Rotational sampling in wind turbines: Difference between revisions

Revision as of 10:37, 28 May 2013

Revision as of 07:13, 29 May 2013

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== Background ==

Analysis of the loads on a wind turbine are usually carried out through use of power spectra. A power spectrum is defined as the power spectral density function of a signal plotted against frequency. The power spectral density function of a plot is defined as the Fourier transform of the covariance function.<ref>Remote sensing: models and methods for image processing, R. a. Schowengerdt</ref><ref>Remote Sensing: Models and Methods for Image Processing, Robert A. Schowengerd</ref> Regarding analysis of loads, the analysis involves time series, in which case the covariance function becomes the [[Autocovariance|autocovariance]] function. In the signal processing sense, the autocovariance can be related to the [[Autocorrelation|autocorrelation]] function.

== Deterministic processes ==

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The covariance function of a sum of sinusoids is itself a sum of sinusoidal functions. Thus, the power spectral density function is a set of Dirac delta functions. The locations of these are at multiples of ''n''. Thus, on a power spectrum, deterministic processes such as gravitational loading manifest themselves as spikes. This can be seen from analysing generator torque.

==== Blades ====