Research Of Multiple Frequency Photovoltaic Grid-connected System Based On The Technology Of MPPT

In order to solve the problems caused by conventional energy, new energy, especiallysolar energy development attracted more and more attention because of the irreplaceableadvantages. In recent years, every country competes for the dominance in the solar industry,and has introduced preferential policies to promote the development of solar energy industry,which makes solar power technology become a global issue. The paper focuses onphotovoltaic grid-connected system.Firstly, the structure and output characteristics of the solar cell have been analyzed. Inorder to give full play to the conversion efficiency of solar cells, a maximum power pointtracking method has been raised. The paper has built a solar cell model in the MATLABenvironment, which is equivalent with the actual circuit of the solar cells, and the outputcharacteristic has been simulated. The MPPT(Maximum Power Point Tracking) simulationbased on booster circuit has been done with the perturbation and observation method and theimproved incremental conductance method.Secondly, the types and control strategy of PV grid-connected inverter are studied.Considering the dynamic response and stability of the system,the right inverter has beenchoose.In order to better tracking the phase of the grid voltage, the bias of the grid-connectedcurrent and the instruction current must be eliminated. Improved fixed switching frequencycontrol strategy is used in the inverter control. In order to ease up the contradiction betweenthe switching frequency and switching loss, the multiple frequency SPWM technology is usedto control the inverter.Thirdly, the software filtering method that averaged after removing the extreme is usedto improve the accuracy of the DC sampling. The application of SPLL(software phase-lockedloop) can speed up the system response speed and simplify the hardware circuit. In the end, the correctness of the photovoltaic power generation system has been verified throughbuilding the simulation model of the system, and part of the hardware circuit is designed andthe test results have been given.