Variable Pitch Angle Researching For Direct Driven PMSG-based Wind Energy Conversion System

Wind power is free, clean, and renewable. Wind energy is very abundant and widely distributed on earth. With the pressing situation of shortage of traditional energy and environmental pollution, to develop clean and renewable energy resources, especially wind energy is of prominent importance and it has become an important part of world's sustainable development strategy. Wind power generation technology is relatively mature, and wind power generation is one of the most prospective new energy developing programs. Control technology in wind power generation plays an increasingly important role. In order to make the output power constant, this paper focus on rotational speed control research for PMSG (Permanent-magnet Synchronous Generator)-based wind energy conversion system (WECS) above rated wind speed, using gain scheduling and feedback linearization method.On the basis of the analysis of the system parts'mathematic model, the nonlinear equivalent model of PMSG-based wind energy conversion system was established. In order to make the output power constant above rated wind speed, taking the power deviation as the input signal, a fuzzy PID controller was designed based on fuzzy domain and fuzzy rules that were abtained from practical experience. Simulation model was constructed in Matlab/Simulink and the controller was designed using S-function.In order to overcome the shortcomings of fuzzy PID controller that fuzzy rules are obtained from practical experience and the output of the system is prone to overshoot, taking the power deviation as the input signal, an auto disturbance rejection controller was desgined for the wind power system. The mathematical analysis was undertaken on a balance point when the system was operating on constant output power model. So the differential between the adjusted rate of pitch angle and power deviations was obtained as the control law. Finally, the simulation is undertaking under random wind. Simulation results indicate that the controller can effectively control the pitch angle, so the goal of constant power output of the system can be achieved.