Short-circuit fault limiter based on rectifier capacitor current nature commutation

Abstract

The invention provides a short-circuit fault limiter based on rectifier capacitor current nature commutation. The device is characterized by establishing a current limiter topological structure through theoretical analysis and pre-estimating feasibility, carrying out formula derivation to analyze in detail a current limiting process, and finally, carrying out simulation experiment to verify current limiting performance. The current limiting process of a current limiter can experience three stages: a short-circuit current normal rising stage before switch action, a brief commutation and voltage stabilization stage of a full-bridge rectifier capacitor charging circuit, and a current-limiting inductor complete involvement current-limiting stage. Normal operation of a power grid is not influenced when the current limiter does not act; after the current limiter acts, a short-circuit current value can be reduced greatly, and bus voltage drop is reduced obviously; a current-limiting inductor (L) and a charging capacitor (C) have an optimal coordination relationship, and thus an optimal current limiting effect can be achieved; and the device is low in harmonic content and has no hazard overvoltage.

Description

technical field [0001] The invention belongs to the technical field of short-circuit current limiting protection for power supply systems, and more specifically relates to a short-circuit fault limiter based on the natural commutation of rectifying capacitor current. Background technique [0002] With the increasing scale of the power grid, the short-circuit current continues to rise, even exceeding the breaking capacity of the existing circuit breaker, which is more and more harmful to various electrical equipment. Traditional current limiting measures, such as the use of DC networking technology, The neutral point of the transformer is grounded through a small reactance and the interrupting capacity of the circuit breaker is increased, which can limit the short-circuit current to varying degrees, but at the same time it will also bring about one or the other negative effects, so the fault current limiter (fault current limiter , FCL) research is imperative; FCL can be roug...

AI Technical Summary

Problems solved by technology

[0002] With the increasing scale of the power grid, the short-circuit current continues to rise, even exceeding the breaking capacity of the existing circuit breaker, which is more and more harmful to various electrical equipment. Traditional current limiting measures, such as the use of DC networking technology, The neutral point of the transformer is grounded through a small reactance and the interrupting capacity of the circuit breaker is increased, which can limit the short-circuit current to varying degrees, but at the same time it will also bring about one or the other negative effects, so the fault current limiter (fault current limiter , FCL) research is imperative; FCL can be roughly divided into two types: material type and non-material type: material type FCL achieves the purpose of current limitation according to the characteristic that its resistance value will change with temperature, such as superconductor FCL and PTC resistor FCL, etc., but the heat dissipation and cooling costs are too expensive, so the material type FCL can only be used in the medium and low voltage power grid at present; the non-material type FCL uses the method of changing its own topology to adjust its equivalent impedance to limit the current , such as magnetic saturation FCL, solid-state FCL, resonant FCL, etc.; from the perspective of technology and economy, non-material FCL is more suitable for high-voltage power grids

[0003] The series reactor type FCL originally proposed is to connect the reactor in parallel with the fast switch. When the line is working normally, the fast switch is closed, the reactor is short-circuited, and the FCL has no effect on the line. When a short-circuit fault occurs, the fast switch is disconnected, and the reactor It is connected to the line to limit the current, but because the current cannot change suddenly when the reactor is first connected, it is equivalent to an open circuit, so a high overvoltage will be generated at both ends of the switch, which may cause an arc at the switch, and the switch cannot Normal breaking, FCL can not play a good role in current limiting

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