PWM Converter Integrating Voltage Equalizer for Photovoltaic Panels under Partial Shading

Abstract

Partial shading on a photovoltaic (PV) panel comprising of multiple substrings connected in series leads to major issues, such as decreased power generation and occurrence of multiple power point maxima. Various PV equalizers have been proposed to preclude partial shading issues. However, system complexity increases because of the addition of PV equalizers, and circuits are prone to complexity because each PV equalizer contains switches. This study proposes a single-switch PWM converter integrating a PV equalizer using a series-resonant voltage multiplier (SRVM) for PV panels under partial shading. A PWM converter and PV equalizer can be integrated into a single unit, which decreases the switch count, achieving system- and circuit-level simplifications. Detailed operation analysis was performed for the SRVM, using which a dc equivalent circuit was mathematically derived. Experimental tests using a prototype for three substrings connected in series were performed with solar array simulators. The integrated converter successfully precluded the occurrence of multiple power point maxima and significantly improved the extractable maximum power as compared to that without equalization, demonstrating its efficacy.