柔性直流输电系统中IGBT阀的故障诊断方法

Research on the Fault Diagnosis of IGBT Valve in VSC-HVDC

基于两电平VSC-HVDC系统拓扑图,分析了IGBT阀开路故障时交流侧三相电流的变化情况,得到了故障相电流直流分量的变化规律,进而研究了系统传输功率突变对三相交流电流基波分量相位的影响,从而提出一种运算简便且快速的故障阀定位方法。该方法首先根据各相电流基波分量相位差判断系统状态,在排除功率突变的前提下再以直流分量标幺值为诊断变量对故障元件进行定位。最后模拟系统潮流反转后某IGBT阀发生失效开路故障的情况,利用所提出的方法进行故障诊断,结果表明该方法可快速准确的确定故障位置,并能避免因功率突变而引起的误诊问题。

Open-circuit failure of IGBT valve in voltage sourced converters based high voltage direct current(VSC-HVDC) system may lead to abnormal operation of converters, and the research on its fault diagnosis has great significance for the safety and reliability of the whole system. In this paper, based on two-level VSC-HVDC, three-phase current at alternating side when open-circuit fault occurs in IGBT valve is analyzed. The variation law of direct current component in fault phase is obtained. Furthermore, the influence of transmission power saltation on fundamental component of three-phase alternating current is studied. Accordingly, a simple and high-speed locating method for fault switch is put forward. According to the phase difference of fundamental component of each phase current, the method determines the system state at first. On the premise of excluding power mutation, the per-unit value of direct current component is used as diagnostic variable to locate fault power switch. Finally, the condition that open-circuit fault occurs in a IGBT valve after power flow reversal is simulated, and the diagnosis is conducted with the proposed method. The results show that the method presented in this paper not only locates rapidly and accurately the faults location, but also avoids misdiagnosis caused by power mutation.