基于暂态能量流的MMC-HVDC电网故障限流器和接地方式综合优化

Comprehensive Optimization of Fault Current Limiter and Grounding Mode in MMC-HVDC Power Grid Based on Transient Energy Flow

直流短路故障电流的迅速上升,严重制约了基于半桥子模块的模块化多电平换流器高压直流(MMC-HVDC)电网在实际工程中的应用。从故障限流器和接地方式都是通过增大故障回路电阻或电感进行限流的本质出发,提出了基于暂态能量流的故障限流器和接地方式的综合优化方法。该方法以暂态能量流抑制率和抑制效率为目标函数,以故障限流器、接地方式和中性线电抗为优化变量构建最优化模型。以四端双极型MMC-HVDC电网为例,在PSCAD/EMTDC仿真系统中对直流侧单极接地故障条件下的故障限流器和接地方式进行优化设计。结果表明,所选参数能够有效降低直流故障电流和桥臂电流,同时兼顾健全极过电压约束,为直流电网的故障限流器、接地方式和中性线电抗的多参数综合优化配置提供参考。

The application in the practical engineering of modular multilevel converter based high voltage direct current(MMCHVDC)power grid based on half bridge submodules has been seriously restricted by the rapid increasement of DC short-circuit fault current.From the essence that the fault current limiter and grounding mode limit the current by increasing the fault circuit resistance or inductance,a comprehensive optimization method of fault current limiter and grounding mode based on transient energy flow(TEF)is proposed.This method takes the TEF suppression rate and suppression efficiency as the objective functions,and takes the fault current limiter,grounding mode and neutral reactance as the optimization variables,to construct the optimization model.Taking the four-terminal bipolar MMC-HVDC power grid as an example,the fault current limiter and grounding mode under single-pole-to-ground fault conditions on the DC side are optimized in PSCAD/EMTDC simulation system.The results show that the selected parameters can effectively reduce the DC fault current and bridge arm current,and provide a reference for the multi-parameter comprehensive optimal configuration of fault current limiter,grounding mode and neutral line reactance of DC grid considering the overvoltage constraints of normal poles.