Research On Wind Energy Conversion System And Control With Brushless Doubly-Fed Generator

Energy, the basic requirement of the human life, is also the material foundation to the national economical development. Energy safety has become the guarantee of the national economical safety. Energy shortage, especially the fossil energy shortage, has become the bottleneck of the China economical development. In view of the energy strategy, we need to find a sustainable way for the energy strategy. Among all the renewable energy and new energy technological development, wind power is the most potential one. It has the ability to compete with the fossil, nuclear-powered and other resources in the technology and economics. With the popularization of the MW-class wind power generator, it requires us to do research on the dynamic performance of the wind turbine, and to design more accurate control system for the novel wind power generation system at a low cost.The dissertation, in the view of sustainable energy development, discussed the great importance of the wind power in the future energy development. According to the detailed data, we have introduced the utility of wind energy in the power systems. The survey of the wind power generator production,research in domestic and abroad has been done.The dissertation introduced many basic principles of advanced control methods as well as applications in such field as: maximum wind power point tracking,power quality,fatigue of the transmission train,vibration of the lamina,bending of the tower, some problems needed to be resolved are presented. The author's main innovative researches are as follows:The brushless doubly-fed machine (BDFM) is actually a class of asynchronous AC excitation synchronous machine. From the basic principles of AC machine, theoretic prove of BDFM was given in this dissertation.The slip problem of BDFM is discussed as in induction machine(IM). The explicit definition and simplified calculation of slip of BDFM were given. The corresponding concepts of the BDFM have been unified. On the basis of the basic principle and design method of asynchronous machine, we presented the design method of the BDFM. Some key design problems were given.The BDFM has two sets of winding with different pairs at its stator. As these two sets of winding have no direct coupling relation, the average torque can not be obtained.The transmission of the electromagnetism power between two stator winding must be only obtained by a special structure rotor. Its dynamical and static state analysis is a little different from that of the ordinary asynchronous machine. The pole pairs and the current frequency of power windings,control windings and rotator are all different. From the basic principles of the AC machine,using the equivalent analysis method, a series of the equations,vector diagram,equivalent circuits of BDFM were obtained, which is the foundation of the analysis and control of the BDFM wind power generation system.The variable structure control(VSC) was first used to the active and reactive power decoupling control of the BDFM.Based on the state equations, the control law was get by the Lyapunov method. Simulation results showed that the VSC method can not only realize the active and reactive power decoupling control of the BDFM, obtaining the maximum wind power capture, but also can adjust the reactive power of the electric grid to satisfy the requirements of the electric power system.A fuzzy logic control method for a variable speed adjustable-pitch wind energy conversion system(WECS) is presented. The fuzzy controller is used to track the optimal tip speed ratio when the wind speed is below the rated value. The adaptive fuzzy controller is used to maintain a stable power output. The input is the rotating speed instead of the wind speed.Comparing to the traditional PID controller, this method can reduce the vibration efficiently and get to stability much more quickly, so as to improve the efficiency and quality of the wind energy conversion system. The application of the wind power generation system based on the BDFM can regulate the speed and realize the variable speed constant frequency control, greatly improving the control performance of the wind turbine.In dissertation, a kind of novel dynamic simulation method of wind turbine(WT), which can overcome the disadvantages of the present simulator, is presented based on direct torque control of induction machine. With this method, the simulator could simulate the dynamic wind turbine and don't need to change mechanical equipments when simulating different wind turbine, and just need to change the parameters of the software. Till now, all the simulating methods are directly simulating the pneumatic torque of the wind turbine. The output torque of the electric machine is made to equal to the output pneumatic torque of the wind turbine. We need to equip mechanism with the same inertia as the wind turbine simulator, when simulating the wind turbine dynamically. In this dissertation, instead of the pneumatic torque of WT, the acceleration speed of WT has been directly used to realize the simulation. According to the theoretical analysis of the BDFM, and on the basis of the wind turbine generation system in the lab, we have done some experiments. The results proved the characteristics of the BDFM. Detailed analyses were given to some special phenomenon found in the experiment, which gives a good foundation for the design and effective real-time control of the large-scale wind power generation system based on the BDFM.