Research On Multi-peaks Maximum Power Point Tracking (MPPT) Control Method Of Photovoltaic

Nowadays, facing the problems of energy crisis and environmental pollution, the new energy resources with free pollution and high storage are explored for emergency by most countries in the world. Solar energy became one of the important choices on account of its universality, non- pollution, unlimited storage and economic efficiency. Photovoltaic(PV) power generation is one development tendency of solar energy application, and the utilization of maximum power point tracking(MPPT) technology greatly improves the generation efficiency of PV generation system.Fixed on the open space, the PV arrays are under non-uniform illumination and partial shade due to the influence of environment surrounded(like higher architectures, trees and dark clouds in the sky). The output characteristic of PV arrays will be very complex when under partial shade conditions, especially the power-voltage(P-U) curve exhibiting multiple local maximum power points(MPP), thus, leading to the loss of output power. Therefore, MPPT methods trying to find the global MPP(GMPP) should be designed to fit the output characteristic of the PV arrays under partial shade conditions, named multiple-peak MPPT methods. Multiple-peak MPPT methods can reduce the loss caused by partial shade, but the tracking performance of these technologies differs greatly from each other in accuracy, power oscillation and other applications. Also, there is no uniform standard to evaluate the performance of multi-MPPT methods in complex shade conditions. It is very important to judge the quality of numerous multiple-peak MPPT methods and design more efficient multiple-peak MPPT method for improving the generation efficiency of PV system when PV arrays are under non-uniform shading.In this paper, the basic composition of PV system is introduced, the influence of partial shade on the output characteristics of PV arrays is analyzed and the output characteristics are modeled by Matlab. On the foundation of literatures reading in large quantities, the basic principle of several classic multiple-peak MPPT methods based on algebraic algorithm is introduced and the tracking performance(like MPPT success rate and power oscillation) of these methods in large number of typical partial shade cases are compared. Then, an efficient multiple-peak MPPT method is proposed on account of comparison results, which is called multiple-peak MPPT method combining load line with mountain searching(L&H). Also the viability of the proposed method is verified in MATLAB/Simulink environment.The comprehensive evaluation method of multi-peak MPPT algorithm is put forward to judge the comprehensive performance of L&H. First of all, the comprehensive evaluation model is constructed based on the determination of the index and the weight coefficient. Then, the changing partial shade caused by solar height angle on a particular day is molded to evaluate the performance of multi-peak MPPT algorithm corresponding to different index. Based on the simulation results, the grey relation is used to estimate the multi-peak MPPT methods. Results show that the proposed multi-peak MPPT algorithm has advantages on static performance and can perform well in terms of comprehensive performance.