PWM switched capacitor converter integrating voltage equalizers for series-connected energy storage cells and photovoltaic modules

In recent photovoltaic (PV) systems, an energy storage source is often installed for power leveling and/or night-time power supply. However, such PV systems require multiple converters, including a voltage equalizer for series-connected PV modules to preclude negative impacts of partial shading, central converter for PV string control, and equalizer for series-connected energy storage cells to ensure years of safe operation, and therefore, PV systems are prone to complexity. To realize the system-level simplification, a PWM converter integrating voltage equalizers for PV modules and energy storage cells is proposed in this paper. The proposed integrated converter comprises a switched capacitor converter (SCC), PWM buck converter, and series-resonant voltage multiplier (SRVM) that perform PV equalization, string control, and cell equalization, respectively. The derivation procedure of the integrated converter is explained and discussed, followed by operation analysis. An experimental test was performed using series-connected supercapacitor (SC) modules and solar array simulators to emulate a partial-shading condition. With the integrated converter, the extractable maximum power from the PV modules was significantly improved while voltage imbalance of SC modules was adequately eliminated, demonstrating the integrated performance of the proposed converter.