Sway vibration control of floating horizontal axis wind turbine by modified spar-torus combination

Abstract

Spar type floating wind turbines exposed to marine environment experience significant vibration, which is more prominent under wind-wave misalignment. This unavoidable vibration, particularly in the sway direction, affects overall performance and can induce significant damage to sensitive electro-mechanical components leading to downtime for maintenance. With this in view, the present study aims to propose a modified spar-torus combination by introducing spring and dashpot in between, so that it can work as an isolator. First, a comprehensive mathematical model for this multi-body system is developed using Kane's approach with proper aero-elastic and hydrodynamic simulation. For this purpose, 3D wind fields are generated in TurbSim and the waves are simulated from Pierson-Moskovitch spectrum considering wind-wave correlation and misalignment. Aerodynamic loads are computed using modified Blade Element Momentum theory while and hydrodynamic loads are generated using Morison's equation. Using these inputs, the response of the modified spar-torus combination is solved, which demonstrates the efficiency and advantage of the proposed vibration isolation. Different sea states and wind conditions are simulated replicating the actual scenario to investigate the performance envelope of the proposed controller for spar-type floating wind turbines.