Research On Maximum Power Point Tracking And Grid Connecten Control Strategy Of Photovoltaic Systems

Much fossil energy has been used by the whole world not only pollutesenvironment, but the total storage of fossil energy is reducing. The wholeworld is facing the pressure of energy crisis and environmental problems.Solar energy has the advantages of non-polluting and renewable amongother energy and becomes the research focus. In the process of using solarenergy, Photovoltaic maximum power tracking directly affects theutilization of solar energy. Photovoltaic inverter control strategy directlyaffects the grid electricity utilization ratio and the quality of the gridelectricity. Therefore both of them become the key problems to use solarenergy, but each of them still exists some problems. On these issues themajor work of present paper is as follows:Firstly, Choosing the perturbation and observation method which hasthe advantages of simple control, less parameters measured and has beenwidely applied in photovoltaic power generation system, Analyzed itsproblems of misjudgment and oscillation which caused by perturbation stepand great change environment. A new MPPT of photovoltaic method wasproposed which based on the area difference. Depending on the areadifference this method can realize the adaptive regulation disturbance steplengths. Therefore this method can make up the shortage of Theperturbation and observation method which caused by perturbation stepand great change environment. According to the established simulationmodel to study area difference method and perturbation and observationmethods. Simulation results show that new improved method do not existoscillation and can quickly finish maximum power tracking though external changes of the environment, making up the shortage of perturbation andobservation method.Secondly, Established mathematical model of three phase PV inverter.Analyzed PI double closed loop control strategy which has well dynamicand steady performance and has been widely used in grid connected PVsystem, On these issues of control the current loop exists steady-state errorand the system has weak anti jamming performance of grid, this article hasintroduced the proportional resonance control, using the feature of PRcontroller which has infinite amplitude gain in the resonant frequency toeliminate steady-state error of current loop and improved disturbanceresistance of grid, In order to further improve the performance of thePR control, using the improved quasi PR control, Analyzed the advantageof quasi PR controller which compared with PI controller in steady-stateerror and anti-interference ability of grid,Designed the phase compensationof quasi PR controller,Then built the whole grid simulation system,Compared with PI controller and quasi PR controller about simulationresult to prove the superiority of quasi PR control.Finally, Based on the theoretical analysis and Simulation verification,Did the experiment in a3KW experimental platform of PV powergeneration system which uses TMS320F28035as control chip, Designedthe software flow chart and Debugging program, analyzed experimentresults which show the correctness and effectiveness of the design method.