一种基于嵌套式全桥的新型混合MMC拓扑

Novel Hybrid MMC Topology Based on Embedded Full-Bridge

模块化多电平换流器(Modular Multilevel Converter,MMC)采用子模块级联方式,开关频率低、波形质量高、故障处理能力强,已成为当前柔性高压直流输电研究和应用的热点。基于半-全混合MMC的柔直系统可以有效清除直流侧故障,但全桥子模块在投资成本和稳态损耗上均需做出较大牺牲。为提高MMC的经济性,提出了一种包含嵌套式全桥阀段(Embedded Full-Bridge,EFB)的新型混合MMC拓扑,该阀段利用半桥整体翻转以对外输出负电平,可作为级联式全桥阀段的替代性方案。以一个简单仿真算例说明其工作原理,并在直流故障无闭锁穿越控制策略下的双端柔直系统中仿真验证了其故障清除能力。最后通过计算说明其相比传统半全混合MMC具备经济性优势。

The modular multilevel converter( MMC) has become a hot spot in the research and application of flexible HVDC transmission. It adopts cascaded submodules and features low switching frequency,high waveform quality and efficient fault-handling ability. The flexible HVDC system based on cell-hybrid MMC can effectively eliminate DC side faults,but the investment cost and steady loss of full-bridge submodules will increase. This paper proposes a new hybrid MMC topology with embedded full-bridge( EFB) valves,which can be an alternative for cascaded full-bridge valves for they can output negative level by fliping the whole half-bridge. This paper put its operating principle simply with a simple simulation numerical example and verified its fault-clearing ability by simulation in double-end flexible HVDC system with DC fault ride-through control strategy. As a result,the calculation proves its economic advantage compared with traditional cell-hybrid MMC.