Platform Stabilization and Load Reduction of Floating Offshore Wind Turbines using Dynamic Vibration Absorbers

Abstract

Floating offshore wind turbines (FOWT) are subject to significant increases in structural loads due to the platform motion under turbulent wind and wave. The under‐actuation challenge in FOWT control demands for development of extra actuators for platform stabilization. For FOWT with tension‐leg platform (TLP), this paper presents a comprehensive study on design and control simulation for realizing active mooring line control via the deployment of vertically operated dynamic vibration absorbers (DVAs) at the spokes of TLP structure. The DVA is designed based on the suppression of the primary modes of platform pitch and roll motion. In addition to the enhancement of FAST‐based simulation module, an 11 degrees‐of‐freedom (DOFs) control‐oriented model is derived for the TLP‐FOWT‐DVA system. Based on the control‐oriented model, a linear quadratic regulator (LQR) controller is designed. Simulations are performed for 9 m/s and 18 m/s turbulent winds with different wind and wave directions. The wind turbine performance, platform motions, and structural fatigue loads are evaluated. The results show that the platform motion and tower loads in the lateral direction are significantly reduced, while the tower load in the fore‐aft direction can be moderately reduced. Also, significant reduction in the mooring line tension loads is observed. For achieving the performance in platform motion stabilization and load reduction, the average power consumption of the DVA actuators is less than 0.27% of the wind turbine power generated during the simulated periods. The figures of merits promise significant potential for the feasibility of DVA based control for TLP‐FOWT.

Platform stabilization and load reduction of floating offshore wind turbines with tension‐leg platform using dynamic vibration absorbers

“…Tuned liquid column damper (TLCD) has been investigated theoretically and experimentally, and it is very effective to damp the oscillation of platform surge. However, as for TLP, tower load is more closely related to platform pitch and roll rather than surge and sway. As the TLP is mainly balanced by the tension forces of mooring lines and the buoyant force, active mooring line tension control is an effective way to control the platform motion.…”

“…Nihei et al conclude that the TLP shows the best performance by experimental evaluations for four platforms using scaled models . Despite its good performance in suppressing tower load increase, there remains room for TLP to further decrease the tower loads by deploying actively controlled dynamic vibration absorbers (DVAs) on the platform or the semiactive TMD in the nacelle . The advantages of using DVAs for platform motion stabilization include simplicity in structural design, cost‐effectiveness in deployment, and consistency in performance with properly designed controllers.…”

“…Based on the authors' previous work, this paper presents a more in‐depth study on DVA‐based TLP‐FOWT control, in terms of the design of passive DVA, dynamic modeling of TLP‐FOWT‐DVA system, active DVA controller design, and performance evaluation. The remainder of this paper is organized as follows.…”

“…32 Despite its good performance in suppressing tower load increase, there remains room for TLP to further decrease the tower loads by deploying actively controlled dynamic vibration absorbers (DVAs) on the platform or the semiactive TMD in the nacelle. 27,33,34 The advantages of using DVAs for platform motion stabilization include simplicity in structural design, cost-effectiveness in deployment, and consistency in performance with properly designed controllers. In addition, installation of DVAs at the spokes of TLP, rather than inside the platform or tower top, requires limited modifications to the platform or wind turbine.…”