一种能够阻断直流故障电流的新型子模块拓扑及混合型模块化多电平换流器

A New Topology of Sub-modules With DC Fault Current Blocking Capability and a New Type of Hybrid MMC Converter

针对常规半桥型模块化多电平换流器无法隔离直流故障电流的问题,提出一种新型的应用于模块化多电平换流器的自阻型子模块拓扑,并列出自阻型子模块的4种结构。这4种类型的自阻型子模块在隔离直流故障电流时,需要同时闭锁IGBT的触发脉冲。为了降低触发同时性的要求,进一步提出无需同时闭锁IGBT触发脉冲的2种增强自阻型子模块拓扑。模块化多电平换流器技术(modular multilevel converters,MMC)的全部子模块采用增强型子模块时所使用的电力电子器件较多,为了进一步减少MMC中电力电子器件的数量,提出一种由增强型子模块和常规半桥子模块构成的混合型MMC。PSCAD/EMTDC下的仿真研究表明,所提出的自阻型子模块、增强型子模块及混合型换流器能有效隔离直流故障。相比于常规半桥型MMC,该混合型MMC仅需提高25%的IGBT即可具备隔离直流故障电流的功能,因此具有良好的工业应用价值。

To solve the problem that traditional MMC based on half-bridge sub-module being incapable of isolating dc fault current, a new topology of self-blocking sub-module is proposed in this paper. Four types of self-blocking sub-modules that require simultaneously blocking the IGBTs are firstly proposed. To eliminate the requirements on simultaneously blocking, two types of enhanced self-blocking sub-modules are further proposed. To further reduce the used power electronic devices, a hybrid converter combines enhanced self-blocking sub-modules with traditional half bridge sub-modules is then proposed. Feasibility of the proposed sub modules and hybrid converter are verified by simulations in PSCAD/EMTDC. The proposed hybrid converter is able to isolate dc fault current with only 25% increase of the used power electronic device compared with traditional half-bridge cell MMC which is not able to isolate dc fault current.