| Along with the advance of human society and the rapid development of economy, the fossil energy become scarcity and the resulting environmental pollution problem caused by utilization of fossil energy is increasingly prominent, it has become the fundamental way to solve the energy problem for new clean, renewable energy. Photovoltaic (PV) power generation has became the most massive prospects for the development and utilization of new energy use by far with its advantages of larger reserves, clean environmental protection. Due to the influence of irradiation intensity, environmental temperature and external load, the output power of photovoltaic battery varies seriously. Although the technology of photovoltaic is mature, low efficiency and high cost is also the key problem. In order to improve the efficiency for the use of solar energy of photovoltaic battery, photovoltaic cells should be able to adapt to the changes of the external conditions in time and work in the maximum power points. So studying the method of maximum power tracking (MPPT) has important practical significance.Based on the mathematical model of the photovoltaic power generation system, the output characteristic of photovoltaic battery, the working principle of Buck voltage converting circuit, dynamic behavior characteristics of photovoltaic power generation systems, the role of important parameters in photovoltaic power generation system and maximum power tracking control strategy were studied in detail.First of all, beginning with the physical foundation of photovoltaic power generation (photovoltaic effect), through the analysis of the equivalent circuit of photovoltaic cells, the simulation mode of photovoltaic cell was established based on MATLAB/SIMULINK simulation platform; on the basis of the research above, the output characteristics of photovoltaic cell has made; omitting the equivalent series resistance of photovoltaic cell in the study of photovoltaic power generation system, it is convenient to analysis and research of the maximum power control strategy.Secondly, the comparison of several common DC/DC conversion circuit topology structure has made and the analysis of the characteristics of the independent photovoltaic power generation system has performed. Building the simulation model of photovoltaic array and Buck converter based on the theoretical analysis and the simulation of maximum power point tracking for photovoltaic power generation is constructed and the dynamic behavior characteristic are also analyzed; at the same time, several important parameters is analyzed.Finally, for photovoltaic system it is the core problem to find the optimal working point and develop the conversion efficiency of photovoltaic cells. In a wide range of maximum power point tracking control method of photovoltaic power generation, the most widely used strategy are disturbance and observation(P&O) method and incremental conductance(IncCond) method. This article describes the principle of disturbance observation method, disturbance observation method based on power prediction and fuzzy control; the simulation of several commonly used MPPT techniques has made based on photovoltaic power generation system using MATLAB/SIMULINK simulation software and an improved MPPT algorithm----fuzzy-PID algorithm, has designed.Simulation results show that the algorithm of fuzzy-PID control algorithm is better, for it can transfer quickly and track the maximum power point of PV array accurately under the condition of the external environment varying suddenly, and can significantly reduce the oscillation around the maximum power point of PV array and can reduce the energy loss caused by the oscillation of the operating point about the maximum power point, thus enhancing the PV system efficiency. From the above description, the latter method is better than ordinary MPPT method. |
