Research On Power Track Optimization Control Strategy Of Direct-drive Wind Power System

With the continuous development of global economy, energy problem will also be intensified, the development and utilization of new energy will be also increased. Wind energy is a very important new energy, it has a big storage and fulls of high development value. Compared to other new energy technologies, the wind power generation technology is quite mature. However, the use efficiency of wind power should be better improved, which is still a key point in the research on wind power.Firstly, the status quo of wind power today is introduced and two kinds of mainstream models are analyzed in this dissertation. Based on some theory knowledge of wind turbine, the simulation model of wind turbine is established, and its power characteristics and output characteristics were analyzed. For the permanent magnet synchronous motor, its mathematics model and three control methods are introduced. Then, the theoretical basis of maximum power point tracking control algorithm is introduced. The principle of tip speed ratio method, power feedback method and climbing search method are presented in detail. In the introduction for climbing search method, the traditional fixed-step climbing search method, the climbing search method based on the double-step long and variable step search method of climbing are introduced. The basic principles and search process of the three algorithms are elaborated. Meanwhile, an improved climbing search method is proposed.Finally, the simulation model of wind power generation system is established under the environment of Matlab. The traditional fixed-step climbing search method, based on the two-step long climbing search method and improved climbing search method has been carried on the simulation analysis. The simulation results show that the improved climbing search method can quickly capture wind energy, the deviation between actual speed and best speed can be reduced, the mechanical oscillations at the maximum power point can be also reduced, the conversion efficiency of wind energy can be greatly improved. The control strategy of wind power system is introduced. The rectifier side control strategy and inverter side control strategy of wind power system is established and simulation analysis is made at last. The results show that the active and reactive power decoupling control is achieved. The good three phase current with less harmonics in this system can be achieved simultaneously, which is benefit for the grid connecting.