MMC with Parallel-connected MOSFETs for LVDC Distribution Networks

A highly efficient DC-AC converter is key to the success of low-voltage DC (LVDC) distribution networks. Calculated power losses in a conventional IGBT 2-level converter, a SiC MOSFET 2-level converter, a Si MOSFET modular multilevel converter (MMC) and a GaN HEMT MMC are compared. Calculations suggest that the parallel-connected Si MOSFET MMC may be the most efficient topology for this LVDC application. In this paper, the current unbalance limits for the parallel-connected MOSFETs and the optimal number of parallel-connected MOSFETs for MMC are investigated. Experimental results are presented for current sharing in parallel-connected MOSFETs and for the verification of power loss in a single Si MMC module.