Research On Global Maximum Power Point Tracking Algorithm Based On Topology Of PV Array

With the development of technologies, the traditional energy sources have been unable to meet the needs of rapid economic development. Solar as a green energy, has become the consensus of mankind. At the same time, photovoltaic technology, as the primary method of solar energy using, has been a focus in the study of many scholars in recent years. At present, the photovoltaic technology of the maximum power tracking has been a mature one and gets a wide range of application. But the output curve of PV array under the influence of shading illumination condition shows a multimodal phenomenon, and the conventional MPPT technology will fall into the local peak point and affect the output efficiency. It is great significance to study the global maximum power tracking control method of PV array under the shading illumination, to improve the efficiency of photovoltaic power generation.The paper puts forward a global maximum power tracking control strategy of series photovoltaic arrays under the complicated illumination conditions, and the feasibility of the strategy is verified in the Matlab/Simulink platform and the experimental platform.Firstly, based on established simplified equivalent mathematical model of the equivalent circuit of the photovoltaic cell, the correction coefficient is introduced according to the influence of illumination and temperature change of the PV array,in order to get the engineering accuracy simulation model to meet requirements of any environmental conditions. By using the simulation model, the output characteristics of photovoltaic cells under different illumination intensity and temperature are analyzed.Secondly, combined with the non-linear characteristics of photovoltaic cells, the principle of using of the Boost circuit to reasize maximum power tracking is analyzed. The Perturbation and observation method is emphasized by the paper. Comparing the difference between the duty cycle disturbance and voltage disturbance, the disturbance step size and disturbance frequency are determined. The performance of Perturbation and observation method is analysis under the condition of uniform illumination, illumination mutation and illumination continuous change.Thirdly, the hot spot effect, and multi peak of photovoltaic array are analyzed and researched. The current photovoltaic array topology is introduced, and the PV array output efficiency with different topology under different shading conditions is evaluated. The string PV arrays are selected as the base for the global maximum power tracking control strategy. Combined with a single photovoltaic cell mathematical model, the string PV array model is derived. Based on the perturbation method of observation, global photovoltaic array maximum power point tracking control strategy is conducted and verified by simulation under the conditions of uniform, shading and changing illumination.Finally, a small-scale photovoltaic power generation system test platform is constructed, and the hardware structure, parameter determination, component selection, circuit design and debug controller are introduced. According to the problems to be validated, the experiment schemes in four different conditions are designed, and the experiment results indicate that the proposed control strategy can effectively track the global maximum power point of PV array, to improve the efficiency of array output.