Study On Maximal Wind Energy Capture And Grid Conection Of Wind Generator System

Following high-speed economic development, the demand of energy is increasingcontinuously, the natural resources on the earth have faced a depleted crisis in recent years.In such a severe situation, every country in the world has proposed sustainabledevelopment, energy efficiency and environmental protection strategies. Along with therapid development of wind-power technology, many new types of wind power generatorshave been produced. The wind power as one of the most potential energy resources hasbeen got more attention. Therefore, the paper takes the variable speed variable pitch windgenerator as the object, which carries out research on how to improve the efficiency ofwind power, capture maximum wind energy and control grid-connected inverter.Based on the structure and the working principle of the variable speed variable pitchwind generator for wind energy utilization and the dynamic stability of the high demandcharacteristics, a linear parameter varying(LPV, Linear Parameters Varying) systemmodel is established. A sufficient condition of the adaptive robust guaranteed costcontroller is presented and a new adaptive guaranteed cost controller (AGCC) according tothis sufficient condition is proposed. In this controller, the uncertain parameters of thesystem are estimated by using the adaptive method, then the estimated uncertainparameters and robust guaranteed cost control are used to design state feedback gain, andthe controller can meet a quadratic performance evaluation. The simulation results showthat, in terms of low or high wind speed, the controller has good dynamic characteristicand interference suppression capabilities．The mathematical model of permanent magnet synchronous generator is analyzed. Inorder to achieve the maximum wind energy tracking under the rated wind speed, themethod of sliding-mode control and fuzzy control combining is adopted. Based on this, anew adaptive fuzzy soft switching control method is presented. To achieve the goal ofmaximum-power tracking, the motor speed is changed with the wind speed to gainoptimum tip-speed-ratio under the rated wind speed by this method. The simulation resultsshow that the adaptive fuzzy soft switching control method can effectively achieve the maximum power capture under the rated wind speed, compensate for the nonlinear impactto the system, and improve the robustness and stability of the system.When the wind power system was connecting to the grid, the voltage fluctuationscaused by the failure, the unbalanced loads and other uncertainty factors are exist in thewind power system. According to this problem, a disturbance observer is designed tocompensate them, and the adverse effect is suppressed. Based on the theory of vectorcontrol, a nonsingular terminal sliding mode controller is designed, which made thequadrature direct axis current of grid-side inverter track the given value in finite time.High-order terminal sliding modes are utilized to eliminate the chattering, the trackingprecision is improved. Simulation results show that the method combining the disturbanceobserver with the high-order terminal sliding mode control has strong robustness againstthe outside disturbance and good dynamic performance.