A Hybrid Modular Multilevel Converter Comprising SiC MOSFET and Si IGBT With Its Specialized Modulation and Voltage Balancing Scheme

In this article, a hybrid modular multilevel converter (MMC) topology is proposed, in which two of the submodules (SMs) are based on SiC mosfet , while others are based on Si IGBT. In the proposed hybrid topology, the capacitor voltage of SiC SM is controlled to be half of that of Si SM, which reduces the requirement for the blocking voltage of SiC mosfet . What is more, this article improves the modulation scheme to move most of the switching actions from Si SMs to the two SiC SMs, which strengthens the merits and avoids the shortcomings of SiC mosfet . Besides, to solve the voltage imbalance problem caused by the change of topology and modulation scheme, a specialized voltage balancing scheme is proposed. Finally, the simulation and experiment result proves the feasibility of the hybrid MMC and control scheme, and the comprehensive analysis verifies that the hybrid MMC can achieve a better balance among cost, loss, and feasibility compared with others.