低压直流母线AC-DC电力电子变压器及其短路故障穿越方法

传统的基于半桥型模块化多电平电力电子变压器使用大量的开关器件和无源元件,限制了其功率密度和效率的提高。提出了一种组合全桥型模块化多电平换流器(MMC)和输入侧间接串联型输入串联输出并联DC-DC变换器的电力电子变压器拓扑,MMC输出等级较低的中压直流母线,可减少隔离级DC-DC模块数量,且可以实现故障时的自阻断功能。通过改变DC-DC变换器模块输入侧的串联连接方式,可有效避免中压直流端口短路时导致DC-DC变换器输入侧电容短路问题。该电力电子变压器拓扑同时具备中压和低压直流端口,且可以有效降低开关器件、无源元件、高频变压器以及DC-DC变换器模块数量,提高电力电子变压器的功率密度、效率和故障穿越能力。最后基于MATLAB/Simulink,搭建了该电力电子变压器的仿真模型,仿真结果验证了该拓扑的可行性。

AC-DC Power Electronic Transformer with Low-voltage DC Bus and Strategy of Short-circuit Fault Ride-through

The traditional power electronic transformer(PET)based on modular multilevel converter(MMC)with half-bridge submodule uses a large number of switching devices and passive components, which limits its power density and efficiency. A topology of PET based on MMC with H-bridge submodule and input series output parallel(ISOP)DC-DC converter is proposed, which can generate a low level medium-voltage DC bus to reduce the number of DC-DC modules and realize self-blocking when a fault occurs. An indirect series of ISOP converter structure is proposed, when the medium voltage DC port is short-circuit, the short-circuit discharge of the input side capacitor of DC-DC converter can be effectively avoided by changing the connection mode of the input side of DC-DC converter. The numbers of switching devices, passive components, high-frequency transformers and DC-DC converter modules can be effectively reduced, and the power density, efficiency and fault ride-through ability can be effectively improved by the proposed PET. Finally, the simulation model of the proposed PET is built based on MATLAB/Simulink, and the feasibility of this topology is verified by the simulation results.