Leveraging Wave Power for the Stability of Offshore Floating Wind Turbine

Abstract

Floating Offshore Wind Turbines (FOWTs) face cost challenges driven by the large structural mass required for stability; as a result the Levelized Cost of Energy (LCOE) of electricity from FOWTs can be high. Aiming to reduce the foundation mass, this paper investigates active stabilization leveraging wave power in a Wave-Augmented Floating Offshore Wind Turbine (WAFOWT) device in which three Oscillating Water Column (OWC) chambers, embedded in the foundation, provide control torque. By controlling the air mass flow through chamber valves, it is possible to create a differential torque about the platform pitch axis. A dynamic model is presented that couples the platform rigid-body dynamics with the chamber pressure dynamics. A Hamiltonian-based Sliding Mode Control (SMC-H) strategy is proposed in this work; this control approach uses the system’s Hamiltonian as a sliding surface in the sliding mode control to achieves a balance between stability and optimality. Simulation results in a representative regular sea state demonstrate that the proposed SMC-H controller significantly reduces platform pitch motions compared to passive operation and linear quadratic control benchmarks.