Platform Stabilization of Floating Offshore Wind Turbines by Artificial Muscle Based Active Mooring Line Force Control

The floating offshore wind turbine (FOWT) presents underactuation challenge for controls in terms of platform stability, power regulation, and increased structural loads, which demands for simple, low-cost, low-power, and high-bandwidth actuation concepts. In this article, an active mooring line force control (AMLFC) strategy is proposed based on a novel thermally actuated fishing line artificial muscle (FLAM) actuator. The proposed FLAM actuator consists of multiple bundles of twisted nylon fishing lines, which is added to the junction between the mooring lines and platform bars of FOWT with tensioned-leg platform (TLP). A simulation model of the FLAM actuator is developed in Simulink, along with an interface to the mooring line model of TLP-FOWT in NREL's FAST. The dynamic model of the FLAM actuator is obtained with ANSYS simulation, and a control-oriented model is obtained for the FOWT platform motion. A linear quadratic regulator is implemented for the FLAM-based AMLFC. Simulations are performed on the 5-MW WindPACT model for one Region-2 and one Region-3 scenarios. Simulation results show that, with mild power consumption, the proposed strategy can significantly reduce the platform roll motion and the tower-base side-side bending loads without little impact on the rotor speed and power output.