基于钳位子模块的开关对复用型模块化多电平固态变压器

Modular multi-level converter solid-state transformer based onthe clamped switch pair integrated submodule

基于模块化多电平换流器的固态变压器(modular multi-level converter based solid-state transformer,MMC-SST)由于具备多电压等级、多电压形态的端口,在交直流混合配电网中得到广泛关注。双向有源全桥(dual active bridge,DAB)变换器型MMC-SST存在功率密度低、成本高等问题,且传统半桥结构的DAB型MMC-SST在中压直流(medium voltage direct current,MVDC)端口短路故障情况下无法清除故障电流,限制了其在配电网中的应用;传统全桥结构的DAB型MMC-SST虽具备故障阻断能力,但同时也增加了开关管数目。文中基于混频调制原理,对传统DAB型MMC-SST的拓扑进行改进,提出基于钳位子模块的开关对复用(clamped switch pair integrated submodule,CSPI)型MMC-SST拓扑,该拓扑与传统半桥、全桥结构的DAB型MMC-SST拓扑相比,不仅节约了开关器件,还使得SST具备MVDC短路故障清除能力,极大地提高了DAB型MMC-SST的功率密度和供电可靠性。通过理论分析与仿真模拟,验证了所提CSPI型MMC-SST拓扑及频率解耦方法的可行性。

Modular multi-level converter based solid-state transformer(MMC-SST)has gained wide attention in AC-DC hybrid distribution network due to the availability of ports with multiple voltage levels and voltage patterns.Dual active bridge(DAB)-type MMC-SST has problems such as low power density and high cost,and the tradition-al half bridge structure of DAB-type MMC-SST has failure to clear fault current in case of short-circuit faults at me-dium voltage direct current(MVDC)ports,which affects its application in distribution network.Although full bridge structure of DAB-type MMC-SST has fault blocking capability,it also increases the number of switches.Improve the topology of the traditional DAB-type MMC-SST,then a clamped switch pair integrated submodule(CSPI)-type MMC-SST topology is proposed based on the principle of frequency mixing modulation.The proposed topology not only reduces the number of switching devices but also makes the SST have the capability of clearing MVDC short-circuit faults,as compared to the traditional half bridge and full bridge DAB-type MMC-SST topologies.The power density and power supply reliability of the DAB-type MMC-SST are greatly improved by the proposed topology.The feasibility of the proposed CSPI-type MMC-SST topology and frequency decoupling method is verified through theoretical analysis and simulation.