基于改进型模块化嵌入式多电平换流器拓扑的HVDC直流故障清除策略

HVDC DC fault clearing strategy based on improved MEMC topology

目前,已有的高压柔性直流输电工程大多都采用包含半桥子模块的模块化多电平换流器(MMC),但是半桥型MMC缺乏直流故障清除能力。为解决这一问题本文在原来模块化嵌入式多电平换流器(MEMC)拓扑的基础上提出了改进型MEMC拓扑,该拓扑具有更高的可靠性和功率处理能力,并提出了一种控制技术,用全桥子模块产生的负电压对功率因数滞后的负载进行晶闸管的强制换相。改进型MEMC除具有直流故障清除能力外,还提供了更宽的工作范围和更小的子模块电容器尺寸。最后在PSCAD/EMTDC中搭建改进型MEMC-HVDC模型,并进行直流故障仿真,仿真结果验证了该拓扑的适用性和直流故障清除能力。

At present,most of the existing high-voltage flexible DC transmission projects use modular multilevel converters(MMC)including half-bridge submodules,but half-bridge MMC lacks the ability to clear DC faults.In order to solve this problem,this paper proposes an improved MEMC topology based on the original MEMC(module embedded multilevel converter)topology,which has higher reliability and power handling capability,and proposes a control technology that uses The negative voltage generated by the sub-module performs forced commutation of the thyristor on the load with lagging power factor.In addition to the DC fault clearing capability,the improved MEMC also provides a wider operating range and a smaller sub-module capacitor size.Finally,an improved MEMC-HVDC model is built in PSCAD/EMTDC,and a DC fault simulation is carried out.The simulation results verify the applicability of the topology and the DC fault removal capability.