Active gate driver for SiC MOSFET based PV inverter with enhanced operating range

Abstract

For photo-voltaic (PV) inverter applications, the grid code mandates reactive power support to the grid, and the amount of reactive power injection may be limited by the voltage overshoot during the switching transients. For SiC-MOSFET based PV inverters this problem is more pronounced since the voltage and current gradient during switching transitions are much higher than a Si-based power devices. During a gloomy day when the inverter has to operate at PV panel's open circuit voltage, it becomes harder to push higher currents through the device but also keeping the device within its SOA and low the switching loss at all operating conditions. Slowing down the switching transient could be a remedy but this also increases the converter switching loss. This paper demonstrates an application of dynamic gate resistance modulation technique to keep the SiC-device inside its safe operating area (SOA) while maintaining a low switching loss with minimum voltage and current overshoots. The proposed implementation is verified with hardware test results at high junction temperatures (up to 150°C).