具备直流故障自清除能力的新型子模块拓扑

Novel Sub-module Topology with DC Fault Self-clearance Capability

基于模块化多电平换流器MMC(modular multilevel converter)的高压直流输电系统发展前景广阔,而传统的半桥结构MMC 子模块故障穿越能力较低。为此,首先提出一种具有直流故障自清除能力的子模块拓扑,该拓扑在直流侧故障时可利用反向接入子模块的电容电压来阻断二极管的导通,切断故障电流通路;其次分析比较了几种常见的具有自清除能力的拓扑在建造投资和运行损耗方面的成本;最后,为便于对已建成工程进行改造,提出了新型子模块拓扑的控制调制策略。基于PSCAD 电磁暂态仿真软件验证了所提结构的正确性和有效性。

The development prospect of high voltage direct current transmission system based on modular multilevel converter(MMC)is broad. However,the traditional half-bridge MMC sub-module has a lower fault ride through capability. Accordingly,a sub-module topology with DC fault self-clearance capability is proposed at first,which can block the conduction of the diode and cut off the fault current path using the capacitance voltage of reverse access sub-modules under DC fault. Second,the costs of construction and operation loss of several common topologies with fault selfclearance capability are analyzed and compared. Finally,to facilitate the transformation of completed projects,a modulation control strategy for the novel sub-module topology is proposed. The correctness and effectiveness of the proposed topology are verified based on PSCAD electromagnetic transient simulation software.