The Research Of Maximum Power Point Tracking Technology In Photovoltaic Grid-connected System

Solar power is a new green power. It is regarded as clean, pollution-free, and inexhaustible. Photovoltaic conversion is an effective way to use solar power. Because the price of photovoltaic cell is expensive and conversion efficiency is low presently, the Maximum Power Point Tracking is absolutely necessary, in order to decrease system cost and increase efficiency.As a core component of photovoltaic power generation systems, the size of the photovoltaic cell's output power is a very important technical indicator. But affected by external conditions, the output power of photovoltaic cells has not always kept at the largest state, so when it should produce changes in real-time accurate tracking. The factors that affect the maximum power point are mainly light intensity and temperature. When external factors change, the maximum power real-time tracking techniques must be used in photovoltaic power generation system, it makes the photovoltaic cell array can be the greatest power output.The paper focuses on the photovoltaic grid-connected system and analyzes it with theory. We pay the emphases on the implementation about selecting parameters, topology structure, control strategy, MPPT, and so on. The main contents are listed as follows:Firstly, the background of the study and the situation of photovoltaic system were introduced.Then, the mathematical model and simulation of Photovoltaic cells was established, and specific MPPT algorithms were researched. The mathematical model of PV cells was established. Trough MATLAB simulation, non-linear of Photovoltaic cells was verified. With compare of several maximum power point tracking(MPPT) methods, an improved P&O was adopted and the duty cycle was changed to achieve MPPT purposes.Thirdly, main circuit and control systems were selected and designed. By Boost circuit, DC-DC conversion circuit used in MPPT was designed. Sampling circuits of the photovoltaic cells output current and voltage and drive circuits are realized. MPPT control system was designed on the base of MSP-TS430PM64A99.Finally, the models and MATLAB simulations of P&O, INC and improved P&O were established. The simulation results show that the improved P&O method is feasible, algorithm started quickly, tracked accurately.