Active Voltage Balancing of Series Connected SiC MOSFET Submodules Using Pulsewidth Modulation

Series connection of multiple transistors is an attractive solution to achieve higher voltage capability. However, the voltage imbalance among the series-connected devices is a critical issue caused by mismatches of device characteristics and gate signals. To prevent the failure of devices from the voltage imbalance, voltage balancing control (VBC) is required. In this work, an active VBC for series-connected silicon carbide (SiC) mosfet submodules is proposed with a pulsewidth modulation (PWM) method. A submodule consists of two switches and one shunt capacitor, and the PWM method actively controls the capacitor voltages for balancing. The proposed VBC is simulated in MATLAB/Simulink and experimentally verified with six series-connected SiC mosfet submodules at up to 150 kHz. The voltage balancing is achieved within 3.9% of the targeted balanced voltage.