An investigation on wind turbine resonant vibrations

Tibaldi, Carlo; Kim, Taeseong; Larsen, Torben J.; Rasmussen, Flemming; Serra, Richard; Sanz, Fredy A.

doi:10.1002/we.1869

Cited by 19 publications

(12 citation statements)

References 23 publications

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“…Dynamic deflections of the main frame, potentially inducing undesirable loads on the drive train, have to be minimized. Resonance phenomena have a large impact on the loads and power efficiency of a wind turbine, see previous studies …”

Section: Introductionmentioning

confidence: 94%

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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Section: Introductionmentioning

confidence: 94%

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

Zierath¹,

Rachholz

Rosenow³

et al. 2018

Wind Energy

View full text Add to dashboard Cite

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“…Dimensioning of the monopiles is usually dictated by the fatigue loads, caused by wind and waves exciting primarily a combination of the two lowest tower modes, the fore‐aft mode in the rotor direction and the side‐side mode lateral to the rotor direction. Waves acting with an angle to the wind can therefore cause large fatigue damage because of the absence of the aerodynamic damping in the direction lateral to the wind . The future will see an increasing number of larger and more slender wind turbines positioned at deeper water depths .…”

Section: Introductionmentioning

confidence: 99%

“…Waves acting with an angle to the wind can therefore cause large fatigue damage because of the absence of the aerodynamic damping in the direction lateral to the wind. [1][2][3] The future will see an increasing number of larger and more slender wind turbines positioned at deeper water depths. 4 For these structures, the natural frequencies of the critical tower modes will be lower than for present day wind turbine structures, which will cause fatigue damage because of resonant wave loading to increase significantly.…”

Section: Introductionmentioning

confidence: 99%

Active tuned mass damper for damping of offshore wind turbine vibrations

2016

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An active tuned mass damper (ATMD) is employed for damping of tower vibrations of fixed offshore wind turbines, where the additional actuator force is controlled using feedback from the tower displacement and the relative velocity of the damper mass. An optimum tuning procedure equivalent to the tuning procedure of the passive tuned mass damper combined with a simple procedure for minimizing the control force is employed for determination of optimum damper parameters and feedback gain values. By time domain simulations conducted in an aeroelastic code, it is demonstrated that the ATMD can be used to further reduce the structural response of the wind turbine compared with the passive tuned mass damper and this without an increase in damper mass. A limiting factor of the design of the ATMD is the displacement of the damper mass, which for the ATMD, increases to compensate for the reduction in mass. Copyright © 2016 John Wiley & Sons, Ltd.

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“…A comprehensive review of some trailing‐edge noise prediction models may be found in the work of Kamruzzaman et al On the other hand, outdoor noise emissions from isolated wind turbines and farms have been predicted from propagation models based on ray tracing that simulates the ground and air effects . In addition, the effect of resonant conditions in modern large‐scale wind turbines has recently been studied by Tibaldi et al , who reported that aeroelastic modes might be excited, depending upon the wind turbine operational external excitations.…”

Section: Introductionmentioning

confidence: 99%

Indoor simulation of amplitude modulated wind turbine noise

2016

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Wind energy is the world's fastest-growing renewable energy source; as a result, the number of people exposed to wind farm noise is increasing. Because of its broadband amplitude-modulated characteristic, wind turbine noise (WTN) is more annoying than noise produced by other common community/industrial sources. As higher frequencies are attenuated by air absorption and building transmission, the noise from modern large wind farms is mainly below 1000 and 500 Hz for outdoor and indoor conditions, respectively. Many WTN complaints relate to indoor, nighttime conditions when background noise levels are lower. As recently reported, indoor noise has the potential to cause sleeping disorders. Studies on human response to amplitude modulated WTN have been mainly focused on the outdoors, where a large amount of measured data exists. This is not the case for indoors, where it is much harder to gather data. Hence, there is a need to understand the transmission of WTN into dwellings and to develop indoor annoyance metrics. In this article, we investigate the transmission of WTN into residential-type structures. Using an outdoor WTN recording and structures with different properties/ configurations, we made a series of computer simulations for indoor noise predictions and assessed the results employing several widely used metrics for WTN, for example, spectral content, modulation depth and overall levels. In general, the indoor noise levels are higher, and the average modulation depth is similar to those of outdoor recordings. In addition, there is a significant change in the spectral shape. These results could potentially explain indoor WTN annoyance. 507predicted from propagation models based on ray tracing that simulates the ground and air effects. 7 In addition, the effect of resonant conditions in modern large-scale wind turbines has recently been studied by Tibaldi et al., 8 who reported that aeroelastic modes might be excited, depending upon the wind turbine operational external excitations.Broadband aerodynamic blade noise is responsible for the amplitude modulation (AM) observed mainly in large turbines, that is, a pulsating broadband sound. 2,3,9 This AM, commonly referred to as 'swishing', 'whooshing' or 'pulsating' noise, is currently considered to be the main cause of annoyance for residents living near wind farms. 10,11 Recently, infrasound from wind turbines has also received significant attention. 11,12 However, the generation of this noise component is not well understood and cannot easily be quantified, since a limited number of conclusive measurements are available.Turbines are not typically as loud as other sources of industrial or transportation noise at a similar distance. The AM characteristic is what makes WTN more annoying than other types of noises at the same sound pressure level (SPL). Very quiet rural communities that lack the masking of nighttime traffic noise are particularly affected. AM noise is perceived as more annoying than a constant amplitude sound containing the same spectrum and averag...

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An investigation on wind turbine resonant vibrations

Cited by 19 publications

References 23 publications

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

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

Active tuned mass damper for damping of offshore wind turbine vibrations

Indoor simulation of amplitude modulated wind turbine noise

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