具备故障电流对称清除能力的双向开关钳位式全桥子模块

Bidirectional Switch Clamp Full Bridge Submodule With Fault Current Symmetrical Clearing Capability

实现对直流侧故障的快速隔离与穿越是基于模块化多电平换流器(modular multilevel converter,MMC)的直流输电系统亟需解决的问题。在对现有子模块进行归纳与改进的基础上,提出了一种双向开关钳位式全桥子模块(bidirectional switch clamped full bridge sub-module,BCFSM),该子模块具备直流短路故障电流对称清除能力,闭锁后可引导故障电流对桥臂内所有电容进行串联充电,从而快速清除故障电流并保证闭锁期间桥臂内电容电压的均衡。同时,由于双向开关兼具钳位与旁路通道作用,与其他具备故障穿越能力的子模块相比,BCFSM具有良好的经济性。基于MATLAB/Simulink的仿真结果表明,BCFSM-MMC可快速清除直流短路故障电流,且能够快速重启,具有高直流故障穿越可靠性的同时降低了换流站的建造与运行成本。

The rapid isolation and ride-through of the DC side faults is required urgently for DC transmission systems based on the modular multilevel converter(MMC).Based on the induction and improvement of the existing sub-modules,this paper proposes a bidirectional switch clamped full bridge sub-module(BCFSM)with DC fault current symmetrical clearing capability.After blocking,the DC fault current is led to charge all capacitors in the bridge arm in series,which ensures both the fast fault current clearing and the excellent capacitor voltage balance in the bridge arm during blocking.Meanwhile,compared the fault ride-through capabilities with other sub-modules,BCFSM performs better in terms of economy because the bidirectional switch has the function of both clamping and bypass channel.Simulation results based on MATLAB/Simulink show that BCFSM-MMC is capable of fast DC fault current clearing and fast restart after fault clearing,which improves the reliability of DC fault ride-through while reducing the cost of converter construction and operation.