The Fuzzy PID Control Of The MPPT For The Stand-alone Photovoltaic Generation System

Energy is the mother of varieties of industry. As the survival fossil energy is declining day by day, It's imperative to develop green and renewable energy. In all kinds of these new environment-friendly energies, the solar energy with its unmatchable advantages of non-pollution and abundant reserves has attracted more and more attention, and the most promising prospect of its applications is the photovoltaic energy. However, the problem as the high initial investment costs and the low conversion efficiency in the process of development and utilization of the solar energy is still exist. Maximum power point tracking (MPPT) technology can maximize the use of solar energy, so it can improve the conversion efficiency and increase investment utilization ratio and its recovery. In presenting the MPPT technology as the research goal, the thesis focuses on the stand-alone photovoltaic power generation systems, which includes the simulation and the theory of the maximum power point tracking(MPPT) technology.Firstly, this thesis analyses the composing of the stand-alone photovoltaic generation system, make a detailed analysis of the photovoltaic cells for the core modules in the system including the circuit model and the electrical characteristics. On these basis, this thesis build simulation model of photovoltaic cells under Matlab/Simulink, it can pvovide the theoretical basis for the maximum power point tracking (MPPT) research and simulation in the subsequent chaters.Secondly, adopt the method of changing the duty ratio of the DC/DC circuit to achieve the MPPT of the photovoltaic generation system.The circuit includs major loop and control loop, in the light of the features and requirment of the photovoltaic power generation systems, choose the boost circuit as the major loop by comparing the characteristics of the buck and boost circuit, and design the boost circuit and the control loop in which the Atmega-8 is the master chip including the drive circuit, electric signal acquisition circuit and conditioning circuit. The main software design flow chart is also given in the thesis.Lastly, Research and analysis of the maximum power point tracking (MPPT) methods is indispensable, as it is an important mean to achieve the maximum power point tracking (MPPT). Based on the simple analysis of the existing common algorithm, for the defects of these common algorithm, The fuzzy PID algorithm is proposed in the thesis. Furthermore build the simulation model under the Matlab/Simulink for this algorithm based on the boost circuit. The simulation results show that when the external environment is stable, the photovoltaic system can run in maximum power point(MPP) with static performances, when the temperature or the sun light intensity changed suddenly, this method can track the external environment changes quickly, and the system can output conversion energy steadily and efficiently with good dynamic and static performances. It has the important theoretical and practical significance in the photovoltaic generation system.