Research On Photovoltaic Power Generation MPPT And Grid-connected System

Traditional fossil energy is limited,and people are increasingly aware of the importance of environmental protection.Countries are gradually focusing on the investment and development of new energy photovoltaic power generation.However,the low conversion efficiency of photovoltaics has always been a worldwide problem,so it is extremely important to increase the output power of photovoltaic systems.In order to increase the output power of the photovoltaic cell,the traditional algorithm and intelligent algorithm can be used to keep the photovoltaic cell output at the maximum power.The traditional algorithm is easy to fall into the local optimal value and can not track the global optimal value,and the intelligent algorithm can avoid the problem of falling into the local optimal value through improvement.In this study,the particle swarm optimization algorithm in intelligent algorithm is adopted,and the algorithm is improved to improve the accuracy and rapidity of tracking.Finally,the control method of the inverter of photovoltaic power generation grid-connected system is analyzed,and a harmonic suppression method based on the proportional complex combination of PI control method is proposed,which can realize the rapid tracking of the grid-connected current of the photovoltaic system.It can also suppress the low-order harmonics,and thus can meet the power quality requirements of the power grid.The work carried out is as follows:(1)Analyze various types and structural compositions of photovoltaic power generation systems,and then theoretically analyze the working principle of photovoltaic cells and their common mathematical models,focusing on the effects of local shadows on photovoltaic arrays,by paralleling the ends of photovoltaic cells.Road diodes to solve hot spot problems in photovoltaic systems.(2)Photovoltaic cells are connected in series to simulate a photovoltaic array,and bypass diodes are connected in parallel at both ends thereof to set different illumination intensities to simulate the influence of local shadows on the photovoltaic arrays,and the photovoltaic arrays are represented when occluded.The voltage and power characteristics that come out.(3)Compare and analyze traditional methods and intelligent algorithms for PV maximum power tracking.The traditional maximum power tracking method is easy to fall into the local optimum value for the maximum power tracking of the photovoltaic under the shadow,and the error is large.After comparing a variety of intelligent algorithms,this study selects the particle swarm optimization algorithm,and improves the particle size of thepopulation by optimizing and setting the inertia weight of the linear change.Finally,the Matlab/Simulink simulation system is built to verify that the improved particle swarm optimization algorithm can quickly trace the global The optimal value,and the new global optimal value can be traced when the lighting conditions change.(4)There are a large number of low-order harmonics in the photovoltaic power generation system.The PI controller can track the DC-free static error.The PCI regulation method can compensate the harmonics of specific frequencies to reduce the harmonic content in the power grid.In this study,the combination of PI regulation and proportional complex integration(PCI)regulation was used to reduce the total harmonic content of the grid-connected current from 3.85% to 1.56% of the traditional PI regulation method,and it can eliminate two well.The coupling problem caused by the interaction of the governor increases the robustness of the system and can meet the requirements of the power quality of the power grid.