MMC-HVDC系统换流器桥臂短路故障暂态特性分析

桥臂短路故障是模块化多电平换流器型高压直流输电(MMC-HVDC)系统中的严重故障。在换流器不闭锁和闭锁这2种情况下对桥臂短路故障的暂态特性进行分析:针对换流器不闭锁的情况,对两端换流器的桥臂电气量暂态特性进行较为全面的阐述,重点分析了桥臂短路电流的组成;针对换流器的闭锁情况,建立了桥臂短路电流通路的电路模型,推导了桥臂短路电流的解析表达式,分析了系统交直流侧电压电流的动态变化过程并给出了桥臂短路故障的保护配置方案。基于PSCAD/EMTDC搭建双端MMC-HVDC仿真模型,仿真结果验证了理论分析的正确性和保护配置的有效性。对桥臂短路故障暂态特性进行分析可为MMCHVDC系统换流器保护区的保护配置方案提供参考。

Transient characteristic analysis of converter bridge arm short circuit fault in MMC-HVDC system

Bridge arm short circuit is a severe fault in MMC-HVDC(Modular Multilevel Converter based High Voltage Direct Current) system. Transient characteristics of bridge arm short circuit fault are analyzed when the converter is unblocked or blocked. Aiming at the case that the converter is unblocked, the transient characteristics of bridge arm electrical quantity of the converter at both ends are given, and the composition of the bridge arm short circuit current is analyzed. For the other case that the converter is blocked, the circuit model of bridge arm short circuit current is established. Meanwhile, the analytical equation of bridge arm short circuit current is deduced, and the dynamic variations of voltage and current on AC and DC side are analyzed. The protection configuration scheme of bridge arm short circuit fault is also given. A two-terminal MMC-HVDC simulation model is built based on PSCAD/EMTDC. The simulative results validate the correctness of transient characteristic analysis and the effectiveness of the protection configuration. The transient characteristic analysis of the bridge arm short circuit fault can provide references for converter protection strategies of MMC-HVDC system.