Research On Power Control For Stand-alone Photovoltaic Generating Systems

In green and renewable energy, solar energy with unusual advantages is accepted commonly, and photovoltaic (pv) generating systems of its various applications are paid more attention. With simple structure, convenient maintenance and high reliability, stand-alone pv generating systems find a certain degree application in industry and people's daily life, and have tremendous potential development in the near future. The structure, working mechanism and control strategies of stand-alone pv generating systems are studied to further improve its performance, and realize its optimal and reliable operation in this thesis.Firstly, the domestic and oversea development situation of pv generating systems, the system classification and utilizing forms of stand-alone pv generating systems are summarized in the thesis. The configuration and working principle of stand-alone pv generation systems are introduced, and operating principle of pv array, battery, controller as well as model of pv array are discussed.Secondly, based on analyzing the working states of stand-alone pv generating systems, the power control strategy, which consists of maximum power point tracking control, battery charging and discharging, and load power tracking, are given to make the system to operate in both optimal and reliable conditions. MPPT control principle and several existing MPPT control methods are discussed, and a novel maximum power point tracking control strategy with adaptive setting of current loop set point is present. The simulation results show that, compared with fixed step size method, the proposed algorithm has faster and more accurate response to the given set point.Finally, on the basis of analyzing local solar energy and user needs, the main and assistant circuits of the systems are designed, and the inductance designed by AP method is made. The experimental research on Buck converter is implemented, and some results are gained.