Research On MPPT And Storage Control Strategy For Stand-alone Wind/photovoltaic Hybrid Generation System

With the rapid development of global economy and the continuous progress of human civilization, energy issues have become increasingly prominent. The fossil energy has become gradually exhausted. Wind and solar energy as a green and sustainable energy gradually develops into a strategic alternative energy with the generously support of the country and the continuous improvements in technology. Compared with the traditional non-renewable energy, wind and solar energy is not only pollution-free green but endless as well. Meanwhile, due to complementary in time and space, the wind/photovoltaic hybrid system has received the unprecedented development. The system topology structure, the maximum power tracking and storage control issues in the wind/photovoltaic hybrid generation system are investigated in this thesis.The concept, characteristics and the development of wind/photovoltaic hybrid generation system in home and abroad are firstly introduced based on the background of wind/photovoltalc hybrid system. The composition and basic principle of wind/photovoltalc hybrid generation system are further analyzed. The simulation models of the two subsystems are established respectively in the Simulink environment, and the properties are also analyzed. Then the maximum power tracking problem of wind power generation system and PV system are studied respectively. By analying the tracking principle and common tracking strategies of the two subsystems, a variable duty ratio step threshold search tracking method is studied for the PV system. Accordingly, a variable duty ratio step combining with disturbance and interpolation tracking method is studied for wind power generation system. The simulation model of two subsystems are established, and the control strategies are verified. Based on the double inputs Boost circuit, the simulation model of overall system is established and simulated by analyzing working process and characteristics. Finally, the working principle and characteristics of battery are introduced in detail by understanding energy storage function and type in wind/photovoltaic hybrid generation system. For the charging control of battery, the four-stage charging method is studied by analyzing common charging methods. The simulation model is established, its correctness and superiority are also verified.For improved MPPT method and charging control method, the simulation results show that it can get a good tracking result, improve tracking precision and speed, and reduce the oscillation of system in maximum power point and the cost of the system. The four-stage charging process is more close to the ideal charging process of battery, which is beneficial to prolong the service life and improve the performance of the battery.