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Scientific presentations at FOWT 2023

In addition to the project's participation in the Floating Offshore Wind Turbines (FOWT) 2023 conference in Nantes, two researchers working on FLOATECH will give presentations on their work within the project.

Both will take place during the second Technical Session on FOWT design tools, digital twins & control optimization which will take place Thursday 11 May from 11:10 to 12:20.

Vincent Leroy from the LHEEA of Ecole Centrale de Nantes will present a paper entitled "Wave basin experiments coupled with aerodynamic numerical simulations for FOWT studies", and Amr Hegazy from TU Deflt will give a presentation about "Rejecting wave disturbances on floating wind turbines".


Wave basin experiments coupled with aerodynamic numerical simulations for FOWT studies

Authors: Vincent Leroy, Félicien Bonnefoy Sylvain Delacroix

The study of floating structures and their mooring setup makes use of wave basin experiments e.g. in complex situations such as extreme waves to validate the state-of-the-art offshore models and/or to calibrate physical effects such as damping or nonlinear effects. Concerning FOWT, the wind loads play a key role on the system dynamics and they need to be included in the wave basin tests for completeness.

To that respect, approaches like Real-Time Hybrid Model testing (aka Software in The Loop) combine numerical simulation of the turbine with imposed motions from the experiments and physical tests in the wave tank with actuated force from the simulation. In other words, a parallel execution of experiment and simulation, with bidirectional data transfer coupling. Both parts are in the appropriate similitude and hence with the correct physics, Froude similitude in the tank and Reynolds similitude in the numerical model. The latter includes turbulent wind and induction.

We will present the SIL system developed at LHEEA and its performance to address the influence of both the aerodynamic loads acting on the servo-controlled turbine and the hydrodynamic loads on the floater response and the mooring line tensions. In the aerodynamic model, we use different wind turbine controllers that we call as an external library. We can address the corresponding influence on the floater response in the low frequency regime, as well as correct trim angle vs wind speed, aerodynamic damping and other effects of aerodynamic loads. Results from the FLOATECH project will be presented.

Rejecting wave disturbances on floating wind turbines

Authors: Amr Hegazy, Peter Naaijen, Jan-Willem van Wingerden

The design of control strategies for floating offshore wind turbines (FOWTs) is even more difficult than for the fixed-bottom ones due to the addition of the extra dynamics from the floating platform. Moreover, there is a current lack of recognized control strategies for FOWTs. In order to design effective control strategies, the additional dynamics introduced by the floating platform should be considered during the controller synthesis stage. And when it comes to industry, feedback control strategies are the ones mostly adopted in the control of wind turbines. The usage of control in rejecting environmental disturbances; mainly wind turbulence is starting to gain more attention nowadays in the wind turbines industry with the exploitation of LiDAR measurements for wind disturbance rejection. But what about waves?! Especially with the huge support, from the European Union, for the development of Floating Offshore Wind Turbines (FOWTs). For the goal of investigating the potential gain of wave disturbance rejection, a novel control strategy where the conventional feedback controller of the FOWT is complemented with a feedforward controller, with the sole objective of rejection the wave disturbance. The feedforward controller utilizes a real-time forecast of the wave obtained from an upstream measurement to compute a control action. The wave-feedforward strategy is first proved considering the objective of reducing the rotor speed oscillation caused by the waves in order to increase the power production. Accordingly, a feedforward controller is designed for this goal and its performance is examined by means of linear analysis. The feedforward control strategy is tested on a 5MW floating wind turbine, complementing the standard feedback controller for generator speed regulation. Numerical simulations are carried out in the wind turbine simulation suite, OpenFAST, in several operating conditions with realistic wind and waves, demonstrating that the proposed feedforward controller effectively mitigates the effects caused by waves.

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