| In the modern society,power supply is having an increasing impact on people’s daily life. Emergency Power Supply(EPS) can continuously provide power to the load when the utility grid is powered off, and it can guarantee the user’s demand for power, so it is used more and more widely. With the development of the solar power generation technology, applying the solar power generation technology to the battery energy storage system gradually becomes an important trend for the development of EPS.The paper has researched on Emergency Power Supply system of photovoltaic energy storage. The system is composed of photovoltaic charging system, conventional charging system and inverter.By using photovoltaic charging system and conventional charging system, the battery is charged completely. The diversity charging mode has improved the reliability and power quality of Emergency Power Supply,prolonging the time of power supply.The paper firstly introduced the overall design scheme of photovoltaic energy storage EPS system,described the composition and working principle of Emergency Power Supply system,and illuminated the working process of EPS under different conditions in detail, then introduced the technical index and the design requirements of each part.Next, the paper analyzed the inverter system of Emergency Power Supply in details. According to the technical index, boost-inverter circuit is selected as the main circuit topology, then the topology of the inverter and the boost circuit is determined.The selection of power switch, capacitance and inductance were analyzed in details, the formulas was presented.The design of the drive circuit for power circuit is described. Meanwhile, the SPWM control principle of the inverter circuit is introduced, and the formation process of SPWM wave is explained. To ensure the stability of the inverter output, the voltage negative feedback closed-loop control systemis designed.The flow chart of the software design of EPS is given.Thirdly, the paper introduced the charging circuit of batteries. The battery charging characteristics is described. Through the comparison of various charging method, the “constant voltage-constant current-floating” three step charging method is selected. The charging circuit is designed. The voltage and current sampling circuit of the battery is designed. Then the charging circuit and sampling circuit composedthe three stage charging system.Through the charging experiment of the batteries, the feasibility of charging method is verified.Fourthly, the principle of photovoltaic cell is amply described. The model of photovoltaic cell and detailed formula is given. According to the mathematical model, the output characteristic of photovoltaic cell is determined. Through the comparison of several common MPPT control methods, the perturbation and observation method is selected. The charging circuit and control diagram for battery charging by photovoltaic cell are given. Through establishment of the model and simulation in Matlab/Simulink, the validity of photovoltaic storage charging method is verified.Finally, the EPS prototype is established. The inverter circuit and the charging circuit were combined debugged.Through the observation of the drive and output waveform, Proofed that the EPS prototype achieved the designed technical specifications, and realized the expected function. |
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