A Three-Phase Multiplexing Arm Modular Multilevel Converter With High Power Density and Small Volume

Modular multilevel converter (MMC) faces challenges ofcost and footprint in medium and high voltage grid applications. By adding a three-phase switching bridge on the basis of MMC, this article proposes a three-phase multiplexing arm modular multilevel converter (TPMA-MMC) with high power density and small volume. The multiplexing principle for TPMA-MMC is investigated, showing the multiplexing arm can be multiplexed for one-third fundamental period. After that, the subsection modulation scheme is further proposed for energy balance purpose. Compared with MMC, the number of submodules (SMs) and power devices are reduced by 22.8% and 13.83%, respectively, resulting in lower construction cost. Meanwhile, the SMs’ capacitance and the total capacitor energy storage of TPMA-MMC reduce greatly with the subsection modulation, which can greatly reduce the footprint and improve the power density. Moreover, the proposed TPMA-MMC outperforms the MMC in terms of efficiency. Finally, the topology and proposed modulation scheme are verified by simulation and experimental results.