Study On Control Method Of Maximum Power Point Tracking Of PV System Under Hot Spot Effect

Solar energy has been regarded as one of the new energy sources in the future,and been generally concerned by people.However,in the practical engineering applications,there are still a lot of problems that need to been solved urgently in the photovoltaic electric generation field.And,one of the key technology is to solve the hot spot effect caused by complex partial shading condition.The hot spot effect not only reduces the output power of the photovoltaic(PV)system,but also damage the cells’ life in the untreated controls in long time.Therefore,it is very necessary to study on the intelligent control methods with hot spot effect for the efficient output of PV power generation system.Through reviewing the related literatures and technical data at home and abroad,this paper introduces the mathematic model and engineering model,and analysis on the output characteristics of solar cells under different environmental conditions by the simulation,and introduces the generation mechanism of hot spot effect.When the PV arrays under the shading conditions,the photo current of the PV cells decrease,and flows through the parallel resistance increase,the consumption of power increased.With the passage of time,the PV array will produce the hot spot.In order to deal with the multi-peak characteristics of the P-V curve under partial shading condition,this paper proposes a novel maximum power point tracking(MPPT)control method based on an improved particle swarm optimization(PSO)algorithm and variable step perturb and observe(P&O)method.This method can improve the quality of initialization particles,referring to the characteristics of PV system.The grouping idea is introduced into the PSO algorithm,the superiority of the improved algorithm over the traditional PSO algorithm in terms of tracking speed and less power oscillation is highlighted for the multidimensional nonlinear functions.And in order to reduce computational complexity of algorithm near the maximum power point(MPP),the variable step P&O method is used to instead of PSO algorithm,and track the global maximum power point accurately with the change of environment.This paper took use of MATLAB/SIMULINK to build the equivalent circuit model for PV cell with package,and build the stand-alone photovoltaic power system modeling composed by Buck-Boost converter.Compared with the different MPPT algorithms through simulation experiment,the results show that the proposed method can effectively track the global maximum power point of PV system under partial shading condition with more quickly and smaller oscillation.Finally,this paper also made the hardware test of MPPT in outdoor environment,and the experimental data show this method has feasibility.