A Shared Loop and Mode Normalized Control Method for Standalone Photovoltaic Energy Storage Systems

With the rapid growth in demand for photovoltaic (PV) power generation, standalone photovoltaic energy storage systems (SPESS) are gaining popularity. However, existing SPESS control methods commonly face issues such as mode-switching impact and low light-load efficiency. To address these challenges, this paper introduces a Shared Loop (SL) and mode normalized control method for complex SPESS. Diverging from traditional control approaches, the proposed method enables adaptive adjustment of the photovoltaic system's output power based on the load state without the need for mode switching. Consequently, it enhances the system's dynamic performance while completely avoiding voltage and current shocks associated with mode switching. The incorporation of a shared loop empowers both the PV system and the energy storage system to regulate the DC voltage. The ESS plays the role of the main bus voltage controller, and the PV system assists the regulation of the bus voltage. Moreover, the ESS can dynamically adjust charge and discharge currents based on the battery pack's charge state, ensuring balanced energy distribution among the batteries. To validate the efficacy of the proposed control method, a simulation model of an isolated SPESS is constructed. Simulation results demonstrate that the proposed control method minimizes system energy loss and enhances overall energy utilization efficiency.