Switched-Capacitor-Based Seven-Level Boosting Inverter With Reduced Voltage Stress for Grid-Connected Photovoltaic Applications

This article proposes a seven-level common-ground-type (CGT) transformerless inverter with a boosting feature for solar photovoltaic (PV) applications. The proposed topology's common ground feature eliminates the crucial ground leakage current caused by the varying common mode voltage in grid-connected PV inverters. Unlike the conventional and recent CGT inverters, the proposed inverter requires only two capacitors of voltage rating lower than the inverter's peak output voltage. Thereby, the semiconductor devices experience reduced voltage stress resulting in lower power losses. Further, the circuit description and operating principle are presented in detail. The detailed comparative assessment of the proposed and its counterpart topologies is carried out to highlight the superior features of the former such as lower component count, least average number of conducting devices, fewest number of devices in the charging path, self-voltage balancing of the capacitors and reduced capacitor voltage diversity factor. In addition, it will be shown that the proposed inverter cost and footprint requirements are lesser than the available competent solutions. Furthermore, a detailed reliability assessment with fault tolerant operation is presented. Finally, the experimental results of the proposed inverter's grid-connected and stand-alone operations are elucidated to validate its feasibility.