Influence of atmospheric conditions on the power production of utility-scale wind turbines in yaw misalignment

Abstract

The intentional yaw misalignment of leading, upwind turbines in a wind farm, termed wake steering, has demonstrated potential as a collective control approach for wind farm power maximization. The optimal control strategy and the resulting effect of wake steering on wind farm power production are in part dictated by the power degradation of the upwind yaw misaligned wind turbines. In the atmospheric boundary layer, the wind speed and direction may vary significantly over the wind turbine rotor area, depending on atmospheric conditions and stability, resulting in freestream turbine power production which is asymmetric as a function of the direction of yaw misalignment and which varies during the diurnal cycle. In this study, we propose a model for the power production of a wind turbine in yaw misalignment based on aerodynamic blade elements, which incorporates the effects of wind speed and direction changes over the turbine rotor area in yaw misalignment. The proposed model can be used for the modeling of the angular velocity, aerodynamic torque, and power production of an arbitrary yaw misaligned wind turbine based on the incident velocity profile, wind turbine aerodynamic properties, and turbine control system. A field experiment is performed using multiple utility-scale wind turbines to characterize the power production of yawed freestream operating turbines depending on the wind conditions, and the model is validated using the experimental data. The resulting power production of a yaw misaligned variable speed wind turbine depends on a nonlinear interaction between the yaw misalignment, the atmospheric conditions, and the wind turbine control system.

Results from a Wake Steering Experiment at a Commercial Wind Plant: Investigating the Wind Speed Dependence of Wake Steering Performance

“…Through a wake steering field experiment, Doekemeijer et al (2021) observe asymmetry in the power loss as a function of yaw misalignment, similar to the findings of Howland et al (2020), while also noting a relatively flat peak of the power curve as a function of yaw offset followed by a sharp drop in power production for more extreme offsets.…”

“…16 reveals the impact of yaw misalignment on power production for a specific wind turbine, recent research suggests that the relationship between yaw misalignment and power depends on the atmospheric boundary layer as well as the turbine's control system. Howland et al (2020) show how the power production of a misaligned wind turbine depends on the wind shear and veer profiles interacting with the rotor, which can introduce asymmetry in the relationship between yaw misalignment and power. The authors also explain how the generator torque control logic used during below-rated operation can influence the impact of yaw misalignment on power via changes in rotor speed.…”

Large-eddy simulation on the similarity between wakes of wind turbines with different yaw angles

“…the modified TSRλ was fixed. However, if another control strategy is employed, the thrust T and the power P may follow cos a γ and cos b γ , respectively, with a < 2 and b < 3 (Bastankhah & Porté-Agel 2019;Howland et al 2020;Liew, Urbán & Andersen 2020). Making the comparison in figure 3 is just to verify the implementation of this idealized rotor control rather than indicating that the power and thrust should vary in that way in real-life applications.…”

Wind farm yaw control set-point optimization under model parameter uncertainty

“…where N f is the number of upwind turbines and the power production isP j = 1 2 ρAC P u 3 e,j . In this study, C P = C P (γ = 0) • cos Pp (γ) is used although the recently developed blade-element model which accounts for wind velocity profiles could be used in future studies with rotational turbine models 29 . For the utility-scale wind farm numerical experiments, P p = 2, which represents a reasonable first order approximation of C p (γ) as shown in a yaw misalignment field experiment at the same wind farm 29 .…”