Full-scale modal wind turbine tests: comparing shaker excitation with wind excitation

Osgood, Richard M.; Bir, Gunjit; Mutha, Heena K; Peeters, Bart; Łuczak, Marcin; Sablon, Gert

doi:10.1007/978-1-4419-9716-6_11

Cited by 30 publications

(22 citation statements)

References 12 publications

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“…The linearized plant model is derived from the FAST non-linear model of the CART3 [17]. The original non-linear model was developed using knowledge of the turbine, then tuned to match the results of modal testing [18]. The linear model includes several degrees of freedom including: generator speed, drivetrain torsion, tower side-side bending and the derivatives.…”

Section: A Turbine Modelmentioning

confidence: 99%

Field testing a wind turbine drivetrain/tower damper using advanced design and validation techniques

Fleming

Wingerden

Scholbrock

et al. 2013

2013 American Control Conference

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As an ongoing trend, the design of wind turbines is moving towards larger machines with components optimized for cost effectiveness. This leads to very large and flexible structures with lightly damped modes. Good control design is becoming more essential to ensure safe and stable operation over the life of the turbine. Additionally, there is growing interest in expanding the number of sensors and actuators available for closed-loop control. The increasing number of control variables in modern wind turbines will necessitate model-based controller design to handle the complexity of the flexible and coupled control loops in an effective and robust way.Recent literature in wind energy has explored the use of modern control design techniques such as state-space and robust control design methods and closed-loop system identification for model identification. However, this literature is, to date, mostly confined to simulation studies. Field testing is necessary to demonstrate the effectiveness of advanced design and validation techniques in a practical application. In this paper, we design two alternative dampers for the lightly damped drivetrain and tower modes of an experimental turbine. One design is based on classical iterative design approaches, while the other uses an H ∞ approach. The two controllers are then validated using two alternative methods: the traditional extended field test and a relatively short system identification experiment. The paper demonstrates that even in this sub-problem of wind turbine control consisting of only two loops, the use of advanced design and validation techniques is very effective at converging quickly to good control designs and quickly assessing their performance.

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Section: A Turbine Modelmentioning

confidence: 99%

Field testing a wind turbine drivetrain/tower damper using advanced design and validation techniques

Fleming

Wingerden

Scholbrock

et al. 2013

2013 American Control Conference

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“…10 A FAST model of the CART3 was developed, using known structural properties, and tuned to match the results of a modal test completed in 2009. 11 This non-linear model was then linearized at a range of wind-speeds to produce a set of mode frequencies and mode damping for modes in the range of 0-10 Hz. In Figure 8, the result of this simulation is shown.…”

Section: Iva2 Whirl and Flapwise Couplingmentioning

confidence: 99%

Resonant Vibrations Resulting from the Re-Engineering of a Constant-Speed 2-Bladed Turbine to a Variable-Speed 3-Bladed Turbine

Fleming

Wright

Fingersh

et al. 2011

49th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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The CART3 (Controls Advanced Research Turbine, at the National Wind Technology Center has recently been converted from a 2-bladed constant speed machine to a 3-bladed variable speed machine designed specifically for controls research. The purpose of this conversion was to develop an advanced controls field-testing platform which has the more typical 3-bladed configuration. A result of this conversion was the emergence of several resonant vibrations, some of which initially prevented operation of the turbine until they could be explained and resolved. In this paper, the investigations into these vibrations are presented as "lessons-learned". Additionally, a frequency-domain technique called waterfall plotting is discussed and its usefulness in this research is illustrated.

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“…The sensor placement strategy during the blade measurements is partly based on Larsen et al, where an LM 19 blade (length 19 m) and CMA techniques were used. Another test setup for blade measurements using OMA techniques on a 600‐kW test wind turbine has been described by Osgood et al As an alternative to acceleration recordings, the deformation of a blade can be directly measured by large‐area photogrammetry which has been applied to a wind turbine blade on test rig by Poozesh et al …”

Section: Introductionmentioning

confidence: 99%

Experimental identification of modal parameters of an industrial 2‐MW wind turbine

Zierath¹,

Rachholz

Rosenow³

et al. 2018

Wind Energy

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This contribution presents modal testing of a 2-MW wind turbine on a 100-m tubular tower with a 93-m rotor developed by W2E Wind to Energy GmbH. This research is part of the DYNAWIND project of the University of Rostock and W2E. Beside classical modal analysis schemes, this contribution mainly focusses on the application of operational modal analysis techniques to a wind turbine. Specific problems are addressed, and hints for modal testing on wind turbines are given. Furthermore, an effective measurement setup is proposed for identification of the modal parameters of a wind turbine. The measurement campaign is divided in two parts. First, a measurement campaign using 8 sensor positions on a rotor blade was done while the rotor is lying on ground. Second, a detailed measurement campaign was done on the entire wind turbine with the rotor locked in Y position using 61 sensor positions on the tower, the mainframe, the gearbox, the generator, and the low-voltage unit. While the rotor blade was tested by classical and operational modal analysis techniques, the entire wind turbine was tested by operational modal analysis techniques only. The mode shapes and eigenfrequencies of the wind turbine identified within the measurement campaigns are within the expected range of the design values of the wind turbine. But in contrast, the damping ratios differ strongly from those given in guidelines and literature. Furthermore, a strong influence of aerodynamic damping compared to structural damping is observed for the first tower mode even for a parked wind turbine. KEYWORDS modal testing, operational modal analysis, 2-MW wind turbine INTRODUCTIONThe life cycle of a wind turbine is mainly influenced by its dynamics. To avoid resonances in the variable speed range of a wind turbine, resonant frequencies of the entire turbine including substructure resonant frequencies as well as harmonic excitations must be known accurately. Whereas the harmonic excitation frequencies are multiples of the rotational speed and well known, resonant frequencies have to be calculated using a proper simulation model or identified experimentally. A verification of calculated results by measurements is the preferable approach. So the extensive knowledge and the deep understanding of the dynamics of a wind turbine allows precise prediction of its behaviour. For the identification of the modal parameters the classical modal analysis (CMA) and the operational modal analysis (OMA) are chosen.The lowest resonant frequencies of the entire turbine and corresponding mode shapes, affected mainly by tower and blades, have to be considered with respect to the first and third-order excitations (rotational frequency and blade passing frequency, respectively) to avoid severe resonance problems during operation. Resonant frequencies of the main frame have to be considered with respect to higher excitation orders resulting mainly from the rotational frequency of the generator. Dynamic deflections of the main frame, potentially inducing undesirable loads on the drive tra...

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Full-scale modal wind turbine tests: comparing shaker excitation with wind excitation

Cited by 30 publications

References 12 publications

Field testing a wind turbine drivetrain/tower damper using advanced design and validation techniques

Field testing a wind turbine drivetrain/tower damper using advanced design and validation techniques

Resonant Vibrations Resulting from the Re-Engineering of a Constant-Speed 2-Bladed Turbine to a Variable-Speed 3-Bladed Turbine

Experimental identification of modal parameters of an industrial 2‐MW wind turbine

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