bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predicting the benefit of wake steering on the annual energy production of a wind farm using large eddy simulations and Gaussian process regression
Authors: Hoek Daan van der , Doekemeijer Bart , Andersson Leif Erik , Wingerden Jan-Willem van 
Published: September 2020

Abstract
In recent years, wake steering has been established as a promising method to increase the energy yield of a wind farm. Current practice in estimating the benefit of wake steering on the annual energy production (AEP) consists of evaluating the wind farm with simplified surrogate models, casting a large uncertainty on the estimated benefit. This paper presents a framework for determining the benefit of wake steering on the AEP, incorporating simulation results from a surrogate model and large eddy simulations in order to reduce the uncertainty. Furthermore, a time-varying wind direction is considered for a better representation of the ambient conditions at the real wind farm site. Gaussian process regression is used to combine the two data sets into a single improved model of the energy gain. This model estimates a 0.60% gain in AEP for the considered wind farm, which is a 76% increase compared to the estimate of the surrogate model.
Torque measurements from MW wind turbine Gearboxes: a system identification approach
Authors: Santiago U Gutierrez , van Wingerden J W , Polinder H , Sisón A Fernández 
Published: September 2020

Abstract
The gearbox is a critical component of modern MW wind turbines. An accurate model of the gearbox dynamics is needed to improve gearbox design, develop advanced control algorithms, and more effective fault diagnosis tools which could lead to lower the cost of energy from wind. The objective of this paper is to investigate how torque measurements can be used in a data-driven framework to build dynamic models of wind turbine gearboxes.
An initial torsional model has been derived from first principles considering the stiffness of the gears, shafts, and structural components in the gearbox together with the mechanical components of the test bench. This model has been used to create simulated data of the experiments performed on gearboxes and to apply system identification techniques to the simulated signals, with a focus on predictor based subspace identification methods. System identification has been applied to torque and speed data measured on physical tests of two 3.4MW gearboxes. Gearbox excitation frequencies and their harmonics dominate the measured signals and disturb the system identification algorithms. Several techniques have been investigated to remove the shaft rotation and gear mesh frequency harmonics of the torque and rotational speed signals based on time synchronous averaging.
Overview of FLORIS updates
Authors: Fleming Paul , King Jennifer , Bay Christopher J. , Simley Eric , Mudafort Rafael , Hamilton Nicholas , Farrell Alayna , Martinez-Tossas Luis 
Published: September 2020

Abstract
In this paper, we review updates made to the FLORIS (FLOw Redirection and Induction in Steady State) open-source framework for wind farm control modeling, design and analysis. The updates are focused on improvements for large arrays of turbines - including heterogenous inflows and incorporating second-order wake steering effects - design, and analysis tools for practical application of wind farm control, and improvements to the software architecture for best practices in modularization and cooperative development.
Real-time identification of clusters of turbines
Authors: Bernardoni Federico , Ciri Umberto , Rotea Mario , Leonardi Stefano 
Published: September 2020

Abstract
The implementation of wind farm control strategies requires knowledge of the turbines that are aerodynamically coupled through wake effects. As the wind changes direction, the clusters of coupled turbines may vary within the array. The present study proposes a simple method to identify clusters of turbines coupled by the wake interaction. The method uses the correlation of the power production fluctuations of the turbines in the wind farm. Large Eddy Simulations (LES) results of the flow in a 4×4 turbine array have been used to validate the proposed approach. This study introduces a tool which can be integrated into a control system to optimize wind plant power production.
Effects of dynamic induction control on power and loads, by LES-ALM simulations and wind tunnel experiments
Authors: Wang C , Campagnolo F , Sharma A , Bottasso C L 
Published: September 2020

Abstract
Dynamic Induction Control (DIC) has the potential of boosting wind farm power by enhancing wake recovery, whereby periodic pitch motions are used to exploit the natural instabilities of wind turbine wakes. This work studies DIC both experimentally and numerically. A thorough validation of an LES-ALM (Actuator Line Method) simulation tool is first conducted against experimental measurements. This shows that the CFD model is able to accurately simulate the power, loads and wake behavior of a wind turbine operating with DIC. The validated CFD model is then employed to study the effects of some DIC parameters. Results indicate an increase in the fatigue loads caused by the pitch activity that enhances wake recovery.
Launch of the FarmConners Wind Farm Control benchmark for code comparison
Authors: Göçmen Tuhfe , Kölle Konstanze , Andersen Søren Juhl , Eguinoa Irene , Duc Thomas , Campagnolo Filippo , Iribas-Latour Mikel , Astrain David , Bottasso Carlo , Meyers Johan , van Wingerden Jan Willem , Giebel Gregor 
Published: September 2020

Abstract
Careful validation of the modelling and control actions is of vital importance to build confidence in the value of coordinated wind farm control (WFC). The efficiency of flow models applied to WFC should be evaluated to provide reliable assessment of the performance of WFC. In order to achieve that, FarmConners launches a common benchmark for code comparison to demonstrate the potential benefits of WFC, such as increased power production and mitigation of loads. The benchmark builds on available data sets from previous and ongoing campaigns: synthetic data from high-fidelity simulations, measurements from wind tunnel experiments, and field data from a real wind farm. The participating WFC models are first to be calibrated or trained using normal operation periods. For the blind test, both the axial induction and wake steering control approaches are included in the dataset and to be evaluated through the designed test cases. Three main test cases are specified, addressing the impact of WFC on single full wake, single partial wake, and multiple wake. The WFC model outcomes will be compared during the blind test phase, through power gain and wake loss reduction as well as alleviation of wake-added turbulence intensity and structural loads. The probabilistic validation will be based on the median and quartiles of the observations and WFC model predictions. Every benchmark participant will be involved in the final publication, where the comparison of different tools will be performed using the defined test cases. Instructions on how to participate are also provided on farmconners.readthedocs.io.
Fault detection of wind turbine gearbox using thermal network modelling and SCADA data
Authors: Corley B. , Carroll J. , Mcdonald A. 
Published: September 2020

Abstract
This work uses a detailed understanding of the physics inside a wind turbine gearbox and SCADA temperature data as an alternative to data-driven techniques for fault detection. Thermal modelling based on the principles of heat transfer theory is used with the aim of understanding the thermal behaviour of a ‘healthy’ gearbox and use it to detect abnormal gearbox operating conditions. Data for turbines, ‘healthy’ and one month to fail, are analysed for two different failure modes to see if a fault can be detected in advance with the aim to improve physical understanding of wind turbine gearbox operation and condition monitoring techniques.
Effects of induction and wake steering control on power and drivetrain responses for 10 MW floating wind turbines in a wind farm
Authors: Binsbergen Dirk Willem van , Wang Shuaishuai , Nejad Amir R. 
Published: September 2020

Abstract
This paper aims to investigate the drivetrain load response caused by induction and wake steering control on two floating wind turbines (FWTs) in a wind farm. In this study, two DTU 10 MW turbines, supported on the nautilus floater, are modelled using FAST.Farm. The downstream turbine is placed at the distance of seven rotor diameters (D) from the upstream turbine in the positive wind direction. Partial wake shading is considered for wake steering control and full wake shading is considered for induction control. An ambient wind speed of 8m/s is used and a representative sea state is selected. The test cases are defined based on different blade pitch and yaw angles of the upstream turbine. Power generation of the offshore wind farm is studied under different test cases. A decouped analysis approach is used to investigate drivetrain response. Global responses are obtained from FAST.Farm. These loads are used as input of the 10 MW wind turbine drivetrain model for the gears and bearings load response analysis. Results show that both induction and wake steering control lead to a limited increase in power generation of the wind farm. Additionally, both control methods affect the drivetrain response statistics, while the features are different. This study facilitates a better understanding on drivetrain dynamic behaviour in a wind farm perspective, which serves as a reference for the wind farm optimizaton in the future.
On wind farm wake mixing strategies using dynamic individual pitch control
Authors: Frederik Joeri , Doekemeijer Bart , Mulders Sebastiaan , van Wingerden Jan-Willem 
Published: September 2020

Abstract
Dynamic wind farm control is a new strategy that aims to apply time-varying, often periodic, control signals on upstream wind turbines to increase the wake mixing behind the turbine. As a result, wake recovery is accelerated, leading to a higher power production of downstream turbines. As the amount of interest in dynamic control strategies for wind turbines in a wind farm is increasing, different approaches are being proposed. One such novel approach is called Dynamic Individual Pitch Control (DIPC). In DIPC, each blade pitch angle of a turbine is controlled independently to dynamically manipulate the direction of the thrust force vector exerted on the wind. Hence, the direction of the wake is varied, inducing wake mixing without significant thrust force magnitude variations on the rotor. In this paper, the effectiveness of different variations in the thrust direction are evaluated and compared using Large Eddy Simulation (LES) experiments.
Model approach for electromagnetically excited mechanical vibrations in direct-drive wind turbines
Authors: Mülder Christoph , Duda Tobias , Jacobs Georg , Hameyer Kay 
Published: September 2020

Abstract
In this paper a multi-physical modelling approach for calculating parasitic magnetic force excitations in wind turbine generators is presented. These parasitic excitations are dependent on the magnetic field distribution in the air gap and the air gap geometric shape, which is dependent on the external loads of the wind turbine. With this methodology mechanical multibody simulation is coupled with electromagnetic field calculation by means of finite-element calculation. First the general methodology and the calculation of the air gap width distribution is presented and subsequently the electromagnetic field and force calculation is explained.
Lightweight optimal rotor design of a 10MW-scale wind turbine using passive load control methods
Authors: Serafeim Giannis P. , Manolas Dimitris I. , Riziotis Vasilis A. , Chaviaropoulos Panagiotis K. 
Published: September 2020

Abstract
The present paper investigates the potential to reduce the mass of the blade of the 10MW DTU Reference Wind Turbine through build-in, material bend-twist coupling (BTC). It is materialized by introducing an offset angle on the plies of the uni-directional material over the spar caps of the blade. Optimum BTC designs are obtained on the basis of an integrated optimization framework combining an aeroelastic solver for the calculation of the structural loads of the blade and a cross-sectional tool that provides beam-like structural properties of the blade and stresses distributions. The derived designs are verified based on a subset of representative fatigue and ultimate design loads cases of IEC 61400-1. Reduction of the combined bending moment at the root of the blade by 5% and reduction of the blade mass by 10% is achieved with a hybrid model consisting of three span-wise segments having different constant ply offset angles.
A control cost criterion for controller tuning of two- and three-bladed 20 MW offshore wind turbines
Authors: Anstock Fabian , Schorbach Vera 
Published: September 2020

Abstract
When wind turbine concepts are modified, the difference in characteristic behavior and the impact on the cost of energy are of great interest. However, before comparing it is mandatory to re-adapt controller gains or weights to altered turbine dynamics in order to guarantee a still suitable overall system design. As an expenditure-based solution, the proposed control cost criterion could help to assess changes of turbine concepts better due to a clear and objective controller tuning. Conflicting design objectives are therefore assessed on their approximated influence on the cost of energy in order to result in the most cost-beneficial trade-off. These objectives are variations of component loads, actuator usage, and energy production. The criterion is applied to three- and two-bladed 20 MW offshore turbines with turbulent wind for full load operation, exemplarily. This provides insight into the benefits and limitations of low controller integral pitch gains and results in potential cost reductions for all turbines.
Development of a digital twin of an onshore wind turbine using monitoring data
Authors: Pimenta F , Pacheco J , Branco C M , Teixeira C M , Magalhães F 
Published: September 2020

Abstract
The present paper has two main objectives: (1) to create a digital twin of an onshore wind turbine to provide to the owner of the wind farm a tool for continuous tracking of accumulated fatigue damage and evaluation of alternative operation strategies; (2) to perform the first tasks for the creation a reliable numerical of a floating wind turbine to simulate experimental data for the testing of monitoring tools on this type of wind turbines. A numerical model of an onshore wind turbine was created with FAST software developed by the US National Renewable Energy Laboratory (NREL). The structural and mechanical properties of the structure were calculated from the geometric properties of the tower and blades. The aerodynamic properties of different sections of the blades were computed with 2D models created with ANSYS Fluent. Having the wind turbine fully characterised, the control mechanisms were calibrated using data from the manufacturer catalogues. Numerous time series of wind excitation for different operation conditions were generated, and the structural response computed. Additionally, the Supervisory Control and Data Acquisition (SCADA) operating in parallel with a series of extensometers and accelerometers located in strategic points along a real wind turbine tower and blades provided a full description of the internal forces in both locations and the estimation of the modal properties for different operating conditions. Both measured and simulated response allowed the identification and validation of structural dynamic properties and static and dynamic internal loads. In spite of several approximations and simplifications, the results obtained with the numerical model were in good agreement with the ones measured in the field.
Loop shaping based robust control for floating offshore wind turbines
Authors: Yu Wei , Lemmer Frank , Schlipf David , Cheng Po Wen 
Published: September 2020

Abstract
In this work, a thorough and complete methodology for the widely used SISO controller is described for floating offshore wind turbines (FOWTs). The motivation is to develop clear, easy implementable and automated design criteria of blade pitch control design, which takes both stability and performance into account for FOWTs without adding new sensors. The primary design criteria is to achieve a similar dynamic step response behaviour, i.e. overshooting, rise time and settling time across the operating points above rated wind speeds. The proposed design procedure can be performed by lower order numerical models with only two degrees of freedom, which can be derived analytically. The minimal required system information eases an early stage controller design, as well as the system engineering and integrated substructure design. The proposed design procedure is evaluated on three state of the art floating wind turbines. The resulting gain scheduling is quite different from the one for onshore turbines. The overall response is satisfying and comparable with an existing stability-oriented robust SISO controller at operation points where stability is critical. An improved performance is found for higher wind speeds.
Modal Analysis of a Quad-Rotor Wind Turbine
Authors: Ferede Etana , Gandhi Farhan 
Published: September 2020

Abstract
Unlike Single-Rotor wind turbines, stability analysis of Multi-Rotor wind turbines is still in its initial stages. This paper presents the modal analysis of a Quad-Rotor wind turbine and identifies the new modes or possible instability modes that are otherwise not present on a Single-Rotor wind turbine. Multi-Blade Coordinate transformation scheme is adapted to a Quad-Rotor wind turbine to write the system’s equation of motion in fixed-reference frame followed by Eigenvalue analysis to determine the natural frequencies and mode shapes of the Quad-Rotor wind turbine. A Campbell diagram of the Quad-Rotor wind turbine is presented. Results indicate that the Quad-Rotor turbine is soft-soft to the first tower modes (fore-aft, side-side, and torsion). Furthermore, the modes with low natural frequency other than the tower modes are a combination of tower, boom, and blade modes. Therefore, due to the presence of blade modes, the modal frequency of these modes increases or decreases with increasing rotor speed due to centrifugal stiffening.
Validation of the quasi-steady performance model for pumping airborne wind energy systems
Authors: Schelbergen Mark , Schmehl Roland 
Published: September 2020

Abstract
The quasi-steady performance model (QSM) has been developed specifically for pumping airborne wind energy systems using flexible membrane wings. In this study, we validate this model using a comprehensive set of flight data that includes 87 consecutive pumping cycles and is acquired with the development platform of Kitepower B.V. The aerodynamic properties of the kite are determined using onboard measurements of the relative flow velocity. We found that neglecting the vertical wind component and straightening and slacking motion of the tether lead to substantial errors in the kite velocity calculated using the system model. A reasonable agreement between the QSM simulations and flight data can be obtained by multiplying the kite’s drag coefficient by a fudge factor and thereby turning the QSM into a grey-box model. The model accuracy is statistically evaluated as opposed to only evaluating a single pumping cycle per system configuration as done in earlier research.
Energy harvesting via co-locating horizontal- and vertical-axis wind turbines
Authors: Hansen M. , Enevoldsen P. , Abkar M. 
Published: September 2020

Abstract
Co-locating horizontal- and vertical-axis wind turbines has been recently proposed as a possible approach to enhance the land-area power density of wind farms. In this work, we aim to study the benefits associated with such a co-location using large-eddy simulation (LES) and analytical wake models. In this regard, small-scale vertical-axis wind turbines (VAWTs) in triangular clusters are deployed within a finite-size wind farm consisting of horizontal-axis wind turbines (HAWTs). Wake flow within the wind farm and the effect of VAWTs on the overall wind-farm efficiency are investigated and quantified. The results show that the optimal deployment of small-scale VAWTs has a negligible impact on the performance of HAWT arrays while increasing the total power production. For the particular cases considered here, the power output of the co-located wind farm increases up to 21% compared to the baseline case in which only the HAWTs are present. Also, by comparing to the LES results, it is shown that the analytical framework proposed here is able to accurately predict the power production of wind farms including both HAWTs and VAWTs. Finally, as a real-world application, potential benefits of deploying small-scale VAWTs inside the Horns Rev 1 wind farm are explored for various wind directions using the calibrated wake model. The results show potential for about an 18% increase in the wind-farm power production, averaged over all wind directions, for a particular VAWT layout investigated in this study. The levelized cost of energy (LCoE) for the co-located wind farm is also assessed. The simulations finds that meanwhile the installation of VAWTs increases the annual energy production (AEP) of the wind farm, it also increases the LCoE, which is caused by a) lack of operational data, and b) a low TRL (Technology Readiness Levels) for VAWTs and floating foundations.
Reynolds-averaged Navier-Stokes simulations of the flow past a leading edge inflatable wing for airborne wind energy applications
Authors: Viré Axelle , Demkowicz Patryk , Folkersma Mikko , Roullier Arthur , Schmehl Roland 
Published: September 2020

Abstract
In this work we present Reynolds-averaged Navier-Stokes (RANS) simulations of the flow past the constant design shape of a leading-edge inflatable (LEI) wing. The simulations are performed with a steady-state solver using a k − ω SST turbulence model, covering a range of Reynolds numbers between 105 ≤ and ≤ 15 × 106 and angles of attack varying between −5° and 24°, which are representative for operating conditions in airborne wind energy applications. The resulting force distributions are used to characterize the aerodynamic performance of the wing. We found that a γ −

R
¯

e
θ

transition model is required to accurately predict the occurrence of stall up to at least Re= 3 × 106. The work highlights similarities with the flow past a two-dimensional LEI airfoil, in particular, with respect to flow transition and its influence on the aerodynamic properties. The computed values of the lift and drag coefficients agree well with in-flight measurements acquired during the traction phase of the LEI wing operation. The simulations show that the three-dimensional flow field exhibits a significant cross flow along the span of the wing.
Scaling of Experimental Buoyancy Vortex Structures with Respect to Power Generation
Authors: Hawkes N.A. , Flay R.G.J. , Cater J.E. , Macdonald M. 
Published: September 2020

Abstract
A scaling or nondimensionalisation of atmospheric buoyancy vortices for power generation (based on the Oberbeck-Boussinesq assumption) is proposed that uses a published formulation from the study of Rotating Rayleigh-Benard Convection. This is combined with assumptions that the vortex flows are pseudo-cyclostrophic and that a radial Richardson number can serve as a predictor of the onset of Kelvin-Helmholtz instability leading to a transition to a turbulent plume, in order to locate the cold reservoir of the vortex when viewed as a heat engine. This permits the prediction of the behaviour of large vortices in atmosphere using data from experiments on small vortices.