DC Line Fault Protection Method Based on Converter Injection Characteristic Signal

Abstract

The invention discloses a DC line fault protection method based on a current converter injection characteristic signal. The method comprises the following steps: step 1: establishing a full-bridge modular multilevel current converter; step 2: when a DC line fault occurs, starting a characteristic signal injection strategy to inject the characteristic signal after a fault clearing strategy is started for a certain time, wherein the characteristic signal injection strategy can generate an identifiable characteristic signal in the line; and step 3, after the characteristic signal injection strategy is started, judging whether the fault exists through wavefront refraction. By adoption of the DC line fault protection method disclosed by the invention, permanent faults and transient faults can be quickly distinguished, when the fault is determined as the permanent fault, the fault distance can be accurately judged, and a function of fast restart of a fast arc-extinguishing fault and the non-start of the permanent fault is achieved; and by adoption of the DC line fault protection method disclosed by the invention, adaptive restart is achieved on a DC overhead line, adaptive identificationof the fault nature and the fast restart of the fast arc-extinguishing fault are achieved, the safe and reliable operation of a DC system is ensured, the power outage loss is reduced, and the directbenefit and the indirect benefit are very significant.

Description

technical field [0001] The invention belongs to the field of DC line fault protection, in particular to a DC line fault protection method based on a converter injection characteristic signal. Background technique [0002] Most of the faults in the power system come from overhead lines. Operation experience shows that line faults are single-phase (polar) and instantaneous. After the line fault is removed, the probability of successful reclosing within a fixed time limit is 60% to 90%. The higher the voltage level, the higher the reclosing power. Automatic reclosing is widely used in AC lines, which improves the reliability of power supply and has huge social and economic benefits. However, if it coincides with a permanent fault, the power system will suffer two consecutive fault impacts in a short period of time, which will reduce the insulation of electrical equipment and reduce its service life. [0003] At present, when the flexible HVDC restarts, it does not distinguish...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to provide a DC line fault protection method based on the characteristic signal injected by the converter, aiming to solve the problem of non-selective restart of the existing DC transmission

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