The Research On The Algorithm Optimization Of DC Protection System In Gao-Zhao HVDC Project

DC transmission over load usually refers to the DC current higher than the rating, theoverload ability refers to DC current higher than the rating size and continuous time length. Inthe over load cases, may need to be considered acceptable equipment life expectancydecreased and the standby cooling equipment and below established the use of environmentaltemperature. One pole locking then another pole in the over load operation period locked bythe overcurrent protection action happenned many times in Gao-Zhao HVDC project, it needsto solve the problems of the over-current protection action by may be harmonic, pulseinterference factors, to avoid DC system in over load operation appear again appears thesimilar problem, then it can improve Gao-Zhao HVDC project’s safe operation reliability.First of all, The thesis analyzes Gao-Zhao HVDC project DC protection system in detailfrom protection area, protection design principle, overall structure, redundancy configuration,protection function etc., and researches the project over load capacity and all previous faultreasons systematically.Secondly, it analyzes the overcurrent protection algorithm, and through the analysis ofthe failure cause gets optimization solution, makes preliminary validation using PSCADsimulation software.Finally, it makes he optimized algorithm system test verification using the Gao-ZhaoHVDC project RTDS simulation platform. The test results proved that modified algorithmcan avoid the over-current protection malfunction during the period of over load operation.When the system the real fault, such as in valve side interphase short circuit, valve arm shortcircuit, valve side single-phase grounding, inverter bridge midpoint of short circuit, valvegroup of short circuit,12pulse valve group of short circuit and high voltage DC bus valveside grounding fault, etc, and the over load limiter fault, the DC overcurrent protection faultresponse behavior are all correct, it can satisfy the system requirements, protects overcurrentprotection from the malfunction and refuse to act.This thesis puts forward the DC overcurrent protection optimization scheme is feasible,which can effectively solve the problem that Gao-Zhao HVDC project over-current protectionmalfunction in the over load operation period.