current, and the arc suppression effect is limited

[0008] The existing active current arc suppression technology has the following defects: the existing active current arc suppression method uses the power supply voltage to calculate the compensation current, and after the ground fault occurs, the fault phase needs to be identified first, and a single inverter is used as a supplementary arc suppression device When the output capacity is limited and the harmonic characteristics are poor, the step-up transformer and the grounding transformer need to be connected to the distribution network and need to be added to charge the DC side. In addition, the cooperation with the main arc suppression device needs to be considered

[0009] The existing passive voltage arc suppression technology has the following defects: the direct grounding method is affected by factors such as high-impedance grounding and resonant overvoltage due to the fault phase selection accuracy, and the wrong phase selection result will cause phase-to-phase faults; the impedance grounding method, When low-resistance grounding such as metal occurs, the shunt impedance of the shunt is small, which affects the effect of arc suppression

During the operation of the grounding circuit breaker, the fault arc cannot be effectively suppressed

In addition, when the arc suppression device is out of operation, the charge stored in the ground capacitance can only be released through the three-phase voltage transformer, which may cause the transformer to saturate, thereby causing ferromagnetic resonance

In practical applications, there are still problems such as difficulty in parameter configuration of grounding equipment

[0010] The existing active voltage arc suppression technology has the following defects: the calculation of the compensation current is relatively complicated in the open-loop control, and the repeated adjustment of the compensation current in the closed-loop control makes the response time of the arc suppression device longer, which cannot meet the requirements of ground fault arc suppression. requirements

[0011] The existing flexible adaptive arc suppression method has the following defects: it only considers the influence of line parameters on the arc suppression effect, and does not analyze the influence of fault feeder load current, and the transition resistance is used as the switching condition of the two arc suppression methods. The resistance cannot be measured directly and the calculation is more complicated

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