Research And Design Of Photovoltaic Charging Controller Based On MPPT

With the advance of human culture and the development of economy, the energy crisis and environmental problems increasingly draw attention from people. As the representative of clear new energy, solar energy becomes one of the forms of energy with great development on a global scale. One of the applications of solar energy is PV system, in which the output effect of photovoltaic cells and the working function of energy storage determine the stability of the whole system. Therefore, how to raise the output efficiency of PV cells and the charging level of the energy storage will be solved by this paper.Aiming at the above problems, this paper has carried out the research and design of the PV charging controller based on MPPT, which contains the following contents:Firstly, Starting from the basic theory of this paper, the basic principle and feature of PV and storage battery will be analyzed and Simulink is employed to build the simulation model of PV battery, Meanwhile the output characteristics of photovoltaic cells and the charging and discharging characteristics of the battery are studied. And the ways of charging the storage battery will be compared to propose the improving methods of charging combined with MPPT control.Secondly, The maximum power point tracking (MPPT) algorithm for photovoltaic cells is studied in accordance with the problem of the output characteristics of photovoltaic cells. Firstly, the MPPT principle and the common tracing algorithm are analyzed. Secondly, the simulation model is established in Simulink to compare the tracking effect of the maximum power Point tracking algorithm for PV cells. Finally, an improvement is proposed which combines the constant voltage method and perturbation observation method to obtain a maximum power point tracing algorithm, and the simulation and the common method are still compared to observe the differences, which has great efficiency and stability.Thirdly, the whole scheme of charging controller is designed. According to the control demand of charge controller, hardware circuit and software process are designed using ATmega128 single chip computer, and the key parameters of the main circuit are calculated. Besides, main control circuit, DC/DC conversion circuit, drive power circuit, signal collection circuit, protection circuit, display circuit are also devised. The system control flow, charging method selection procedures, termination of charging procedures and discharge protection procedures are designed in the Software.Fourthly, the designed charge controller based on MPPT is tested by data analysis. The charging effect of this charge controller proves to be better and meet anticipated expectation, and the maximum power point tracking of photovoltaic cells and the fast and efficient charging of batteries are realized as well.