GumbelWind – statistical load extrapolation software
The structural dynamics of wind energy converters, especially those of large modern converters, is determined by low-frequency oscillation modi. The oscillations are stimulated by different forces, on the one hand by deterministic forces through the machine function, on the other by stochastic forces through the turbulent wind. The stochastic component of the resulting structural loads is always there and especially important in various situations which are typically responsible for extreme loads such as production states at high wind speeds and 50-year wind.
As a result of the stochastic nature of the loads additional statistic analyses must be performed in order to get extreme loads which have a well-defined probability of re-occurring. The basis for this evaluation is the extreme value theory from which a series of processes for practical use have been derived.
This fact was not taken into account for a long time in the wind energy converter guidelines. The third edition of the IEC 61400-1 (2005) now contains a section on statistic extrapolation of extreme loads. The approach described therein will become obligatory in the near future as part of the determination of loading assumptions and certification of wind energy converters.
With GumbelWind we have developed a program which fulfils the requirements of the IEC guideline and represents a tool for post-processing loads which permits the reliable and ultimately also less conservative determination of extreme loads.
General features of the program
- Load extrapolation based on the peak-over-threshold (POT) method
- Consistent use of the extreme value theory
- Determination of 50-year values in any stress resultant from simulations with turbulent wind
- Determination of simultaneous loads to a set confidence level
- Division of the windbins by medium wind speed and direction
- Simultaneous processing of production load traps (DLC 1.1) and 50-year wind (DLC 6.x) possible
- The program runs without user intervention
- an ASCII file controls the whole program flow
- direct processing of Flex5 simulations (int files)
- interfaces for other formats on request
- structured text file with all output data
- Header contains all information on the wind parameter load sensor-relevant output of the 50-year values with simultaneous loads in typical 6x6 format
- Output of the classical extreme evaluation for comparison
- Winbin-relevant output of the calculated distribution parameters
- Relative error standard permits assertions about approximation quality
- x2 adaptation test to avoid errors of the second tape
- percental participation of individual windbins at the 50-year level
- Gumbelwind – a computer code for statistical extrapolation of ultimate loads on wind turbines
- Lecture at the DEWEK2006
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