Research On Control Strategy And Grid Connection Of Photovoltaic Power Generation System

Energy is an important material basis for the national economic development and national life.With the increasing demand for energy,the reserves of non renewable energy such as oil,coal and natural gas are increasingly exhausted,so it is particularly important to develop and utilize renewable energy.In this paper,the efficiency and clean solar energy resources are improved by combining MPPT control algorithm,grid connected inverter circuit and its control method.First of all,the main power of photovoltaic power generation system comes from photovoltaic array.Combined with the principle of photovoltaic power generation,the mathematical model of photovoltaic cells is established,and the working conditions of maximum power point of photovoltaic cells at different temperatures and radiation intensities are studied.By analyzing the working principle of MPPT,several common MPPT algorithms are compared and analyzed.Based on the traditional disturbance observation method,a new variable step size adaptive disturbance observation method is proposed,which can quickly track the maximum power point of photovoltaic cells and reduce the oscillation amplitude.In addition,several working states of the DC/DC boost circuit are analyzed,and the parameters of the circuit are calculated and designed,which provides sufficient DC voltage for the inverter circuit.Secondly,the structure of the inverter grid connected circuit is analyzed,the non isolated two-stage photovoltaic grid connected power generation system is selected,and the control strategy of the inverter in the inverter circuit is studied.Finally,the output AC is determined as the control object of the inverter,the double closed-loop control mode of voltage outer loop and current inner loop is adopted,and the control mode of PI and PR is adopted for the current inner loop,According to the simulation results,the advantages and disadvantages of the two methods are compared.Finally,the whole photovoltaic grid connected system is designed by combining boost circuit and inverter circuit,and the simulation model is established by using Matlab/Simulink module.Under the condition of standard condition and radiation intensity change,the simulation results of PI and PR control methods are compared.The results show that the grid connected current and grid voltage meet the basic requirements of grid connected at the same frequency and in the same phase.The THD value of grid connected current under PR control is smaller than that under PI control,and the harmonic distortion rate is lower,which is more conducive to grid connection and stable operation of the system.