Optimal control of a ballast-stabilized floating wind turbine

Abstract

Offshore wind energy capitalizes on the higher and less turbulent wind speeds at sea. The use of floating structures for deeper waters is being explored. The control objective is a tradeoff between power capture and fatigue, especially that produced by the oscillations caused by the reduced structural stiffness of a floating installation in combination with a coupling between the fore-aft motion of the tower and the blade pitch. To address this problem, the present paper models a ballast-stabilized floating wind turbine, and suggests a linear quadratic regulator (LQR) in combination with a wind estimator and a state observer. The results are simulated using aero elastic code and analysed in terms of damage equivalent loads. When compared to a baseline controller, this controller clearly demonstrates better generator speed and power tracking while reducing fatigue loads.