考虑故障阀臂封锁条件下的VSC-HVDC换流器故障诊断算法

针对两电平柔性直流输电(VSC-HVDC)系统换流器内部常见的IGBT阀器件短路失效、桥臂直通、交流侧单相接地、交流侧两相短路、直流单极接地这5类贯穿故障,研究了换流器故障保护与诊断的协调配合方案,分析了保护闭锁条件下系统直流电压及交流电流的变化规律,据此提出了利用闭锁时刻的直流电压及闭锁后2个周期的三相交流电流作为特征信号进行换流器故障分类与定位的诊断方法,并确定了用于区分故障类型的电压、电流诊断阈值。对换流器严重贯穿故障进行仿真,利用PSCAD/EMTDC模型对所提出的诊断方法进行了验证,结果表明该方法不仅能可靠识别故障类型,还能准确定位故障位置,可用于故障阀臂闭锁条件下VSC-HVDC换流器的故障诊断。

Fault diagnosis algorithm for converter of VSC HVDC system with failed valve arm blocking

According to five types of ordinary penetrating faults inside the converter of VSC-HVDC system, including short circuit failure of IGBT valve device, bridge straight-through fault, AC-side single-phase grounding fault, AC-side two-phase short circuit fault and DC-side monopole grounding fault, the coordination scheme of fault protection and fault diagnosis for converter is studied. Based on analyzing the system change rules of DC voltage and AC current under the condition of blocking protection, a fault diagnosis algorithm for fault classification and location of converter is proposed, which takes the DC voltage at blocking time and three-phase AC current during two cycles after blocking time as the characteristics signals. Moreover, the voltage and current thresholds for fault classification are determined. A VSC-HVDC system model built in PSCAD/EMTDC is used to validate the proposed fault diagnosis method by simulating serious penetrating faults inside the converter. The simulative results prove that the proposed method can not only identify fault type reliably, but also locate fault position accurately, which is suitable for fault diagnosis for the converter of VSC-HVDC system under the condition of failed valve arm blocking.