Abstract: This paper proposes to achieve an high step-down ratio by using MMC DC-DC converter topology and maintaining high conversion efficiency with high power rating. For High step down ratio dc-dc power conversion power electronics transformers are can be used. This arrangement requires a large number of high isolation voltage transformers and complicated balancing control. To overcome this drawback the solution is inherent voltage balancing, this paper introduces a new MMC topology for dc-dc conversion. Depending on the number of sub modules the MMC achieves high-voltage step-down ratio. With no necessary requirement of high-voltage isolation transformers the converter exhibits simplicity and scalability by using Digital switching, the converter operating frequency is high compared to the switching frequency. The operation principle and theoretical analysis are presented in this paper.

Keywords: Modular multilevel converter (MMCs), phase-shift control, step-down ratio, resonant converter, DC-DC conversion.