Research On Photovoltaic MPPT And Grid Connection Control Strategy Based On Partial Shading

With the continuous consumption of global energy,new energy is increasingly valued,and among many new energy sources,sustainable energy,mainly solar energy,is highly favored.In recent years,the installed capacity of photovoltaic power generation equipment has been increasing year by year,so studying photovoltaic power generation has important practical significance.When a photovoltaic cell is partially occluded,it will affect its output characteristics and reduce the photoelectric conversion efficiency.Therefore,it is necessary to choose appropriate methods to find and track the maximum power point.This article takes advantage of the advantages of the Grey Wolf algorithm and the incremental conductance method,and proposes an improved method that combines the Grey Wolf algorithm and the small step incremental conductance method.In response to the lack of search speed in the Grey Wolf algorithm,the next search of the Grey Wolf algorithm is improved by using dynamic weights.The process of searching for the maximum power point is divided into two stages.Firstly,an improved Grey Wolf algorithm is used for global search,and then a small step conductance increment method is used for local search.The simulation results show that under static occlusion,the proposed method takes less time to search for the maximum power point compared to the Grey Wolf algorithm;Under dynamic occlusion conditions,the response time to rediscover the maximum power point reaches 0.25 seconds.The AC signal in the static coordinate system will be converted into a DC signal in the rotating coordinate system,which will reduce the control difficulty of the inverter.This article discusses a control strategy in a rotating coordinate system.Firstly,the AC side current value of the inverter is collected,and an orthogonal signal is established using double second-order generalized integration,followed by a certain degree of filtering;Secondly,by using coordinate transformation to convert the AC signal on the inverter’s AC side into a DC signal,fuzzy PI control is applied to each of the two DC signals;Finally,in order to solve the problem of grid disturbance during grid connection,grid voltage feedforward control is applied to the DC quantity in the rotating coordinate system to achieve high-precision tracking of grid connected current.In order to solve the phase and frequency errors of grid connection and improve system stability,a double second-order generalized integral phase-locked loop is adopted.Finally,through simulation verification,the experimental verification shows that the THD content of the proposed control strategy is only 0.37% in 0.8s,which is significantly improved compared to fuzzy PI.