采用双电流转移支路的直流电网故障清除策略

Fault Clearing Strategy of DC Power Grid with Double Current Transfer Branches

为了解决模块化多电平换流器直流故障难以清除的问题,论文提出了一种采用双电流转移支路的直流电网故障清除策略。该策略通过在换流器直流侧增加双电流转移支路和能量耗散支路,使故障期间的故障电流被迫转移到这两个支路中,保证在低压小电流情形下断开故障线路,并可在故障隔离之后迅速恢复电网的正常运行。双电流转移支路安装在直流母线上,采用晶闸管与电容配合的方式起到转移换流器电容放电能量的作用;能量耗散支路安装在直流出线上,通过接地电阻消耗线路电感储存的能量。最后,通过PSCAD/EMTDC验证了所提策略在故障清除和恢复运行方面较优的性能,并与其他直流断路器方案进行对比,体现了其在器件成本和器件数量方面良好的经济性。

In order to solve the problem of clearing the DC fault of modular multilevel converter(MMC),we put forward a fault clearing strategy of DC grid with double current transfer branches.In the strategy,by adding double current transfer branch and energy dissipation branch to the DC side of the MMC,the fault current is forced to both branches during the failure,so that the fault line can be disconnected at low voltages and small currents,and the DC grid can be quickly restored after fault isolation.The double-current transfer branch is installed on the DC bus,where the thyristor and capacitor are utilized to play the role of transferring the discharge energy of the converter capacitor,and the energy dissipation branch is installed on the DC line,which consumes the energy stored by the line through the ground resistance.Finally,PSCAD/EMTDC verifies the superior performance of the proposed strategy in fault removal and recovery,and its good economy in terms of device cost and number compared with other DC circuit breakers.