Research On The Maximum Power Point Tracking Algorithm Of Photovoltaic Power Generation System Under Complex Illumination

Photovoltaic cells show different output characteristics with changes in light intensity and temperature.The MPPT controller can control and adjust the voltage or current to make the system output at the maximum power all the time,so as to improve the power generation efficiency of the photovoltaic system.Under the condition of uniform illumination,the power output of PV array presents a single peak characteristic,traditional maximum power point tracking MPPT algorithm such as constant voltage method,perturbation observation method and conductance increment method,has a good tracking effect under this condition.If the lighting is uneven or have the shade.Bypass diode in shade part of photovoltaic modules may conduct and make the output characteristic peak phenomenon.At this time the traditional MPPT algorithm may not be able to trace to the global maximum power point due to the limitations of its own principle and make the PV system output power loss increase.Therefore seeking an algorithm with global search ability is very necessary.In order to improve the efficiency of photovoltaic power generation,the output characteristics and the maximum power point tracking algorithm of photovoltaic array under complex lighting conditions are studied respectively in this paper.The main contents are as follows:Firstly,establish the photovoltaic array model under uniform illumination and local shading.By analyzing the power generation principle of photovoltaic cells,the exponential model of photovoltaic cells is established.However,considering the complexity and applicability of the model,simplify the model and obtain the common working condition model in engineering practice.Then,the mathematical model of photovoltaic array under uniform illumination is deduced based on the working mode model of photovoltaic cell.Focusing on the effect of hot spot effect on photovoltaic array under local shadow,the photovoltaic array model under local shadow is deduced by taking the series-parallel connection of two components as an example.Secondly,simulate the output characteristics of PV array under uniform illumination and local shading.Under uniform illumination conditions,according to the array model built above,the output U-I characteristics and P-U characteristics under different temperatures and illumination conditions are simulated and analyzed in Matlab/Simulink,and compared with the data provided by the manufacturer.Under the condition of partial shade,focuses on the effect of partial shadow of photovoltaic array.A 5 * 5 PV arrays are built in Matlab/Simulink.The influence of photovoltaic array by the way of shadow is simulated and analyzed,and lay a theoretical foundation for local shadow of photovoltaic array peak MPPT tracking study.Thirdly,research on the conventional MPPT algorithm used in uniform illumination,and an improved algorithm is proposed.Considering the disadvantages on tracking speed and steady state accuracy of contradictory in disturbance observation method,an improved algorithm--variable step length disturbance observation is proposed and reduce the influence of the selection of step disturbance on system performance.Through the simulation analysis and compared with conventional disturbance observation method,the results show that the algorithm can efficiently and steadily track the maximum power point of PV array.Fourthly,particle swarm intelligence(PSO)algorithm is studied to track the maximum power point under local shading.Aimed at particle swarm optimization(PSO)algorithm in dealing with nonlinear optimization problem with a fast convergence rate,less adjustable parameters and simple rules and easy to implement,apply the algorithm to partial shadow photovoltaic more peak power point tracking.And in view of the existing basic PSO particle setting experience of initial position and speed,number setting randomly,easily falling into local optimum,appearing premature convergence phenomenon is improved.Establish the simulation model of the MPPT algorithm based on improved PSO by designing a 5*5 PV arrays.The array of the shadow of two different methods are simulated,and compared with the standard particle swarm optimization(PSO)algorithm.The results verify the advantages of the proposed algorithm in search of speed,tracking accuracy and system oscillation.