Single-switch PWM converter integrating voltage equalizer for photovoltaic modules under partial shading

A photovoltaic (PV) string comprising multiple modules/sub-modules connected in series is well known to suffer from partial shading issues, such as decreased power generation and the occurrence of multiple power-point maxima. Although various kinds of differential power processing converters and voltage equalizers that can preclude partial-shading issues have been proposed, increases in circuit and system complexities are very likely due to the increased switch count and added converters. In this paper, a single-switch PWM converter integrating a voltage equalizer for PV modules under partial shading is proposed. In the proposed integrated converter, since the converter and voltage equalizer are integrated into a single unit without increasing the switch count, both the system level and circuit level simplifications are feasible. Experimental equalization tests emulating partially shaded conditions were performed using a prototype built for the four PV modules connected in series. With the proposed integrated converter, the occurrence of multiple power-point maxima was successfully precluded and the maximum extractable power was significantly augmented, demonstrating the effectiveness and performance of the proposed integrated converter.