Comparative study of OMA applied to experimental and simulated data from an operating Vestas V27 wind turbine

Oscar Ramirez Requeson, Dmitri Tcherniak, Gunner Chr. Larsen

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Today, design of wind turbines is extensively done by the implementation of numerical models. These models simulate the dynamic behaviour of full-scale wind turbines which helps to ensure the structural integrity of prototypes. However, these numerical models need validation from experimental results, and in turn, numerical and analytical modelling help improve and validate new experimental techniques. Wind turbines are complex dynamic systems that consist of mutually moving substructures under high dynamic loads. At a standstill, the system can be modelled as linear time-invariant (LTI), and modal analysis requirements are thus fulfilled for the dynamic characterization. Under operation, the system cannot be considered as LTI and must be modelled as a linear periodic time-variant (LPTV) system, which allows for the application of the related theory for such systems. One of these methods is the Coleman transformation, which transforms the vibrations expressed in the blade rotating coordinates to the fixed-ground frame of reference. The application of this transformation, originally from helicopter theory, allows for the conversion of a LPTV system to a LTI system under certain assumptions, among which is the assumption of isotropic rotors. Since rotors are never completely isotropic in real life, this paper presents the application of operational modal analysis together with the Coleman transformation on both experimental data from a full-scale Vestas wind turbine with instrumented blades and nacelle, and its representative numerical model with a fully isotropic rotor. The results show that the first tower and rotor edgewise modes are well identified, and that the rotor edgewise modes can be identified from the nacelle signals. The results also uncover the challenge the excitation forces imply for the identification of flapwise modes.
Original languageEnglish
Title of host publicationProceedings of the 6th International Operational Modal Analysis Conference (IOMAC 2015)
Number of pages10
Publication date2015
Publication statusPublished - 2015
Event6th International Operational Modal Analysis Conference - Gijón, Spain
Duration: 12 May 201514 May 2015


Conference6th International Operational Modal Analysis Conference


  • Wind turbines
  • Structural dynamics
  • Operational modal analysis
  • Modal parameters
  • System Identification
  • Anisotropic rotors


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