Research On Maximum Power Point Tracking And Grid Control Strategy Of Three-phase Photovoltaic Grid-connected

With the gradual maturity of photovoltaic power generation technology,the national policy promoting,application market continues expanding,photovoltaic power generation technology has gradually become the main form of China's solar energy development.Among them,the photovoltaic grid-connected system with high efficiency,less investment,reliable power supply,the obvious advantages compared with off-grid system,has become a main research direction of photovoltaic power generation.In the whole photovoltaic grid-connected system,the maximum power tracking technology and inverter grid-connected control technology directly affect the inverter output efficiency and power quality.Experts and scholars are paying much attention in this.Therefore,this subject has done major research.Firstly,the background and significance of the photovoltaic power generation technology are clarified,and the technical status of the maximum power tracking and grid control of the inverter is summarized.By comparing the topology of the grid-connected inverter,a two-level structure suitable for maximum power tracking and grid-connected control is selected,and the mathematical model is deduced in details in different coordinates.Secondly,the traditional algorithm and intelligent algorithm of maximum power tracking technology are compared,combined with the traditional variable step perturbation observation method,an improved sliding mode control is proposed and verified by Simulink simulation.And Simulink simulation is used to verify the advantages of the algorithm in tracking speed and tracking accuracy.Then,according to the advantages of current-mode grid-connected control,a double closed-loop control scheme with PI regulator and spatial vector pulse width modulation is designed.The simulation results show that the output current of the inverter can track the grid voltage.The harmonic analysis proves the reliability of the scheme.Finally,the problems in the research process of this subject are summarized,and the development direction of PV grid-connected system is prospected.