Operational Modal Analysis of the Nordex Karahka 04 Wind Turbine Tower

Kurzfassung

This document presents the modal analysis results performed on the Nordex Karahka 04 wind turbine tower in the rotating and idling regimes. Structural response data is acquired by ten accelerometers positioned on the tower at five different heights. System identification is conducted in the time-domain within the operational modal analysis (OMA) framework using stochastic subspace identification (SSI) and mode tracking. It is possible to determine the eigenfrequency, damping ratio and mode shape of the following modes of vibration: 1. first fore-aft tower bending mode 2. first side-side tower bending mode 3. second fore-aft tower bending mode 4. second side-side tower bending mode The report describes the data acquisition, data selection and data inspection pre-processing steps. The operational modal analysis procedure is explained using measured data sets as examples. The modal analysis results are presented and discussed for both operating regimes. The full modal analysis results are available in electronic format.