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Wind Energy Science The interactive open-access journal of the European Academy of Wind Energy
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Discussion papers
https://doi.org/10.5194/wes-2018-68
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wes-2018-68
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research articles 16 Jan 2019

Research articles | 16 Jan 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Wind Energy Science (WES).

Detection and characterization of extreme wind speed ramps

Ásta Hannesdóttir and Mark Kelly Ásta Hannesdóttir and Mark Kelly
  • DTU Wind Energy Dept., Technical University of Denmark, Roskilde, Denmark

Abstract. The present study introduces a new method to characterize ramp-like wind speed fluctuations, including coherent gusts. This method combines two well-known methods: the continuous wavelet transform and the fitting of an analytical form based on the error function. The method provides estimation of ramp amplitude and rise time, and is herein used to statistically characterize ramp-like fluctuations at three different measurements sites. Together with corresponding amplitude of wind direction change, the ramp amplitude and rise time variables are compared to the extreme coherent gust with direction change from the IEC wind turbine safety standard. From the comparison we find that the observed amplitudes of the estimated fluctuations do not exceed the one prescribed in the standard, but the rise time is generally much longer, on average around 200 s. The direction change does however exceed the one prescribed in the standard several times, but for those events the rise time is a minute or more. We also demonstrate a general pattern in the statistical behavior of the characteristic ramp variables, noting their wind speed dependence, or lack thereof, at the different sites.

Ásta Hannesdóttir and Mark Kelly
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Ásta Hannesdóttir and Mark Kelly
Ásta Hannesdóttir and Mark Kelly
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Short summary
The wind turbine safety standard includes a coherent gust model with a wind speed increase and direction change of 10 seconds. With the increasing rotor size of modern wind turbines this model is criticized for being uniform across these large rotors. In this study we investigate measurements of coherent gusts with a ramp-like increase in wind speed. We define a new method for ramp detection and characterization and compare with the coherent gust model from the wind turbine safety standard.
The wind turbine safety standard includes a coherent gust model with a wind speed increase and...
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