Further load reductions with individual pitch control

TLDR

Individual pitch control can significantly reduce fatigue loading on wind turbines by adjusting each blade’s pitch in response to measured loads. This study adds a simple modification to the individual pitch control algorithm to lower the dominant load peak on fixed components, aiming to cut overall fatigue loads. The algorithm measures asymmetrical out‑of‑plane rotor loads and computes an additional pitch action per blade, dominated by rotor frequency, to minimize these loads. The modification nearly eliminates the 1P peak in the rotor load spectrum, cutting fatigue loads by 20–40%, while only modestly reducing low‑frequency loads on the nacelle and tower due to the 3P peak remaining largely unaffected. © 2005 John Wiley & Sons, Ltd.

Abstract

Previous work has demonstrated that significant reductions in fatigue loading on a wind turbine can be achieved by using individual pitch control, in which the pitch of each blade is adjusted individually, in response to measured loads. The asymmetrical out-of-plane rotor load is measured and an additional pitch action (dominated by the rotational frequency of the rotor) is calculated for each blade in order to minimize this load. This results in the near-elimination of the dominant once-per-revolution (‘1P’) peak in the out-of-plane load spectrum seen by the rotating components, and fatigue loads can be reduced by 20%–40%. The load reduction is also transferred to the nacelle and tower, but here it is the low-frequency loads which are removed, resulting in a load reduction of a few per cent at best, since the fatigue on the fixed components is dominated by the peak at the blade passing frequency (‘3P’ for a three-bladed turbine), which is largely unaffected by the individual pitch control action. This article demonstrates a relatively straightforward addition to the individual pitch control algorithm which is capable of reducing the dominant load peak on the fixed components, resulting in significant fatigue load reductions on the whole structure. Copyright © 2005 John Wiley & Sons, Ltd.