A Unified Modular Multilevel DC/DC Converter Structure with Flexible AC Power Transfer Controls

This paper classifies non-isolated DC/DC converters utilizing modular multilevel converters (MMC) into two broad classes based on the two possible AC power transfer mechanisms in the absence of an intermediate transformer. A unified DC MMC (UDCMMC) is proposed to demonstrate that existing MMC-based DC/DC converters of both classes can be realized through a general structure and a common control strategy. The UDCMMC also realizes a new topology that is potentially more cost-efficient than existing topologies within a range of DC/DC voltage conversion ratios. The operation of the UDCMMC with both mechanisms of AC power transfer is verified in PLECS simulation.