Design and Testing of a Modular Multilevel Converter Submodule Based on 10 kV SiC MOSFETs

This paper focuses on the design and testing of a half bridge submodule based on discrete 10 kV/20 A SiC MOSFETs for a modular multilevel converter (MMC). The rated dc bus voltage of the submodule is 6.5 kV, and the MOSFETs switch with dv/dt up to 100 V/ns. Design considerations and challenges for components in the submodule are presented, especially the gate driver to support the robust continuous operation and the submodule voltage sensor. Systematic testing procedures are developed to fully test the submodule up to 6.5 kV. High voltage insulation and high dv/dt are tackled throughout the design and testing. The designed submodule is validated in the continuous switching test at 6.5 kV with dv/dt up to 100 V/ns.