Evaluation of 1.2 kV SiC MOSFETs in multilevel cascaded H-bridge three-phase inverter for medium-voltage grid applications

A study is conducted to evaluate 1.2 kV silicon-carbide (SiC) MOSFETs in a cascaded H-bridge (CHB) three-phase inverter for medium-voltage applications. The main purpose of this topology is to remove the need for a bulky 60 Hz transformer normally used to step up the output signal of a voltage source inverter to a medium-voltage level. Using SiC devices (1.2-6.5 kV SiC MOSFETs) which have a high breakdown voltage, enables the system to meet and withstand the medium-voltage stress using only a minimal number of cascaded modules. The SiC-based power electronics when used in the presented topology considerably reduce the complexity usually encountered when Si devices are used to meet the medium-voltage level and power scalability. Simulation and preliminary experimental results on a low-voltage prototype verifies the nine-level CHB topology presented in this study.