New Five-Level PV and Energy Storage Converter with Independent MPPT Control

In order to achieve efficient integration of photovoltaic and energy storage, a new five-level photovoltaic (PV) and energy storage converter with independent maximum power point tracking control (MPPT) strategy is proposed. Firstly, the topology and working principle of the five-level PV-storage converter are researched, and the charging and discharging states of the capacitors with different working state are presented. Then a control strategy for mid-point unbalance compensation of the DC side capacitor and the charging and discharging control of the energy storage battery are presented which could realize the DC capacitor balancing or unbalancing. By independently adjusting the DC voltage of the upper and lower groups on the DC side of the five-level converter, the independent MPPT of two sets of photovoltaic cells in series can be realized. When the lighting of the two PV cells in series is different, it can still ensure that the respective PV cell work at the maximum power point. This principle can effectively improve the power generation of the photovoltaic system. The effectiveness of the proposed method is verified by the experiments on the hardware platform.