Design for Reliability of SiC-MOSFET-Based 1500-V PV Inverters with Variable Gate Resistance

1500-V Photovoltaic (PV) inverters are becoming the mainstream in solar PV industry. Extending the maximum DC voltage from 1000 V to 1500 V can reduce the installation cost of PV power plants. However, it may negatively affect the reliability of the corresponding PV inverters, due to the increased loading stresses, i.e., voltage stress and thermal loading of power devices. In this context, this paper investigates the potential to enhance the reliability of SiC-MOSFET-based 1500-V PV inverters through the design of the gate resistance, considering the switching overshoot and the stray inductance in the commutation loops. The impact of switching speed on the inverter reliability is analyzed with the mission profile of a 125-kW/1500-V PV system (interfacing the grid with a SiC-based two-level inverter) installed in Denmark. The evaluation results indicate that the PV inverter with the proposed design (i.e., variable gate resistance) can achieve a better reliability performance than that with fixed gate resistance and ensure a safer operating voltage margin.