Research On The Optimization Of Power Tracking Control Strategy For Large-scale Wind Turbines

As a renewable clean energy,wind power is of more and more importance.Due to the randomness of nature wind,the difficulties in wind turbine control have greatly increased,thus the maximum power point is hard to track using traditional control strategy,part of the wind energy has been wasted.Improving the power coefficient and realizing the maximization of output power have been a matter of concern.This thesis focuse on realizing the maximum power point tracking(MPPT)for doubly-fed induction generator(DFIG).The contents include:An effective wind speed estimator based on high-degree cubature kalman filter(HCKF)and newton-raphson method(NR)is proposed for the difficulty in obtaining effective wind speed using traditional control strategy;Further more,in order to improve the resistance of gross error,a robust HCKF method is proposed based on the Robust Estimation,and it is applied in the wind speed estimator.A speed controller and a current controller is designed based on NFTSMC,and the stability is also proved.O n this basis,the Tracking Differentiator is used for the estimation and compensation of system uncertainty to weaken t he chattering,the simulation results show that the proposed controller can meet the requirement of MPPT.An improved step strategy is proposed aiming at the problems caused by the unbalanced searching ability in global scope of Fruit Fly Optimization Algorithm(FOA).The strategy can adjust the moving step according to the optimal fruit fly position in current population dynamically,so the searching ability of FOA is balanced in global scope.Simulation results of several benchmark functions demonstrate that while ensuring success ratio,the step strategy also improves the convergence accuracy and the convergence speed of FOA.Then the modified FO A is applied in the parameter optimization of the controller,the results show the optimized parameters have better performance compared with the empirical parameters.Numerical simulation of the DFIG under rapidly change wind conditions has been carried out.The results show that the proposed strategy can estimate the effective wind speed accurately,achieve better MPPT compared with the traditional control strategy.