The Study On MPPT Control Algorithm Of Off-grid Photovoltaic Power Generation System

With the progress of human technology,environmental pollution becomes more and more serious.so finding green and pollution-free new energy sources to replace traditional energy sources become more and more important.As a new type of energy with large reserves,no pollution and no noise,solar energy has become the hottest applied research field in new energy.The use of the solar energy is that photovoltaic systems.The two factors that affect the efficiency of pv system are external temperature and light intensity.The influence of light intensity has the complex partial shade,which can cause the power instability of the photovoltaic system.The traditional maximum power point tracking algorithm is easy to get into local maximum power point optimization under partial shade.Therefore,the study of the new maximum power point algorithm in photovoltaic system is a shortcut to improve the power generation efficiency of photovoltaic power generation system.In order to improve the poor tracking precision,slow speed,easy oscillation in the traditional maximum power point tracking(MPPT)algorithm of PV(photovoltaic)cells,an algorithm based on cuckoo search algorithm(CSA)and The improved variable step size perturbation and observation(P&O)method was proposed.First CSA was used to quickly locate approximate maximum power point(MPP)when the PV cells system started or the temperate,light mutation occurred,then the variable step size perturbation and observation(P&O)method based on the Fibonacci sequence could find precise MPP based on the approximate MPP that the CSA found.A simulation model was designed in the Matlab/Simulink,the simulation results show that this MPPT algorithm has the ability to track the MPP of photovoltaic cells quickly and accurately.At the same time,the conditions of the termination and the restart of the whole algorithm are set up in the algorithm of each phase.The power change of the pv array was different due to the different algorithms in the absence of shadows and the partial shadow of the photovoltaic array.Therefore,the simulation model was established in Matlab/Simulink environment.Simulation of two situations,no shading situation,partial shadow shading situation;And the characteristic curves of different MPPT algorithms were drawn respectively.The proposed algorithm was compared with the traditional maximum power point tracking algorithm and proved the advantages of the new algorithm in precision and speed.In order to test the performance of the algorithm in the real system,the MPPT experiment platform was designed.With TMS320F2812 as the core of the main control circuit,CCS3.3 was adopted to program the main program and sample program.Compared with the traditional algorithm,it proves that the algorithm has certain advantages in the maximum power tracking in practical applications.Both the simulation results and the experimental results show that the cuckoo search algorithm with the improved step-size perturbation and observation have performed well in partial shadow occlusion and no shadow occlusion.The experimental results show that the hybrid algorithm is not only good in dynamic performance,fast tracking speed,but also stable and efficient to increase the efficiency of the pv array.It is practical impetus to the development of the maximum power point tracking technology.