Multi-Mode Operation Control Strategy for Photovoltaic Energy Storage Systems with Shared Current Loop

Abstract

Aiming at the output deficiency of the photovoltaic (PV) system caused by the deviation of the photovoltaic operating point during the environment change, and the DC-link overvoltage resulted from the excess output power, a multi-mode operation control strategy for photovoltaic and energy storage systems is proposed in this paper. Based on the conventional perturbation and observation (P&O) method, the response performance of the PV system under the proposed operation control strategy is improved when the environment changes. In addition, the proposed operation control strategy can stabilize the DC-link voltage through the constant voltage control (CVC) mode, thereby dynamically adjusting the photovoltaic power output and avoiding the battery overcharge. In constant power control mode (CPC), the direct control of photovoltaic output power can be realized. By sharing the common current loop, the system can switch smoothly and run stably among three modes, avoiding the photovoltaic output power oscillation caused by frequent mode switching. Finally, a simulation model of the photovoltaic energy storage system is constructed, and the simulation results are analyzed in detail, which fully validates the feasibility and effectiveness of the proposed multi-mode operation control strategy.