A SiC MOSFET and Si IGBT Hybrid Modular Multilevel Converter With Specialized Modulation Scheme

The utilization of silicon carbide (SiC) MOSFET instead of silicon (Si) IGBT can significantly improve the performance of many converters. However, a modular multilevel converter (MMC) completely based on the SiC MOSFET suffers from high cost and high conduction loss at the high power levels. To solve these issues, a SiC MOSFET and an Si IGBT hybrid MMC are proposed in this letter. In the new topology, only one full-bridge submodule (SM) of each arm uses SiC MOSFETs, while the other half-bridge SMs use Si IGBTs. Meanwhile, a specialized modulation scheme is proposed to move most of the switching actions from the Si SMs to the SiC SM. As a result, the advantages of SiC MOSFET and Si IGBT are both utilized, and the total loss and cost of the MMC are reduced. Finally, the experimental result proves the feasibility of the topology and modulation scheme, and the further loss analysis verifies the superiority of the hybrid MMC over others.