Modeling of turbulence within wind farms with 100 or more wind turbines is important both for extreme and fatigue limit states. Behind a wind turbine a wake is formed where the mean wind speed decreases slightly and the turbulence intensity increases significantly. This increase in turbulence intensity in wakes behind wind turbines can imply a significant reduction in the fatigue lifetime of wind turbines placed in wakes. In this paper the design code model in the wind turbine code [IEC 61400-1, Wind turbine generator systems - Part 1: Safety requirements. 2005] is evaluated from a probabilistic point of view, including the importance of modeling the SN-curve by a bi-linear model. Fatigue models relevant for welded, cast steel and fiber reinforced details are considered. Further, the influence on the fatigue reliability is investigated from modeling the fatigue response by a stochastic part related to the ambient turbulence and the eigenfrequencies of the structure and a deterministic, sinusoidal part with frequency of revolution of the rotor.
Udgivelsesdato: OCT