Application Of Battery And Super Capacitor In Energy-Storing Photovoltaic System

Due to the randomness and volatility of photovoltaic power generation, photovoltaic power generation system requires sufficient capacity of the energy storage equipment to provide high quality electrical power. The cost of energy storage device usually occupies 20% to 25% of the photovoltaic power station, life-span of energy storage device is the shortest in PV system. The key to improve photovoltaic power efficiency and quality is how to solve the storage problem. This paper focuses on the application of hybrid energy storage system which composed of super capacitor and battery in photovoltaic power generation.Firstly, the theory of photovoltaic power generation system is introduced in detail, including the off grid and grid connected photovoltaic power generation system. The maximum power point tracking(MPPT) technique of photovoltaic power generation system is analyzed, and the disturbance observation method(P&O) and the incremental conductance method(INC) are also analyzed.Secondly, the charging and discharging characteristics theory of Valve Regulated Lead Acid Battery(VRLA) and super capacitor is introduced. The battery charging control method and the super capacitor series voltage problems are researched in detail. In a large number of energy storage components, super capacitor and battery are complementary in performance, the hybrid energy storage device combined by super capacitor and battery has good performance and potential. According to the different characteristics of the battery and the super capacitor, the structure of the hybrid energy storage of the battery and the super capacitor is presented. The capacity allocation of battery and super capacitor will be more flexible by using current reversible chopping circuit, battery and super capacitor can give full play to their advantages.And then, according to the structure of the hybrid energy storage system, the storage of photovoltaic power generation system energy management control strategy is designed. The flow of energy is controlled by changing the PWM signal of unidirectional converter and bi-directional converter under the different operating modes.Finally, the battery and super capacitor hybrid energy storage system for photovoltaic power generation system model is built on MATLAB. The fluctuation of photovoltaic power generation is simulated by changing the illumination and vacancy load. It is verified that hybrid energy storage structure can weaken power fluctuation.