Minimax Optimization of Fatigue Loads in a Wind Farm and its Realization Via Sliding Mode Controller of Wind Turbines

Operation optimization of a wind farm with robust fatigue load minimization is considered. Since wind turbines are installed as a firm in a restricted area, their interferences cause their mechanical fatigue loads. Thus their maintenance cost can be managed via fatigue load reduction. In this paper, this issue is solved by an optimization problem which minimizes the maximum fatigue load among turbines and gives reference points of pitch angle and tip speed ratio for each turbine. Furthermore, a super-twisting sliding mode controller for each wind turbine is proposed, which is robust to uncertainties of turbine and generator, as well as to electric grid disturbances. The sliding mode controller designs a continuous torque and improves the wind turbine performance by enhancing energy capture and reducing dynamic loads. Then the controller realizes operation on the reference points of each wind turbine. The effectiveness of the method is illustrated through a numerical example.