Optical Measurements and Operational Modal Analysis on a Large Wind Turbine: Lessons Learned

Ozbek, Muammer; Rixen, Daniel J.

doi:10.1007/978-1-4419-9428-8_21

Cited by 23 publications

(10 citation statements)

References 23 publications

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“…Researchers [2][3][4][5] agree on the fact that performing modal analysis on a rotating turbine is much more challenging than performing the same analysis on a parked turbine due to the facts that;…”

Section: Analysis Results and Identified System Parametersmentioning

confidence: 99%

Aero-elastic Parameter Estimation of a 2.5 MW Wind Turbine Through Dynamic Analysis of In-Operation Vibration Data

Ozbek

Rixen

2014

Springer Proceedings in Physics

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Aero-elastic parameters of a 2.5 MW-80 m diameter-wind turbine were extracted by using the in-operation vibration data recorded for various wind speeds and operating conditions. The data acquired by 8 strain gauges (2 sensors on each blade and 2 sensors on the tower) installed on the turbine was analyzed by using OMA (Operational Modal Analysis) methods while several turbine parameters (eigenfrequencies and damping ratios) were extracted. The obtained system parameters were then qualitatively compared with the results presented in a study from literature, which includes both aeroelastic simulations and in-field measurements performed on a similar size and capacity wind turbine. IntroductionGrowing energy demands require wind turbine manufacturers to design more efficient and higher capacity wind turbines which inevitably results in larger and larger new models to be put into service. However, an important consequence of this increase in size and flexibility of the structure is the complicated dynamic interaction between different parts of the turbine. Motion of the blades interacts with aerodynamic forces, electro-magnetic forces in the generator and the structural dynamics of several turbine components (drive train, nacelle and tower). Understanding these dynamic interactions, the corresponding structural behavior

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Section: Analysis Results and Identified System Parametersmentioning

confidence: 99%

Aero-elastic Parameter Estimation of a 2.5 MW Wind Turbine Through Dynamic Analysis of In-Operation Vibration Data

Ozbek

Rixen

2014

Springer Proceedings in Physics

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“…These frequencies can be effective up to 24 P and sometimes coincide with the real eigenfrequencies of the system. Besides, for rotating turbines, these P harmonics cause violation of steady state random excitation assumption, which is one of the most important requirements of OMA algorithms. Another important assumption, time‐invariant system requirement, is also difficult to accomplish for rotating wind turbines because of the rotation of the blades and yawing, pitching motion of the turbine. However, for parked turbines, all these motions of the different components are prevented, which makes the time‐invariant system assumption much easier to fulfill.…”

Section: Analysis Results and Identified System Parametersmentioning

confidence: 99%

Operational modal analysis of a 2.5 MW wind turbine using optical measurement techniques and strain gauges

2012

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This work presents the results of in‐field tests performed on a 2.5 MW, 80 m diameter wind turbine. During the two test campaigns, dynamic response of the structure was monitored by using three different measurement systems, namely conventional strain gauges, photogrammetry and laser interferometry, whereas the turbine was both at parked condition and rotating. The recorded data were analysed by using an operational modal analysis algorithm based on the least square complex exponential method and several turbine parameters (eigenfrequencies and damping ratios) were extracted. The obtained system parameters were then qualitatively compared with the results presented in a study from literature, which includes both aeroelastic simulations and in‐field measurements performed on a similar size and capacity wind turbine. Copyright © 2012 John Wiley & Sons, Ltd.

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“…The stereo-photogrammetric measurement technique has been employed to measure large utility-scale wind turbine blades. Ozbeket al [18][19][20][21]applied the 3DPT to a 2.5-MW Nordex N80 wind turbine with an 80-meter tower height and rotor diameter. They also showed that modal parameters of the rotating utility-scale wind turbine blade can be identified using stereo-photogrammetric measurement.…”

Section: Prior Work Related To Photogrammetrymentioning

confidence: 99%

Large-area photogrammetry based testing of wind turbine blades

Poozesh

Baqersad

Niezrecki

et al. 2017

Mechanical Systems and Signal Processing

146

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An optically based sensing system that can measure the displacement and strain over essentially the entire area of a utility-scale blade leads to a measurement system that can significantly reduce the time and cost associated with traditional instrumentation. This paper evaluates the performance of conventional three dimensional digital image correlation (3D DIC) and three dimensional point tracking (3DPT) approaches over the surface of wind turbine blades and proposes a multi-camera measurement system using dynamic spatial data stitching. The potential advantages for the proposed approach include: (1) full-field measurement distributed over a very large area, (2) the elimination of timeconsuming wiring and expensive sensors, and (3) the need for large-channel data acquisition systems. There are several challenges associated with extending the capability of a standard 3D DIC system to measure entire surface of utility scale blades to extract distributed strain, deflection, and modal parameters. This paper only tries to address some of the difficulties including: (1) assessing the accuracy of the 3D DIC system to measure full-field distributed strain and displacement over the large area, (2) understanding the geometrical constraints associated with a wind turbine testing facility (e.g. lighting, working distance, and speckle pattern size), (3) evaluating the performance of the dynamic stitching method to combine two different fields of view by extracting modal parameters from aligned point clouds, and (4) determining the feasibility of employing an output-only system identification to estimate modal parameters of a utility scale wind turbine blade from optically measured data. Within the current work, the results of an optical measurement (one stereo-vision system) performed on a large area over a 50-meter utility-scale blade subjected to quasistatic and cyclic loading are presented. The blade certification and testing is typically performed using International Electro-Technical Commission standard (IEC 61400-23). For static tests, the blade is pulled in either flap-wise or edgewise directions to measure deflection or distributed strain at a few limited locations of a large-sized blade. Additionally, the paper explores the error associated with using a multi-camera system (two stereo-vision systems) in measuring 3D displacement and extracting structural dynamic parameters on a mock set up emulating a utility-scale wind turbine blade. The results obtained in this paper reveal that the multi-camera measurement system has the potential to identify the dynamic characteristics of a very large structure.

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Optical Measurements and Operational Modal Analysis on a Large Wind Turbine: Lessons Learned

Cited by 23 publications

References 23 publications

Aero-elastic Parameter Estimation of a 2.5 MW Wind Turbine Through Dynamic Analysis of In-Operation Vibration Data

Aero-elastic Parameter Estimation of a 2.5 MW Wind Turbine Through Dynamic Analysis of In-Operation Vibration Data

Operational modal analysis of a 2.5 MW wind turbine using optical measurement techniques and strain gauges

Large-area photogrammetry based testing of wind turbine blades

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