A quasi zero-current-switching DC/DC Modular-Multilevel Converter (MMC) with LCL circuit for DC grids

A DC/DC Modular-Multilevel Converter (MMC) is proposed in this paper, in which two modular multilevel converters are linked by a LCL tank. With the proposed converter, the high power medium frequency transformer can be eliminated to simplify the structure, quasi zero-current-switching operation of both MMCs can be achieved to alleviate the switching loss, the voltage stress of internal LCL tank can be controlled and the destructive voltage derivation applying on LCL tank can be avoided. The operations, modulations and parameter design are given in this paper. A simulation model in Matlab/Simulink and a low power prototype are built to validate the proposed topology.