Simple Control Strategies for dv/dt Reduction in SiC MOSFET based Modular Multilevel Converters

This paper proposes a simple control strategy for the dv/dt reduction in the modular multilevel converters (MMCs) based motor drives. In particular, the control strategy aims at the reduction of the MMC output voltage slew rate by coordinating the switching transients of several submodules. It is realized via utilizing extra submodules or simply applying a delay time to the switching transients. Both methods are implemented without affecting the switching speed of the power devices. Thus, the methods could mitigate the drawbacks caused by the high dv/dt while maintaining the advantages brought about by the fast switching speed of the silicon carbide (SiC) devices. The simulation results and test results based on a SiC MMC are provided. It is shown that the proposed control methods bring down the output dv/dt by around 50 %.