OC6 project phase III : validation of the aerodynamic loading on a wind turbine rotor undergoing large motion caused by a floating support structure

This paper provides a summary of the work done within Phase III of the Offshore Code Comparison, Collaboration, Continued, with Correlation and unCertainty project (OC6), under International Energy Agency Wind Task 30. This phase focused on validating the aerodynamic loading on a wind turbine rotor undergoing large motion caused by a floating support structure. Numerical models of the Danish Technical University 10-MW reference wind turbine were validated using measurement data from a 1:75 scale test performed during the UNsteady Aerodynamics for FLOating Wind (UNAFLOW) project and a follow-on experimental campaign, both performed at the Politecnico di Milano wind tunnel. Validation of the models was performed by comparing the loads for steady (fixed platform) and unsteady wind conditions (harmonic motion of the platform). For the unsteady wind conditions, the platform was forced to oscillate in the surge and pitch directions under several frequencies and amplitudes. These oscillations result in a wind variation that impacts the rotor loads (e.g., thrust and torque). For the conditions studied in these tests, the system mainly described a quasi-steady aerodynamic behavior. Only a small hysteresis in airfoil performance undergoing angle of attack variations in attached flow was observed. During the experiments, the rotor speed and blade pitch angle were held constant. However, in real wind turbine operating conditions, the surge and pitch variations would result in rotor speed variations and/or blade pitch actuations depending on the wind turbine controller region that the system is operating. Additional simulations with these control parameters were conducted to verify the fidelity between different models. Participant results showed in general a good agreement with the experimental measurements and the need to account for dynamic inflow when there are changes in the flow conditions due to the rotor speed variations or blade pitch actuations in response to surge and pitch motion. Numerical models not accounting for dynamic inflow effects predicted rotor loads that were 9 % lower in amplitude during rotor speed variations and 18 % higher in amplitude during blade pitch actuations

Coupling of Two Tools for the Simulation of Floating Wind Turbines

For the design of a floating wind turbine it is necessary to take the loading due to the wind, wave and current in equal consideration. The PHATAS computer program from ECN (Energy research Centre of the Netherlands) is a time-domain aero-elastic simulation program, that accounts for the complete mutual interaction of unsteady rotor aerodynamics, structural dynamics of the rotor blades and tower, and interaction with the turbine controller under influence of turbulent wind and wave loading for fixed wind turbines. The aNySIM computer program from MARIN is a multi rigid body time domain model that accounts for wave loadings, current loadings, wind loadings, floating body dynamics, mooring dynamics. The coupled computer program aNySIM / PHATAS accounts for all loadings acting on a floating wind turbine and its response whereas PHATAS can only be used for fixed wind turbines onshore and offshore. This paper reports on the dynamic coupling between PHATAS and aNySIM. As a typical case study, the controller for floating offshore wind turbines is evaluated. This new tool has been used to repeat phase IV of the Offshore Code Comparison Collaboration (OC3) within IEA Wind Task 23, regarding floating wind turbine modelling. The results of these simulations are presented in this paper

Closed Loop Control Strategies Definition v2

This report represents Deliverable D6.4 “Closed Loop Control Strategies Definition v2” of Work Package 6, “Integrity Management and Control Strategies”, of the EU H2020 project Mooring Sense. The purpose of this deliverable is to describe the closed-loop control strategies that have been designed and implemented within the project. Two control loops are proposed and integrated into IKERLAN’s OpenDiscon open-source wind turbine controller code. The first control loop implements a method from the literature introducing torque demand variations to reduce blade pitch oscillations around rated wind speed. The second control loop makes use of a thrust force observer and the feedback of the smart sensor designed for the MooringSense project (platform and turbine position and attitude) to limit the thrust force in the turbine. The mentioned observer description and validation is also provided in this document showing good correlation values between the estimated values and the values obtained from the simulation tools for different test cases. Similarly, the control algorithms are explained, and their performance is validated using the platform and turbine modelled in SIMA software. Finally, it is shown that both proposed strategies help to mitigate the loads in the mooring lines and the FOWT (tower, blades, etc.) in terms of magnitude and cyclic loading, increasing the fatigue life expectation. However, generator torque variations are increased for turbulent wind conditions and power production must be the reduced if the thrust limitation strategy is enabled

Monitoring, Digital Twin and Control Technologies for Mooring System Integrity Management in Floating Offshore Wind

<p>Efficient operation of mooring systems is of a major importance to reduce floating offshore wind energy costs. The MooringSense Project aims reduction of operational costs and increasing efficiency through the development of several enablers such as, a mooring system digital twin (DT), a smart motion sensor, a structural health monitoring system and control strategies at individual and farm levels.</p><p>The concept takes advantage of mooring systems' updated condition information, provided by a DT and innovative monitoring and control technologies, to allow the implementation of risk-based integrity management plans and more holistic control strategies. This Integrity Management Strategy intends to make a change from unscheduled corrective maintenance interventions to a scheduled predictive maintenance, which results in reduced costs of services and optimized availability.</p><p>The MooringSense concept involves the development of a set of technological tools that are currently under development.</p&gt