Switched-capacitor converter for PV modules under partial shading and mismatch conditions

Partial shading and mismatch among the Photovoltaic (PV) modules is an important issue, which decreases the harvested power from the PV modules, and causes an efficiency problem for renewable energy systems. Several power electronics topologies that allow charge redistribution between the PV modules, have been proposed to balance PV modules which are connected in series. Differential Power Processing (DPP) is a technique which improves the overall efficiency of the power balance system by processing only a fraction of the module power. In this study, the power loss analysis of the switched-capacitor (SC) converter, which is configured in ladder architecture with the PV sub-modules for power balancing purpose, is derived and verified by simulation and experimental works. The proposed loss model predicts the percentage of power loss of the SC converter working under arbitrary partial shading conditions. Switched-Capacitor converter prototype was built and tested using a 140 W photovoltaic module. It is found that for 0-25% overall partial shading the overall efficiency remains above 98%. The experimentally obtained loss is in reasonable agreement with its theoretical counterpart.