Current Equalization in Photovoltaic Strings With Module Integrated Ground-Isolated Switched Capacitor DC–DC Converters

Abstract

A ground-isolated switched capacitor (SC) dc-dc converter-based current equalization scheme for partially shaded photovoltaic (PV) strings of a grid-connected system is presented. SC converters are compact, light, and have very high efficiency even for a wide variation in load under certain operating conditions. These features make them ideal for integration with the PV module for current equalization. The factors affecting the maximum output power that the SC converter can deliver, the limiting value of the maximum output power, and efficiency issues of the SC converter are studied. These studies are required to optimize the design of the equalizing SC converter and to maximize its efficiency. A novel algorithm that utilizes the results of the aforementioned analysis to maximize the net power available due to the SC converter-based current equalization scheme for grid-connected applications is proposed. Experimental results showing the advantages of current equalization with SC converters as compared to that with conventional dc-dc converters are presented.