Stabilization of floating offshore wind turbines by artificial muscle based active mooring line force control

Abstract

The floating offshore wind turbine (FOWT) promises the future penetration of wind power generation into deep water, while FOWT presents significant challenge for controls in terms of platform stability, power regulation and increased structural loads. With floating foundations, wind turbine control faces dramatic increase of degrees-of-freedom (DOF) to be controlled, thus resulting in under-actuation reality. It is thus critical to develop actuation schemes that are of low cost, low power consumption, high bandwidth and low design complexity. In this paper, an active mooring line force control scheme is investigated using linear actuators based a novel thermally-actuated sewing thread artificial muscle (STAM). The STAM actuator is proposed to consist of multiple bundles of twisted nylon fishing line or sewing thread. The proposed actuator is added to the junction between the mooring lines and platform bars of FOWT with tensioned-leg platform (TLP). Simulation models of STAM actuator is integrated to the mooring line model of NREL's FAST, and control simulations are performed on the 5MW WindPACT model. Simulation results of two load cases validate the effectiveness of this novel actuation scheme in stabilizing the platform motion and reducing the wind turbine loads.