High efficiency cascaded quasi-z-source photovoltaic inverter module using eGaN FETs

This paper presents a single-phase grid-connected photovoltaic (PV) module-integrated converter (MIC) based on cascaded quasi-Z-source inverters (qZSI). In this system, each qZSI module serves as a MIC and is connected to one PV panel. Due to the cascaded structure and qZSI topology, the proposed MIC features low voltage gain requirement, single-stage energy conversion, enhanced reliability and good output power quality. Furthermore, the enhancement mode Gallium-Nitride field effect transistors (eGaN FETs) are employed in the qZSI module for efficiency improvement at higher switching frequency. Detail design of the qZSI module is performed based on the derived ac equivalent model and power loss analytical model. As a result, the number of cascaded modules and the inverter switching frequency are optimized. The parameters of the quasi-Z-source network are designed. A 250W, 25-50V input qZSI module is built using the optimization procedure. A 98.06% peak efficiency of the power module is achieved at 45V and 140W input.