Research On Intelligent Control For Variable Pitch Wind Turbines

Due to continually diminishing reserves of normal energy sources and environment pollution,it is very necessary to develop wind power as its renewable and clean characteristic.Large scale wind turbines always have variable pitch,which can control output power by pitch regulating,and thus higher pitch control technology is required. Supported by the National Science Foundation of China Project 'Research on optimizing control strategy overall operating condition for variable wind turbine hybrid system(NO: 50677021)' and as a part of it,this thesis studies intelligent control technology for variable pitch wind turbine,including neural network,fuzzy sliding mode control and their applications on pitch control,primary contents and original contributions of this thesis can be summarized as follows:Firstly,power transfer relation,mathematic model and its vector control strategy of doubly fed induction generator(DFIG) is deducted.Armed at stable operating of DFIG, mathematic model and normal control strategy for AC-DC-AC converter is studied and a novel corresponding control strategy is proposed,in which control voltage node is selected as load fed-forward position.Simulation indicates that DC-bus voltage regulating speed is increased by novel strategy.Research and improvements on DFIG exciting control strategy make generator system possess fast and stabile electric torque response ability,which supply precondition for variable pitch control technology studying.Secondly,DFIG and wind turbine control strategies for cutting-in are analyzed. DIFG cutting-in vector control system can make generator stator voltage meet cutting-in requirement with varied rotor speed,but can't maintained rotor speed.Therefore,based on startup characteristic and cutting-in speed control requirement of wind turbine studying,a novel pitch control strategy for cutting-in speed,with neural network identification and model predictive control,is originally proposed.Simulation shows that the nonlinear and disturbance problems are solved by novel strategy,whose control performance and anti-disturbance ability is superior to normal PI controller.Thirdly,according to variable pitch wind characteristic and control requirements,a novel pitch control strategy based on neural network model fed-forward,is originally proposed for power control during high wind velocity.Wind turbine model is established by neural network and used as fed forward for closed loop control system to deduce influence of wind varying.Simulation indicates its efficiency.Fourthly,form the view of enhancing control system robustness,a novel fuzzy sliding model control strategy is proposed for pitch control,with advantage of plant model is unnecessary.Adopting feedback linearization,a fuzzy sliding mode controller is constructed combining fuzzy control with sliding mode control.By using fuzzy logic to estimate uncertainty model in control law,slide mode control law is deduced to perform effective control,and stability is proved by Lyapunov function.Simulation proves its good control performance.