Research And Controuing On Hydraulic Variable Pitch Drive Technology Of Large-scale Wind Turbine

In the case of the global energy crisis, wind energy is paid more and more attention by the world since it is a kind of sustainable and clean energy. Since the wind has the characteristic of lower density, random, instability and so on, it’s very important to carry a deep study in control technology of wind turbines especially in large scale sets. Thus, variable-pitch controlled system as one of the nuclear part of the total control system plays a important role in the efficient, stable and secure operation. Therefore, this paper carries out a full-scale analysis of the hydraulic pitch-controlled system.Firstly, the stress situation of blade is analyzed on the base of the Baez theory and the blade element momentum theory. Combined with the working state of wind turbine, the control law is deduced. Meanwhile, the block diagram of the pitch-control system is proposed along with the control process.Secondly, the paper compares two kinds of variable pitch actuator:electric pitch actuators and hydraulic variable pitch actuator which are popular currently at home and abroad. Single stage drive type hydraulic variable pitch actuator is designed. The paper also analysis the stress state of the mechanism and calculates the variable propeller load calculation. Thus advantages are embodied such as fast response speed, positioning precisely and so on. With the help of electro-hydraulic proportional control technology, hydraulic pitch control unit design is completed and the whole working state is elaborated.Furthermore, according to the characteristics of hydraulic variable pitch system, precise mathematical models are established aiming at two different conditions of increasing pitch and decreasing pitch. The system stability and stability degree is analyzed in the mean time. The dynamic performance of the system is analyzed by building the step response model in the simulink environment. According to the defects such as overshoot and slow response in the process of pitch decreasing, the paper builds the corresponding PID control model to improve its dynamic characteristics.Finally, this paper uses the various toolboxes of Matlab/Simulink to establish a whole machine model which contains various types of electrical, mechanical, hydraulic and air dynamics and other subjects. The model can visually reflect the dynamic characteristics of hydraulic variable pitch system, generator, power grid and gear box and so on. Research and validation of various operating conditions is realized to provide a strong guarantee for power control. The simulation results show that, the design of the hydraulic system and the established model is reasonable and feasible. The model can preferably meet the requirements of speed control and power control of wind turbine.