Photovoltaic Power Generation System MPPT And Island Detection Technology Research

With the increasing energy demand of the current society,the development and utilization of solar energy is an important means to alleviate the crisis of traditional fossil energy.Photovoltaic power generation is the most common application of solar energy,so the study of photovoltaic power generation is of great significance.In this paper,photovoltaic power generation system is analyzed,and photovoltaic cell modeling,maximum power point tracking(MPPT),grid-connected photovoltaic system island effect detection and other aspects are studied.The main contents include:(1)The power generation principle of photovoltaic cells is analyzed,and the current equation of photovoltaic cells is written,the equivalent circuit model of photovoltaic cells is given,and the simulation model of photovoltaic cells is established in Matlab/Simulink to simulate the P-U and U-I output characteristic curves of photovoltaic cells and photovoltaic arrays.The accuracy of the established model is proved through literature comparison.The photovoltaic power generation system,grid-connected inverter and phase-locked loop technology are introduced.The grid-connected inverter and phase-locked loop are verified in Simulink.(2)The conventional photovoltaic MPPT method is introduced and verified by simulation.In view of the problems of oscillation and slow tracking efficiency in the working process of the conventional perturbation observation method,an improved perturbation observation method is proposed,namely: The adaptive differential perturbation observation method introduces the derivative and control factor combination between power and voltage to replace the original fixed step size and accelerate the tracking efficiency.In addition,the application of intelligent algorithm in PV MPPT is introduced,and the tracking effect of particle swarm optimization algorithm(PSO),cuckoo algorithm(CS),Grey Wolf algorithm(GWO)and other common algorithms in PV MPPT is simulated.(3)For the global maximum power tracking(GMPPT)of photovoltaic arrays under local shadows,the conventional MPPT method is easy to fail,the intelligent method is precocious,poor stability and other problems,an improved honey badger optimization algorithm is proposed as the tracking strategy.Firstly,the optimization algorithm of honey badger is introduced,and an improved method is proposed: Tent mapping is introduced to make the population distribution uniform in the initial stage of the algorithm,and speed up the optimization.Finally,the maximum power tracking effect and grid-connected effect of the improved Honey badger optimization calculation under local shadow are simulated.The simulation results show that the improved honey badger optimization tracking effect is good,and it is suitable for grid-connected photovoltaic system.(4)This paper introduces the islanding effect of grid-connected photovoltaic power generation system,and gives examples of conventional detection methods of islanding effect,and analyzes the principle,advantages and disadvantages of conventional detection methods.An improved active frequency offset detection method is proposed in view of the disadvantages of the conventional method: the detection speed is slow and the detection range is small when the positive feedback active frequency shift is used.That is,the sign function is introduced to determine the nature of the load,the detection range is increased,and five times of the maximum value of five perturbations is selected as the offset to speed up the frequency offset,so as to improve the detection efficiency.Finally,the accuracy of the improved method is verified by simulation.