Abstract
Noise, vibration and harshness (NVH) problems are critical issues to be tackled for wind turbine drivetrains. Tracking the behavior of modal parameters of the machines’ fundamental modes during operation it is of high interest to validate complex simulation models. A powerful approach for this purpose is represented by operational modal analysis (OMA). This paper describes the investigation of an automated technique for continuously tracking the modes of a rotating mechanical system running in normal operating conditions. The modal estimation procedure is based on an automatic version of the pLSCF (poly-reference Least-Square Complex Frequency-Domain) algorithm. The latter is coupled with a method that automatically tracks the modal parameters along different data sets. The use of OMA on a rotating component of the wind turbine creates the need to deal with harmonics in order to satisfy one of the assumptions of OMA. For this purpose, the use of a cepstrum editing procedure is analyzed and implemented. Modal estimates obtained from an automated analysis on stand still data and normal operating conditions data are compared, to test the added value of the cepstrum editing procedure and the robustness of the method when used on real data. To illustrate and validate the implemented methodology, data acquired during a long-term monitoring campaign of a wind turbine drivetrain are used.
Highlights
IntroductionThe susceptibility of structures to vibrations and the generation of tonalities is one of the main design issues in the field of rotating machinery
Cepstrum editing procedure must be combined with automated modal parameters estimation and tracking algorithms in order to perform automatic operational modal analysis (OMA) on continuous stream of data coming from a wind turbine drivetrain in real operating conditions
In order to test the performance of the automatic modal parameter estimator and the automatic cepstrum editing procedure on real data, the analysis of two data sets acquired with the turbine respectively in idling condition and running at normal operating conditions is performed and the results are compared
Summary
The susceptibility of structures to vibrations and the generation of tonalities is one of the main design issues in the field of rotating machinery. For this reason, eigenfrequencies, damping ratios, mode shapes and modal scaling factors are fundamental parameters for the design. Since damping and boundary conditions depend on the vibration amplitude and modal parameters depend on the (rotating) speed of the machine and its parts, it is important to experimentally verify the design values in normal operating conditions, that is, around operating points. Industrial design processes currently comprise full-scale machine testing and component-level-testing both in field and laboratory environments
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