Study Of Pitch Control Based On Electro-Hydraulic Servo System For A Variable-Speed Wind Turbine

Wind energy is kind of renewable energy. Since the energy crisis in 1973, wind power generation, as a way of the exploitation of wind energy, has been paid more attention by human being. Now days, Larger, VSCF (Variable-speed constant-frequency) and pitch control technology is the new trend of wind power generation technology. For the demand of pitch control of larger wind turbine, a pitch control method for a variable-speed wind turbine is proposed. According to mis method, the pitch angle of wind turbine blades is adjusted by using electro-hydraulic servo valve to control the hydraulic cylinder. The actuating mechanism for the pitch adjustment of wind turbine is designed and the electro-hydraulic servo position control system of pitch control is established. Based on the Lab VIEW virtual instrument, the test and control system is developed and the control experiment with PID algorithm for the displacement of hydraulic cylinder has been done.Firstly, the dynamic characteristics of wind turbine is analyzed based on theprinciple of aerodynamics, the expression of wind power coefficient C_p is deducedand pitch control principle of wind turbine is explained in theory; because the pitch control technology of wind turbine demands large power and quick response, the structure of hydraulic servo valve—servo hydraulic cylinder—pitch control of wind turbine is proposed.This paper puts forward the way and demand of design the pitch control mechanism, and the virtual pitch-controlled wind turbine model is built by Pro/E, the kinematics characteristics of wind turbine is simulated in the "Mechanism" environment of Pro/E.After describing the construction of a Variable-speed Pitch controlled wind turbine, the mathematics model of each part of the system is established, and the speed controller is designed for the purpose of pitch control, the simulated model of the wind turbine system is built by the tool of Matlab/simulink. The results testify the feasibility of pitch control system.The pitch-controlled electro-hydraulic servo system for a variable-speed wind turbine is established. The experiment system consists of Industrial Computer, PCI2006 data acquisition card, SVA-II servo amplifier, QDY type Electro-Hydraulic servo valve, hydraulic cylinder, GA-150 type high-precision displacement transducer and link mechanism. The real time control software and operation flat form is edited based on the graphic language in the Lab VIEW Virtual instrument.At last, with the electro-hydraulic servo testing equipment, a PID control algorithm is programmed with G language in Lab VIEW. The displacement curve of actuator is displayed in the computer, Experimental results show that the PID control algorithm is obviously effective and the high-precision of position control has gotten.Electro-Hydraulic servo system; Pitch control; Wind turbine; Position control; PID algorithm; Lab VIEW virtual instrument...