An efficient power control strategy for active mitigation of blade in-plane fatigue loading in PMSG-based wind turbines

This paper assesses the dynamic performance of permanent magnet synchronous generator-based wind turbine (WT) regarding the blade in-plane fatigue loads once the WT is controlled in power control mode. Blade in-plane oscillations, associated with the poorly blade in-plane modes, can be excited by turbulent winds or grid disturbances that may lead to damage of the blades and reduce the drive-train reliability. To overcome this drawback, at first, a model with three degrees of freedom is extracted for the drive-train system, and then, an active mitigation approach is proposed to mitigate the blade in-plane oscillations. The proposed method can effectively suppress the blade in-plane vibrations by adding a supplementary term into the power control loop that is proportional to the speed difference between the blade and generator. The speed difference between the blade and generator is obtained by estimation of the blade-hub and hub-generator shaft torsional torques. Next, the performance of the proposed active mitigation approach is examined by the modal and frequency response analyses and time-domain simulations. Finally, it is shown that the proposed approach has superior performance over the conventional approaches based on the simplified drive-train model and crossing the measured generator speed through a band-pass filter.