Single-phase alternating-current line protection method and system for alternating-current and direct-current system

Abstract

The invention relates to a single-phase alternating-current line protection method and system for an alternating-current and direct-current system and belongs to the technical field of relay protection, thereby solving a problem of relatively low judgment accuracy possibly caused by maloperation or refusal of an existing protection method for protection of the alternating-current and direct-current system with rich harmonic and aperiodic components. The method comprises the following steps: acquiring three-phase voltage and three-phase current of an inverter side alternating current bus and three-phase current flowing from an inverter to the alternating current bus; based on a zero-mode equivalent circuit of the AC-DC interconnected power grid, obtaining a voltage and current equation of acertain fault of the inverter side related to an AC bus by adopting a KCL theorem and a KVL theorem; obtaining a fault distance based on the three-phase voltage and the three-phase current of the alternating current bus, the three-phase current flowing from the inverter to the alternating current bus and a voltage and current equation; and the fault type is judged and the inverter side circuit breaker is controlled to execute the corresponding action according to the generated circuit breaker control signal so that protection of the single-phase alternating current line can be realized and applicability and accuracy can be enhanced.

Description

technical field [0001] The invention relates to the technical field of relay protection, in particular to a single-phase AC line protection method and system for an AC-DC system. Background technique [0002] When the AC line on the inverter side fails, the inverter station is easily affected and commutation failure occurs. Coupled with the flexible and fast control of the DC system, the DC system presents strong nonlinear characteristics. In addition, when a commutation failure occurs, it is equivalent to a superimposed fault in the AC and DC system, and the DC system as an additional fault source brings a huge challenge to the reliability of the AC protection action. [0003] When the AC line fault causes commutation failure on the inverter side, the DC side can be equivalent to a controlled current source, and the inverter injects a large number of high-order harmonics and aperiodic components into the AC system, and the aperiodic components exhibit exponential decay char...

AI Technical Summary

Problems solved by technology

[0005] In view of the above analysis, the embodiment of the present invention aims to provide a single-phase AC line protection method and system for AC and DC systems, so as to solve the problem of misoperation of the existing protection methods for the protection of AC and DC systems with rich harmonic and aperiodic components. Or refusal to move may cause low judgment accuracy

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