PWM- and PFM-controlled switched capacitor converter-based multiport converter integrating voltage equalizer for photovoltaic systems

Photovoltaic (PV) systems consist of multiple dc-dc converters, including a front-end converter for PV string control, a bidirectional converter for battery regulation, and voltage equalizer to preclude partial-shading issues, and hence they are prone to be complex and costly. To cope with this issue, this paper proposes the PWM- and PFM-controlled switched capacitor converter (SCC)-based multiport converter (MPC) integrating voltage equalizer. The proposed MPC can be derived by integrating a bidirectional PWM converter, series-resonant converter (SRC), and SCC. The PWM converter and SRC regulate battery and load voltages, respectively, while the SCC plays a role of the voltage equalization. Not only is the system as a whole dramatically simplified but also the circuit element count is significantly reduced thanks to the integration. The 150-W prototype for three PV modules was built for verification. The experimental results demonstrated the extractable maximum power from PV modules was significantly improved by the SCC, while the battery and load voltages were individually regulated by the PWM and PFM controls, respectively.