Statistical Extrapolation Methods for Estimating Wind Turbine Extreme Loads

Investigation of Site-Specific Wind Field Parameters and Their Effect on Loads of Offshore Wind Turbines

“…In the literature and in the IEC standard it is recommended to choose a threshold which is the mean value plus 1.4 times the standard deviation (µ + 1.4σ) [4,9]. Moreover, determining an optimal threshold can lead to better fits of the distributions [11]. The aggregation of the peaks at each individual mean wind speed can be done by means of two procedures "fitting before aggregation" or "aggregation before fitting".…”

“…For the extracted and aggregated peaks, local distribution functions have to be fitted for each given mean wind speed v. In the literature, several distribution functions are used: three parameter Weibull (W3P), Weibull, normal, Rayleigh, Gumbel, etc. However, in general a W3P distribution function is preferred for the local distributions [5,11,12,27]:…”

“…Thereby, the largest value between each successive upcrossing of the threshold is extracted. Investigations have shown that the POT method yields superior results in comparison to the other methods [11,12]. In the literature and in the IEC standard it is recommended to choose a threshold which is the mean value plus 1.4 times the standard deviation (µ + 1.4σ) [4,9].…”

“…The way how these peaks are extracted and the selection of the fitting distribution function for the extracted peaks are very important. In the literature, several approaches are investigated [6][7][8][9][10][11][12]. Process methods describe the time series as a random process.…”

“…Process methods describe the time series as a random process. For this, the first four statistical moments-mean value, standard deviation, skewness and kurtosis-as well as a mean crossing rate of the observed time series are used [11,13]. Another type of extrapolation methods uses an inverse reliability approach.…”