MPPT Algorithm Research Of Photovoltaic Array About Using Second-order Differentiation Under Partial Shadow Conditions

Renewable energy is now the focus of research in various countries,and solar energy is one of them.All countries are developing solar power technology,and my country is also vigorously developing related projects.This article mainly studies the problem of maximum output power tracking in multi-peak conditions under shading conditions,and makes specific research on the following points.(1)Through the mathematical model of photovoltaic cells,build photovoltaic cell modules in the Matlab/Simulink environment.Analyze the output characteristic curve under the single-peak condition,and study the mathematical model under the multi-peak condition.The P-U with multiple peaks and I-U with multiple knees are obtained by simulation.According to the analysis of the shielding situation of different series and parallel structures,under different shielding situations,the change law of P-U and I-U curves is obtained,and the optimal design of photovoltaic arrays under shadow conditions is proposed.(2)Research the multi-peak MPPT algorithm under partial shadow conditions,derive the d~2P/d U~2 formula through the output current-voltage relationship of the photovoltaic cell,and analyze the relationship between d~2P/d U~2 and the output voltage U.Then build a model simulation in the Matlab/Simulink environment to get the output characteristic curve of d~2P/d U~2-U under the single peak condition.Analyzing the characteristics of the curve,the second-order differential d~2P/d U~2 can be divided into three areas by taking a threshold value for the single-peak P-U curve,namely,the left side away from the peak and the three areas near the peak and the right side of the peak.After analyzing the output characteristic curve of d~2P/d U~2-U under the multi-peak condition,consider a composite MPPT algorithm,which combines the global voltage sweep method and the P&O algorithm.At the beginning of the algorithm,the output voltage is set to 0,and then an increase step is given.Sweep to the right of the peak,and judge the position of the work in the power-voltage(PU)multi-peak curve by calculating the value of the d~2P/d U~2 variable.When the value of this variable is greater than the threshold,it can be judged that the work is on the left far away from the peak.Use large steps.When it is judged that it is close to the peak,the small-step P&O algorithm is used to find the first peak position,record the corresponding data,and then continue to scan to the right until the scan is completed,and then directly output the position of the global maximum power point in the scan.Finally,the advantages and disadvantages of the composite MPPT algorithm are verified through simulation and comparison,and it is found that the composite MPPT algorithm can find the global maximum power point,with high accuracy and faster speed,and can find a new maximum power again in the case of sudden light changes.