特高压混合直流LCC站低端换流器触发异常导致高端换流器过压闭锁原因分析

Analysis of Overvoltage Tripping of High-end Converters Caused by Abnormal Triggering of Low-end Converter in LCC Station of UHV Hybrid DC Project

基于昆柳龙多端混合直流工程昆龙两端运行工况下LCC站低端换流器触发异常、直流电压降低导致高端换流器过压跳闸的一起故障,分析了换流器触发环节异常、阀区故障时的故障特征以及换流器直流过压开路保护的动作特性。针对故障过程中组控、保护系统失去对换流器控制和保护功能的问题,分析了过程原因及保护动作逻辑,以期进一步完善控制保护系统对换流器不正常触发异常工况的风险识别和抵御能力。

The present work concerns a certain fault event,which occurred during Kun-Long mode operation at the LCC station of Kunliulong hybrid DC project,and in which the abnormal triggering and DC voltage drop of low-end converter induced overvoltage tripping of the high-end converter.The abnormal triggering of the converter,the characteristics of the valve area fault,and the activation characteristics of the DC overvoltage open-circuit protection are analyzed.With respect to the problem that the CCP control and protection system failed to control and protect the converter during the fault process,the causes and protection logic are discussed.This work may help to further improve the control and protection system's ability to identify and resist the risk of abnormal triggering of converters.