Experimental analysis of the scaled DTU10MW TLP floating wind turbine with different control strategies

Abstract

The experimental testing of a Tension Leg Platform (TLP) floating wind turbine at 1:60 scale in wind and waves with a pitch-regulated 10MW wind turbine is presented. The floating wind turbine was tested with three different control configurations: two closed-loop controllers and one open-loop controller. The experimental setup and program is described in this paper, and system identification and the responses of the floater to hydrodynamic loading are analysed and compared for the different control strategies. It was observed that negative aerodynamic damping for the onshore controller resulted in high oscillations in blade pitch, yielding an increased response in surge for all wave types. It was also observed that the surge motion governed the mooring line tensions, thus the onshore controller yielded the highest tensions in the front mooring line. Further the shutdown cases of the offshore controller led to larger surge displacement when the shutdown was initialized right before the wave impact.

Characterization of the unsteady aerodynamic response of a floating offshore wind turbine to surge motion

“…Whilst in Froudescaled models (e.g. Goupee et al, 2017;Madsen et al, 2020) the blade pitch is typically adjusted in order to cope with the steady thrust reduction due to lower Reynolds numbers, here a different approach was followed for better aerodynamic accuracy. Given that the dimensions were scaled by a factor of 75 to fit in the wind tunnel, and the wind velocity was scaled by a factor of 3 for surge actuation purposes, the Reynolds number was 225 times lower than in reality.…”

“…HYWIND TM ) are more prone to pitching, whilst both semi-submersible (e.g. WindFLoat TM ) and tension-leg platforms (TLPs) are particularly affected by surge oscillations that also drive the tensile load on the mooring lines (Madsen et al, 2020). In addition, small pitch rotations are often linearized to surge displacements to simplify the aerodynamic modelling.…”

“…Apart from some tests on very small turbines (Farrugia et al, 2014;Sant et al, 2015;Khosravi et al, 2015), from which it was hard to draw any full-scale conclusion, a validation campaign on a 1 : 60 scaled version of the NREL 5 MW RWT was conducted by Ren et al (2014), but the interest was mainly on the hydrodynamic loading, and the surge motion was considered an output. Similarly, Goupee et al (2017) and Madsen et al (2020) carried out plenty of tests to address the impact of the control strategy on the motion of different platforms. Nevertheless, it is very difficult to understand the influence of the unsteady aerodynamics from combined wind and wave tests.…”

Characterization of the unsteady aerodynamic response of a floating offshore wind turbine

“…At MARIN's offshore basin Goupee et al (2017) carried out intensive testing of a 1:50 model of the NREL5MW, mounted on a semi-submersible platform, specifically focusing on control aspects. More recently, Madsen et al (2020) performed similar experiments on a 1:60 model of the DTU10MW RWT mounted on a TLP, investigating the system's response to various wind and waves conditions with different control strategies. Nevertheless, it is very difficult to understand the influence of unsteady aerodynamics from combined wind and waves tests.…”

“…As side benefits, also a valuable comparison among the different fidelity models for wind turbine aerodynamic modelling along with a robust result nondimensionalization strategy have been produced. Goupee et al, 2017;Madsen et al, 2020) in order to cope with the steady thrust reduction due to lower Reynolds the blade pitch is typically adjusted, here a different approach was followed for a better aerodynamic accuracy. Provided that the dimensions were scaled by a factor 75 to fit in the wind tunnel and the wind velocity was scaled by a factor 3 for surge actuation purposes, the Reynolds number was 225 times lower than reality.…”