The Study On Variable-Pitch Control Of Wind Turbines Based On Collaborative Ergulation Of Multiple Controllers

This thesis studies the operation of the wind turbine control strategies in windenergy conversion system(WECS). The aims of the research is to obtain a stable andefficient control strategy for large variable pitch wind turbines. The controller ofWECS should satisfy the characteristics of wind energy capture about the windturbine and the demand of grid. Below the rated wind speed, the speed of the windturbine and wind speed must be maintained at a constant speed ratio to ensure themaximum wind energy capture efficiency. Above the rated wind speed, the speed andtorque of the wind turbine should remain at the ratings by variable pitch control toensure a better quality of electricity and longer life of wind turbine. Therefore, as oneof the key technologies of large-scale wind turbine, the performance of the variablepitch controller directly affects the health and life of the WECS. Firstly, this thesisdescribes the basic working principles and energy conversion characteristics ofWECS. And the operational characteristics of all stages of the variable pitch andvariable speed WECS are discussed and analyzed. Then, a new control strategy isproposed.Below the rated wind speed, the angle of wind turbine is set at0°to capture themaximum wind energy. The torque of generator is controlled by PID regulation basedon generator’s speed feedback.Above rated wind speed, the regulation is no longer only based on speed feedbackor power feedback, but the two sum together. The wind speed signal is utilizedeffectively too. The variable-pitch control of wind turbine based on collaborativeregulation of Multiple Controllers is proposed. The first controller is PI pitchcontroller base on speed feedback regulation. The second controller is variableintegration PI pitch controller base on power feedback regulation. The third controlleris fuzzy feed-forward compensation controller based on wind. The reference of pitchof the entire system is the result of the three sum together. In addition, because of the0and torque is controlled based on speed feedback regulation, the PI controllerbased on speed feedback regulation plays a main role. The PI controller base onpower feedback regulation and the Fuzzy feed-forward compensation controller playauxiliary roles. Fuzzy controller is only affected by wind. The torque is kept at theratings by limiting.Then, the implementation process of the control strategy is presented, simulationanalysis and tuning of controller parameters are made in the MATLAB/simulink. Thesimulation results show good performance. At last, a simulation platform based onCANopen bus communication is established. And the variable pitch program of thehost controller is designed with the Beckhoff PLC.