Research On Maximum Power Point Tracking Strategy Of Photovoltaic System Under Partial Shading Conditions

Under the background of controlling global warming by China and other countries,photovoltaic power generation system has become the main body of the new renewable energy system with a high proportion of new energy.For disadvantages of low photoelectric conversion rate and low power generation efficiency due to insufficient illumination,the maximum power point tracking technology is one of the most effective method to optimize the design and operation of photovoltaic system.And MPPT technology based on intelligent optimization algorithm has been widely used in photovoltaic power generation systems under different application scenarios and climate conditions due to its independence,strong generality and the ability of global search.The tracking performance of MPPT technology based on intelligent optimization algorithm is affected by many factors such as the initial population,location distribution and parameters setting.At the same time,the response time of convert system greatly limits the tracking speed.Aiming at the above problems,a dynamic particle maximum power point tracking strategy is proposed in this paper to achieve the maximum power output of photovoltaic array under partial shadow conditions.The main research contents are as follows:(1)The development status and existing problems of MPPT methods are discussed.By establishing a model of photovoltaic cells,the output characteristics of photovoltaic arrays are analyzed,including the number and the distribution of local points in the power-voltage characteristic curve.Based on the above discussion and analysis,the research and design direction of MPPT strategy based on intelligent optimization algorithm is determined.(2)By analyzing the system response of Boost converter,the concept of instantaneous sampling method is introduced to sample the voltage and current before the system is stay steady.Whereafter,the paper proposed a dynamic particle maximum power point tracking strategy.This strategy improves rules of cuckoo search algorithm in initial setting and motion formula of particles.Through depicting the out-put power-voltage characteristic curve of photovoltaic array in global mode and tracking the maximum power point exactly in local mode,the photovoltaic array can work at the maximum power point quickly.(3)The small signal models of Boost converter and Sepic circuit combined with photovoltaic array are established to analyze the dynamic response of DC-DC converter in photovoltaic power generation system.Whereafter,the paper discusses the extensibility of dynamic sampling method in DC-DC converter of photovoltaic power generation system and the failure of P&O method under partial shadow conditions.(4)The simulation model of photovoltaic power system based on Boost converter under complex environment is established in Matlab/Simulink.And the simulation analysis is carried out with the proposed strategy and six maximum power point tracking methods to evaluate the ability to deal with partial shadow conditions and rapidly changing weather.Simulation results show that the proposed strategy is superior to the compared method in tracking efficient,tracking speed and success rate.The experiment platform is built to verify the feasibility of the proposed strategy and the result is consistent with the simulation results.