Research And Implementation Of Integrated Controller For Independent Photovoltaic Power Generation System

The independent photovoltaic power generation system solves the problem of power supply in the areas not covered by the public power grid,which not only relieves the dependence on non-renewable energy,but also helps to protect the environment.Therefore,the research of independent photovoltaic power generation system has become one of the hot spots in the field of photovoltaic application.This thesis focuses on the key technology of integrated controller for power generation and energy storage in the independent photovoltaic power generation system.The main research work is as follows:1.Establish an independent photovoltaic power generation system model.Based on the working principle of photovoltaic cells,the equivalent circuit,engineering mathematical model and simulation model of photovoltaic cells are established,and the I-U and P-U characteristic curves of solar cells under standard and changing environmental conditions are simulated and analyzed.The topological mathematical model of integrated controller’s main circuit based on synchronous BUCK circuit and the equivalent circuit model of lithium battery are established,and the simulation analysis of its output characteristics is carried out respectively,which lays a theoretical foundation for the research of integrated controller of independent photovoltaic power generation system.2.Algorithm research on MPPT(Maximum Power Point Tracking,MPPT)of independent photovoltaic Power generation system.Charging controller based on the traditional independent photovoltaic power generation system of MPPT algorithm principle and advantages and disadvantages of analysis,disturbance observation method for non-uniform illumination changes exist in the process of tracking power point misjudgment and perturbation step size setting cannot take into account the dynamic MPPT steady-state performance problems,based on the traditional MPPT power prediction and adaptive variable step is proposed an improved MPPT algorithm,the algorithm by introducing illumination change rate,the non-uniform change of illumination linearization processing,when changes in the illumination disturbance observation method to solve the nonlinear problems of the power variation of d P misjudgment;According to the characteristics of d P/d U at the maximum power point,a method of normalizing the inverse tangent function to deal with the step size factor was proposed,which realized the automatic adaptation and dynamic adjustment of the step size factor in the MPPT process,and considered the dynamic performance and steady-state performance requirements of MPPT.3.Research on lithium battery charging algorithm of independent photovoltaic power generation system.Research demonstrates the traditional lithium battery charging methods advantages and disadvantages,and the output characteristic of photovoltaic cell components,the MPPT technology into the traditional lithium battery charging algorithm,an improved independent photovoltaic power generation system of lithium battery charge three phase algorithm,realize the MPPT photovoltaic cell components for lithium battery charging,constant voltage charging,floating charge.4.Design and experimental study of integrated controller for independent photovoltaic power generation system.The experimental platform of integrated controller for independent photovoltaic power generation system based on DSP28335 is built.The performance of the improved MPPT algorithm is tested when the system starts up,the environment changes dramatically,the environment remains unchanged and the load changes.The experimental results show that the improved algorithm avoids the problem of disturbance misjudgment when illumination changes,and the dynamic steady-state performance of MPPT is good.Three-stage charging experiment of lithium battery was carried out.The experimental results show that the improved three-stage charging algorithm not only ensures the charging efficiency and the utilization rate of photovoltaic cells,but also prolonging the service life of lithium batteries.In conclusion,the integrated controller of independent photovoltaic power generation system designed in this dissertation realizes the integrated control of power generation and energy storage,and the proposed MPPT algorithm and charging algorithm have engineering feasibility.