The Research On Three Phase Double Stage Photovoltaic Grid Connected System

Solar energy is becoming more and more important.The photovoltaic cell has strong nonlinear characteristics.The maximum power point tracking of photovoltaic cells is a research direction.Photovoltaic grid connected power generation system is taken as the research object,the specific research contents are as follows:Firstly,discussing the background and research status of the project and introducing the principle and basic components of photovoltaic grid connected power generation system.Secondly,the working principle of photovoltaic cells is studied.The expression of output characteristics of photovoltaic cells in engineering is deduced.The results show that the simplified engineering battery model can reflect the characteristics of photovoltaic cells.Thirdly,the principle of maximum power point tracking is analyzed.The advantages and disadvantages of the commonly used control methods are compared.The principle of BP neural network and genetic algorithm is discussed.The genetic algorithm is used to optimize the BP neural network.The idea of large variation is introduced into the genetic algorithm and the large variation genetic algorithm is proposed to optimize the BP neural network.The maximum power point tracking model of LGA-BP is built and simulated.From the simulation results,it can be seen that improved method can better track the maximum power point of photovoltaic cells.Finally,a three-phase two-stage photovoltaic grid connected power generation system is set up.The control strategy of the inverter is studied and analyzed.The two loop control strategy is selected.The outer loop adopts the voltage control strategy and the inner loop adopts the current control strategy.The topological structure of photovoltaic system selected is two level energy conversion structures.The former is DC-DC transform;the maximum power point tracking is realized.The later stage is DC-AC transformation to achieve the goal of inverting and grid connected.The simulation model of the whole photovoltaic grid connected power generation system is built in Matlab/Simulink.Through the simulation results,it can be seen that the photovoltaic system has reached the requirements of grid connection.