Preprints
https://doi.org/10.5194/wes-2021-41
https://doi.org/10.5194/wes-2021-41

  12 Jul 2021

12 Jul 2021

Review status: this preprint is currently under review for the journal WES.

Damping Identification of Offshore Wind Turbines using Operational Modal Analysis: A Review

Mees van Vondelen1, Sachin T. Navalkar2, Alexandros Iliopoulos2, Daan van der Hoek1, and Jan-Willem van Wingerden1 Mees van Vondelen et al.
  • 1Delft Center for Systems and Control, Delft University of Technology, 2628CN Delft, the Netherlands
  • 2Siemens Gamesa Renewable Energy, Prinses Beatrixlaan 800, 2595BN Den Haag, the Netherlands

Abstract. To increase the contribution of offshore wind energy to the global energy mix in an economically sustainable manner, it is required to reduce the costs associated with the production and operation of offshore wind turbines (OWTs). One of the largest uncertainties and sources of design conservatism for OWTs is the determination of the global damping level of the OWT. Estimation of OWT damping based on field measurement data has hence been subject to considerable research attention and is based on the use of (preferably operational) vibration data obtained from sensors mounted on the structure. As such, it is an output-only problem and can be addressed using state-of-the-art Operational Modal Analysis (OMA) techniques, reviewed in this paper. The evolution of classical time- and frequency-domain OMA techniques has been reviewed; however, literature shows that the OWT vibration data is often contaminated by rotor speed harmonics of significantly high energy located close to structural modes, which impede classical damping identification. Recent advances in OMA algorithms for known or unknown harmonic frequencies can be used to improve identification in such cases. Further, the transmissibility family of OMA algorithms is purported to be insensitive to harmonics. Based on this review, a classification of OMA algorithms is made according to a set of novel suitability criteria, such that the OMA technique appropriate to the specific OWT vibration measurement setup may be selected. Finally, based on this literature review, it has been identified that the most attractive future path for OWT damping estimation lies in the combination of uncertain non-stationary harmonic frequency measurements with statistical harmonic isolation to enhance classical OMA techniques, orthogonal removal of harmonics from measured vibration signals, and in the robustification of transmissibility-based techniques.

Mees van Vondelen et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wes-2021-41', Anonymous Referee #1, 04 Oct 2021
  • RC2: 'Comment on wes-2021-41', Anonymous Referee #2, 06 Oct 2021

Mees van Vondelen et al.

Mees van Vondelen et al.

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Short summary
The damping of an offshore wind turbine is a difficult physical quantity to predict, although it plays a major role in a cost-effective turbine design. This paper presents a review of all approaches that can be used for damping estimation directly from operational wind turbine data. As each use case is different, a novel suitability table is presented to enable the user to choose the most appropriate approach for the given availability and characteristics of measurement data.