Active Gate Driver for SiC-MOSFET-Based PV Inverter With Enhanced Operating Range

For photovoltaic (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 of a power device. 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 converters. During a cloudy day when the inverter has to operate at PV panels open-circuit voltage, it becomes harder to push higher reactive power support to the grid due to the current derating of the SiC-devices at the operating dc bus voltages to keep the device within its safe operating limits with low switching losses at all operating conditions. Slowing down the switching transient could be a remedy but this also increases the converter losses. This paper demonstrates an application of a dynamic gate resistance modulation technique to keep the SiC-device within its safe operating limits while maintaining a low switching loss with minimum voltage and current overshoots. This helps to inject more power to the grid with at higher dc bus voltages without enhancement of the thermal management system. The proposed implementation also works equally well at high junction temperatures (up to $T_j = 150$ °C), which further increases the operating range of the PV inverter.