Large-scale Wind Turbines Independent Hydraulic Pitch From The System

Wind energy is a clean and sustainable energy and has become an important part of the strategy of sustainable development in many countries. With the wide using of wind power, wind turbine technology updates a lot, such as from stall control to variable pitch control, from fixed speed to variable speed and constant frequency, from transmission technology of the gear box to gearless driving and hybrid driving technology. Since the variable-pitch control was one of the key techniques in big-size wind turbine, this thesis applies theoretical analysis, simulation analysis and experimental validation to the study of the electro-hydraulic proportional hydraulic variable-pitch control system.Firstly, based on the aerodynamic analysis of wind turbine, the variable-pitch control strategy of the wind turbine was derived. It also changes the traditional variable-pitch approach driven by the crankshaft swinging bar mechanism, and designs the live hydraulic variable-pitch mechanism driven by the swing block mechanism. The thesis figures out the needed thrust pitch of the wind turbine under extreme operational conditions through the theoretical analysis, and designs variable-pitch hydraulic system.Secondly, it establishes the mathematical model of the electro-hydraulic proportional variable-pitch control system, in case that the blade of wind turbine was turned on or off. By the simulation of Matlab/Simulink, it analyzes the static and dynamic characteristics of the system under the two different conditions. Based on Ziegler-Nichols method, it determines the coefficients of the proportional amplifier and then optimizes the dynamic property of the variable-pitch system. The simulation model of wind speed, rotor, driven system etc. have been built. It also builds the simulation model of the wind turbine system. Under different wind conditions, it simulates the entire wind turbine system, so as to obtain the changes of wind turbine in the process of adjusting the pitch of blade.Finally, combing the virtual wind machines, it builds the testing table of electro-hydraulic proportional hydraulic variable-pitch system to carry out the combination simulation. The simulation and experimental results proved that the designed pitch control system can meet the normal operation of wind turbine. Gain scheduling PI controller, which can compensate the nonlinear aerodynamic characteristics of the wind turbine, makes the maximum wind capture of the wind turbine in low wind speed and output power under high-speed stable.