Abstract:
Simulations of wind turbine wakes are important for wind farm layout design
and the development of wind farm control strategies to optimise the power
output and reduce fatigue loading of the turbines. This study uses a coupled
Large Eddy Simulation (LES) and turbine aeroelastic tool to evaluate the
impact of wake turbulence on turbine fatigue loading and control response in
a thermally stratified atmospheric boundary layer (ABL). LES models of the
ABL and of a group of turbines in the Anholt offshore wind farm are developed
which are in good agreement with the field data for both mean wind profiles
and wind turbine array power outputs.
The simulations of an idealised four inline turbine array for both below- and
above-rated operations show that the fatigue loads on the drivetrain torsion
and yaw bearing moment, as well as the blade pitch rate, of the downstream
turbines are higher under the neutral ABL compared to the unstable ABL. A
baseline active yaw controller causes higher fatigue on turbines in the wake
compared to the fixed yaw turbine case, without any increase in the power
output. The study on the effects of large directional wind shear in a stably
stratified ABL on the wake interaction suggests that the wake rotations are
affected by the lateral velocity of the ambient wind, which causes differences
in radial wake expansion and wake shape twist angle. The implementation of
Individual Pitch Control (IPC) on downstream turbines is found to reduce
the flapwise blade-root bending fatigue by up to 20% for both symmetric and
skewed wake cases.
