Study On Some Key Problems Of Control System For Wind Turbine

Based on the research on the wind turbine system, this dissertation sets the power and loads control as objects and further puts forward corresponding control strategies. On the basis of analyzing and establishing the model of wind turbine, the dissertation makes in-depth research on the control strategies about the optimum power control below rated wind,pitch control above rated wind , predictive control of power, and the reduction of the loads. Then, with the employment of those proposed control strategies and methods, it makes simulation design for the control system of wind turbine. The following are those main points of this dissertation.In chapter 1, the research background was introduced, the significance of the research was expounded and those research situation of wind turbine were summarized. Besides, the control strategies and control algorithms were especially emphasized. Then, the main content and structure of dissertation were recommended.In chapter 2, according to the wind turbine dynamic inflow theory, the unsteady inflow model was created. Then, the rationality of the establishment of wind turbine model by employing the dynamic inflow theory was analyzed. Furthermore, the influence of wake on the dynamic features of wind was indicated. And the acceleration potential method of unsteady flow was modified. Besides, based on the theory of von Karman, the turbulent wind model was set up and the three-dimensional turbulent wind field was gained. Finally, by comparing the analysis results between Matlab simulation model and Bladed design model, the correctness of aerodynamical model of wind turbine that has been proposed was validated.In chapter 3, on the basis of analyzing the features of performance of wind turbine, three districts were divided in the process. Then the corresponding control strategies of the three districts were designed owing to the difference between different districts. Focusing on the research on those control strategies in full loads period, the smooth transition of control by decoupling the control loop was realized. Then, based on the characteristic of the system, the performance of control system would be improved by combining predict control method to reduce time lag of system. Besides, with the combination of characteristics of wind turbine, by analyzing the model predictive control algorithm of linear state space, the model predicative controller of the system was designed. Afterwards, the model predictive controller was divided into three modules including disturbance model, object calculation and dynamic optimization. Then, based on the analysis of the features of those modules, their mathematical model was established. At last, with the exertion of the emulation mode, the advantage of model predictive control on power control of wind turbine was validated.In chapter 4, the linearization method of wind turbine was analyzed and the three states linearization model was selected as control objects according to the research focus of this chapter. Based on the analysis of single neuron, the mathematical model of single neuron was deduced and its algorithm was ameliorated to attain the improved the mathematical model of single neuron. Then, by adopting the improved control algorithm to adjust conventional PID controller parameter, the self-adaptive PID controller which was based on the improved single neuron was gained. Then, the gained controller was used to regulate pitch system and comparative analysis of the functions of the two controllers in system was made.In chapter 5, based on kinematic equation, the filters in fore-afterward direction and in sideward direction were designed to increase damping and reduce vibration. Furthermore, by increasing damping for train and shielding the crossover frequency of blade, the resonance between tower and rotor was avoided. Next, the multi-blade coordinate transformation theory was analyzed and the method of independent pitch control was combined and kinematic equation of rotation coordinate was converted to fixed coordinate in individual pitch control. Thus, the design process of individual pitch was simplified. Then, the results were converted to rotation coordinate via inverse transformantion. And finally, the physical quantity was integrated with output of power control loop to become the input of pitch control of wind turbine, which could effectively reduce uncertain loads.In chapter 6, the conclusion of the major research contents and results was achieved and the task that should be accomplished further in the future was also advanced.