Study On Design Of Small Power Photovoltaic Grid Connected Power Generation System Based On Variable Step Size Adaptive Control

Solar energy as a clean renewable energy to get the attention of the state and the society,the use of solar power generation has become the trend in the field of energy consumption.For the key problem of solar power generation,the one is the tracking control of the maximum power point.Take up the corresponding control algorithm to make the system output the maximum power quickly and maximize the efficiency of solar energy.The other is to control the grid-connected inverter,and improve the output power quality of photovoltaic grid-connected power generation system.First,this paper discusses the significance of solar power generation and development at home and abroad,a photovoltaic cell engineering model,output characteristics and changes in light and temperature conditions of the photovoltaic cell are analyzed by computer simulation;This paper analyzes the topology of grid-connected inverter system and introduces two main classification methods: isolation classification and power conversion classification.On this basis,the two-stage grid-connected power generation system is used.The pre-stage uses the Boost circuit,and the full-bridge inverter is adopted of the post-stage DC-AC conversion circuit.Secondly,three traditional MPPT control algorithms are commonly studied in depth to analyze their advantages and disadvantages.For example,the traditional methods have the problems of being sensitive to environmental factors,tracking speed lowly and energy fluctuation,etc.In view of this,the variable step adaptive MPPT method is used.In the MATLAB/Simulink environment,the simulation models of photovoltaic system,maximum power point tracking output are established.Simulation results show that this method can quickly track the maximum power point of the photovoltaic array and improve the energy conversion efficiency.At last,analyzed the control mode of photovoltaic grid-connected inverter and the output current control method is chose.Study the control technology of output current on the grid-connected inverter.PI control is usually selected,but the PI control is often unable to control the fast changing cycle quantity.This paper has optimized the PI control and chooses iterative proportional integral.Set up the objective function and derive the expression and transfer function.Similarly,simulation verification is carried out by MATLAB/Simulink simulation tools.The simulation results show that this method can keep the sine wave current output of grid-connected inverter in the same frequency and phase with the power grid,and its output can meet the requirements of grid-connected electricity.