| Wind power is becoming more and more popular in the worldwide range, with its installation capacity 30% increasing annually. In China, the installation capacity of wind power generator has boosted from 1260MW in 2005, 2600MW in 2006, to over 5000MW in 2007. After a couple of years of development in the area of wind power technology, it has become mainstream to introduce variable pitch control methods and variable speed constant frequency technology into megawatt wind turbines. In this paper, an electro- hydraulic proportional pitch control system for megawatt wind turbine is studied through theory-discussing, solutions-designing and emulation by software.Basing on the Betz Wind Turbine Theory and Blade Element Momentum Analysis Theory, this paper firstly analyzed the blade's stress and determined the parameters of main components of hydraulic system through calculating the pitch-adjusting push force of a 1.5MW wind turbine under extreme running conditions. In this paper, the mathematical models of the hydraulic system are builded up respectively in the course of pitch-increasing and pitch -decreasing of the wind turbine, and the model is emulated by Matlab to analyze the response characteristics of the hydraulic system. In the last part of this paper, a new digital electro-hydraulic position servo controller is designed, which is suitable for Megawatt wind turbine pitch control system. The controller composed of Fuzzy-PID controller, ramp generator, variable dead zone compensator, PWM modulator and U/I voltage-current converter. In order to quicken the response speed to the wind velocity disturbance, a feed forward controller's design solution is brought into the pitch control system as well. Emulated by Matlab, the controller is proved effectively to control the position of the cylinder's piston.
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