Operational Modal Analysis and Mode Tracking of the WiValdi OPUS-2 Wind Turbine

Kurzfassung

The present paper investigates the experimental determination of the parameter-dependent eigenfrequency, damping ratio and mode shapes of the parked WiValdi OPUS-2 wind turbine using operational modal analysis. A data-driven dynamic model is constructed as a function of environmental and operational parameters. Accelerometers are placed on both the rotor and the tower to allow a better separation of eigenmodes. Data is collected over one year to cover a wide parameter space. More than twenty eigenmodes can be identified and tracked in the lower frequency range. It is possible to separate closely-spaced modes such as the tower fore-aft and side-side bending. Detailed results are presented for the first two tower bending modes, the two first rotor collective modes and the first rotor asymmetric mode. The damping ratio is shown to have a direct dependency on wind speed and yaw misalignment.