Analysis of tower/blade interaction in the cancellation of the tower fore-aft mode via control

Leithead, W.E. and Dominguez, S. and Spruce, C. (2004) Analysis of tower/blade interaction in the cancellation of the tower fore-aft mode via control. In: European Wind Energy Conference 2004, 2004-11-22. (http://www.2004ewec.info/files/23_1400_williamleit...)

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Abstract

With the increase in size of wind turbines, there is increasing interest in exploiting the pitch control capability of variable speed turbines to alleviate tower fatigue loads. The most direct method is to modify the blade pitch angle in response to a measurement of tower acceleration. It is shown that the ap mode has a central role in determining whether this approach is effective since there is a strong interaction between the blade ap-wise mode and the tower fore-aft mode. Several different approaches to the design of the controller for the tower speed feedback loop are investigated. It is concluded that a reduction in the tower loads of up to 18% is possible for multi-megawatt sized wind turbines.