一种具有故障隔离能力的MMC-HVDC换流站子模块拓扑研究

Fault-isolated sub-module topology of MMC-HVDC converter station

针对典型半桥型模块化多电平换流器(MMC)无法阻断直流短路故障电流的固有缺陷,提出一种串联型双电容箝位型子模块,并结合传统半桥型子模块,设计成混联型桥臂拓扑,采用更低额定工作电压的IGBT,实现子模块基本功能的同时,增加了故障电流隔离能力。与全桥子模块结构和箝位双子模块结构相比,所提出的子模块拓扑方案进一步降低了器件成本。详细描述了该方案故障电流阻断机理,并通过电磁暂态仿真模型验证了基于该子模块拓扑的换流站方案的可行性。

As the MMC（Modular Multilevel Converter） based on the typical half-bridge sub-module cannot block the fault current of DC short circuit,a series-type dual capacitor-clamped sub-module is proposed,which,combined with the traditional half-bridge sub-module,adopts the hybrid arm structure and applies the IGBT working at lower rated voltage to enhance the DC fault isolation capability while achieve the basic functions of MMC station. Compared with the topology of full-bridge sub-module or dual capacitor-clamped sub-module,the proposed sub-module topology further reduces the device cost. The mechanism of fault current blocking is described in detail and an electromagnetic transient simulation model is applied to verify the feasibility of the converter station scheme based on the proposed sub-module topology.