天广直流换流阀异常导通EMTDC仿真分析

Analysis on the abnormal breakover of the converter valve based on EMTDC simulation in Tian-Guang HVDC project

自2014年7月以来,天广直流发生了四次换流阀异常导通事件,造成主设备过电流或过电压,严重影响天广直流安全稳定运行。为查明换流阀异常导通原因,从极控系统、VBE系统、换流阀及其组件、TE板等方面开展理论分析、现场排查、仿真分析、物理试验,成功排除了极控系统、VBE系统、换流阀及其组件导致换流阀异常导通的可能性。通过TE板BTC回路分析以及加压试验,发现了TE板在高污高湿条件下误触发晶闸管的情况。在BTC动作门槛值与TE板异常个数关系分析的基础上,开展四次换流阀异常导通事件的EMTDC仿真分析,模拟了部分TE板BTC动作门槛值降低的情况,得到了与现场故障波形高度相似的仿真波形。结果表明即使部分阀片TE板表面较为清洁,其余TE板表面积污严重,在潮湿环境下也可以导致换流阀异常导通。

Since July 2014, Tian-Guang HVDC project happened the events of the converter valve abnormal breakover four times, which caused the main equipment overcurrent or overvoltage and seriously influenced the safe and stable operation of Tian-Guang HVDC project. In order to identify the cause of the converter valve abnormal breakover, the theoretical analysis, field checking, simulation analysis and physical test are done from the aspects of the control system, the VBE system, the converter valve and its components and the TE boards, which successfully eliminates the possibility of the converter valve abnormal breakover by the control system, VBE system, converter valve and its components. Through the analysis and high voltage test of the BTC circuit of the TE boards, it is found that the TE boards will mis-trigger the thyristor under the high pollution and humidity condition. Based on the analysis of the relationship of the BTC acting threshold and the number of the abnormal TE boards, the decrease of the threshold of the partial BTC is set in the EMTDC simulation on the four events, and the simulation waves are highly similar to the field fault waves. The results show that even if part of TE boards are clean and the rest are polluted seriously, the TE boards also would lead to the abnormal breakover of the converter valve in the humid environment.