Research On Maximum Power Tracking And Grid-connected Inverter Control Of Photovoltaic Power Generation System

Photovoltaic grid-connected power generation is a relatively mature way to utilizing solar energy at present.In order to improve energy conversion efficiency and realize stable and efficient grid connection in the process of system operation,It is necessary to study the maximum power tracking of photovoltaic cells and the control of grid-connected inverters.In this paper,the maximum power point tracking algorithm and the control strategy of grid-connected inverters are optimized and improved.The specific research work is as follows:(1)Based on the physical characteristics and engineering mathematical model of photovoltaic cells,The output characteristics of photovoltaic cells under uniform illumination and local shadows were analyzed.The simulation results show that the output characteristics of photovoltaic cells vary with the illumination intensity and temperature.At the same time,the multi-peak characteristics of P-V output curve of photovoltaic arrays under local shadows are verified.(2)In order to improve the tracking speed and accuracy of MPPT algorithm,and improve the problem of it is easy to produce oscillation at themaximum power point and fall into local optimum under multi-peak conditions.An improved MPPT algorithm Lévy-FOA is proposed.Introducing the adaptive Lévy flight step into Fruit Fly Algorithm can expand the search range of the algorithm when searching for the maximum power point,restrain prematurity and improve the convergence speed of the algorithm.The simulation results under different conditions show that compared with other commonly used algorithms,the improved MPPT algorithm Lévy-FOA improves the tracking speed and accuracy to a certain extent.(3)Aiming at the problems of complex parameter design,slow dynamic response and high harmonic distortion of current control strategy for grid-connected inverters,a solution is presented.An improved multi-step model prediction algorithm is used to control the output current of the inverter.The reference value of current inner loop is provided by power feed-forward module and MPPT module.The control strategy has low modeling requirements,does not depend on parameter design,does not need PWMmodulation module to generate driving signals,and reduces the delay.The simulation results verify the feasibility of the scheme.It shows that the scheme can improve the response speed of the system,reduce the harmonic distortion rate,and improve the grid-connected ability of the system to a certain extent.