Research On The Variable-pitch Control System And Servo Unit For Wind Turbine

With the worldwide extent of industrialization and urbanization, energy and environmental issues has become the exigent problem for human survival and development. Wind energy, as one of the renewable energy, is becoming the most promising energy. On one side, because wind energy has characteristics of low density, randomness and instability, the output power of the wind power generator are highly fluctuated; on the other side, the wind turbine wheel diameter continuously increases which follows with the increase of wind power generator capacity, that enlarger asymmetric force load of wind turbine,which caused by altitude, wind shear and turbulence. Pitch control technology can improve that two problems mentioned before, thus it is used widely. The study of control technology can enhance the safety of wind turbines, output power quality and overall system stability.Firstly, this paper analyzes the characteristics of wind turbine aerodynamics. Based on that, it tries to get a strategy of how to control wind turbine generator at different wind speeds, and then sets up mathematical model of the wind speed, wind wheels, drive systems and pitch operator. Subsequently, this paper has designed the variable pitch controller based on the PID control. The simulation result reveals that when the wind speed exceeds the rated wind speed, the output power of wind turbine can be limited in the vicinity of rated power by operating pitch controller. Finally, this thesis describes the structure of electric pitch servo system, and established the mathematical model of permanent magnet synchronous motor. The control strategy is studied in this paper also. The electric pitch servo system under upload is simulated; simulation results show that the servo system has good tracking performance. The software and hardware of pitch servo system have been designed in existing condition.