直流电网中直流断路器失灵保护方案研究

针对基于模块化多电平换流器的柔性直流电网直流侧故障难以快速清除的问题,对基于MMC的柔性直流输电技术的基本原理和3种主流的直流侧故障隔离技术进行了研究。分析比较了3种高压直流断路器技术路线,选择混合式高压直流断路器作为清除柔性直流电网直流侧短路故障的方案,介绍了一种混合式高压直流断路器的基本结构和直流故障处理过程。参考交流电网断路器失灵保护策略,提出基于柔性直流电网的输电线路和母线上直流断路器失灵保护方案,并在PSCAD/EMTDC上搭建模型进行仿真验证。研究结果表明:所提出的断路器失灵保护方案在线路和母线上断路器未成功动作时使相邻断路器跳闸,实现故障的彻底隔离,并清除短路故障电流。

Scheme of failure protection for HVDC circuit breakers in MMC-HVDC grid

Aiming at solving the problem of fast DC-fault clearing in HVDC grid based on MMC ( MMC-HVDC ) , the principle of MMC-HVDC and three main isolation techniques of DC faults were studied. By comparing three technical routes of HVDC circuit breaker ( DC-CB) , the hybrid DCCB was used to interrupt DC faults. The topology and DC fault isolation process of a hybrid DCCB were studied. Refer-ring to the failure protection strategy in AC grid, a scheme of failure protection for HVDC circuit breaker in MMC-HVDC grid was proposed. A four-terminal MMC-HVDC grid was used to verify the feasibility of the proposed strategy in PSCAD/EMTDC platform. The results indicate that the proposed scheme can order adjacent DCCBS to interrupt DC faults completely and clear fault current if a DCCB fails to act.