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ECN publication
Individual Pitch Control - Inventory
Published by: Publication date:
ECN Wind Energy 1-6-2005
ECN report number: Document type:
ECN-C--03-138 ECN publication
Number of pages: Full text:
30 Download PDF  


The loads on the rotor blades, drive-train and tower of horizontal axis wind turbines are caused for a significant part by the rotational sampling of turbulence, the tower shadow and the windshear. These loads depend on the azimuthal blade position and are approximately periodic in (multiples of) the rotational speed. It seems attractive to just add pure azimut dependent variations to the pitch angle of the individual blades. However, a small phase mismatch with respect to the tower shadow and windshear effect will cause higher instead of lower loads. Besides, the stochastic loads from the torationally sampled turbulence are not reduced at all.

This inventory study concerns the design and potential of individual feedback pitch control for 3 bladed wind turbines. In this approach the danger of mismatch is avoided and the stochastic blade loads are also reduced. A simple design model is derived for the parametrisation of the feedback loops for individual pitch control around one time the rotational frequency (1 p). Rainflow counts and power spectra obtained from time-domain simulations give an indication of the achievable reduction of loads. In addition, the concept of individual pitch control is extended to multiples of the rotational frequency (2p, 3p; multi-mode pitch control). Scoping calculations show a significant further reduction of blade loads as well as a reduction of 3p harmonics in tilt and yaw loads in the nacelle.

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