Control of a Floating Wind Turbine on a Novel Actuated Platform

Abstract

Designing a floating offshore wind turbine (FOWT) controller requires solving engineering challenges not found for fixed-bottom turbines. This paper applies several methods from the growing body of FOWT control literature to the 10-MW Ultraflexible Smart FLoating Offshore Wind Turbine (USFLOWT) baseline generator-speed controller. US-FLOWT aims to reduce capital expenses using the lightweight SpiderFLOAT platform, a novel smart floating substructure with built-in distributed actuators for direct platform tilt and heave control. In this work, the USFLOWT baseline controller is improved through detuning and parallel compensation with both blade pitch and generator torque. The SpiderFLOAT platform additionally allows motion compensation through distributed platform actuators. Two proposed SpiderFLOAT actuator types are considered for active platform control: a lowbandwidth actuator that uses variable floater ballast to bring a heeling platform to a steady-state upright position, and a highbandwidth actuator that dynamically changes the substructure geometry to actively reject transient platform motion. Each control approach is tested for USFLOWT using the open-source aero-hydro-servo-elastic wind turbine simulation tool Open-FAST. Performance results for each approach are compared across a range of above-rated wind speeds, and promising combined approaches are further evaluated to recommend future multi-parameter optimization pathways.

Damping analysis of Floating Offshore Wind Turbine (FOWT): a new control strategy reducing the platform vibrations

“…Controllers described by the literature considering the same compensations (Abbas et al, 2021;Stockhouse et al, 2021) aim at maintaining ω steady near its rated value by acting on the blade pitch β to variate the aerodynamic torque τ a with the opposite sign with respect to the rotor relative speed ω. However, this strategy neglects the following phenomenon: the blade feather modifies the aerodynamic thrust F a .…”

“…25 forecasts which operating points it affects. On the other hand, a wise choice of τ g avoids β → ω NMPZ, which is the main reason why this compensation has already been introduced by Stockhouse et al (2021) and in the control model in Section 2.1.…”

“…The strategy is such that k β is a negative number instead of what is proposed in the literature. In (Stockhouse et al, 2021),…”

“…It is to solve the Non Minimum Phase Zero (NMPZ) effects caused by the blade pitch on the rotor rotational dynamics. It is already introduced in (Stockhouse et al, 2021) and it is, in this work, analytically developed. The study of the NMPZs brings to a new NMPZ phenomenon, described for the first time in this work.…”

“…2.1 allows one to avoid NMPZ by choosing a well-suited value of k τg . This compensation has been already introduced byStockhouse et al (2021) with the formula:…”