Comparison of GaN and SiC power devices in application to MW-scale quasi-Z-source cascaded multilevel inverters

Wide bandgap (WBG) semiconductors including gallium nitride (GaN) and silicon carbide (SiC) offer significant performance improvement compared with conventional silicon power devices. The quasi-Z-source cascaded multilevel inverter (qZS-CMI) provides many advantages over the conventional CMI while applied in photovoltaic (PV) systems. In this paper, two solutions are proposed and compared to the design goal of a high efficiency and low-cost qZS-CMI based 1 MW/11 kV PV system. The first solution is based on 650 V GaN enhancement mode high-electron-mobility transistors (E-HEMT) and 650 V SiC Schottky diodes. The second solution uses 1200 V SiC power modules and 1200 V SiC Schottky diodes. The power losses and costs of the two candidate designs are compared in details. It is concluded that the first solution shows lower power losses and costs per quasi-Z-source inverter (qZSI) module. However, due to the low voltage rating of GaN E-HEMTs, more qZSI modules are needed to achieve the overall 11 kV inverter rating. Therefore, the second solution shows lower total power loss and cost in the medium-voltage, MW-scale qZS-CMI PV system.