Abstract
Abstract. The prospects of active wake deflection control to mitigate wake-induced power losses in wind farms have been demonstrated by large eddy simulations, wind tunnel experiments, and recent field tests. However, it has not yet been fully understood how the yaw control of wind farms should take into account the variability in current environmental conditions in the field and the uncertainty in their measurements. This research investigated the influence of dynamic wind direction changes on active wake deflection by intended yaw misalignment. For this purpose the wake model FLORIS was used together with wind direction measurements recorded at an onshore meteorological mast in flat terrain. The analysis showed that active wake deflection has a high sensitivity towards short-term wind directional changes. This can lead to an increased yaw activity of the turbines. Fluctuations and uncertainties can cause the attempt to increase the power output to fail. Therefore a methodology to optimize the yaw control algorithm for active wake deflection was introduced, which considers dynamic wind direction changes and inaccuracies in the determination of the wind direction. The evaluation based on real wind direction time series confirmed that the robust control algorithm can be tailored to specific meteorological and wind farm conditions and that it can indeed achieve an overall power increase in realistic inflow conditions. Furthermore recommendations for the implementation are given which could combine the robust behaviour with reduced yaw activity.
Highlights
IntroductionMore and more wind turbines have been installed in ever larger wind farms
In recent years, more and more wind turbines have been installed in ever larger wind farms
-called greedy turbine control seeks to optimize the operation of the individual turbines without taking into account the mutual effects on the other turbines, active wake deflection is the attempt to alter the trajectory of turbine wakes in order to improve the inflow conditions of downstream turbines
Summary
More and more wind turbines have been installed in ever larger wind farms. Downstream turbines are experiencing higher turbulence, which is generally associated with larger fatigue loads, and lower wind speeds, which results in a lower energy yield. One approach to achieve this is active wake deflection by intended yaw misalignment, which was already investigated by Medici and Dahlberg (2003) in a wind tunnel experiment. -called greedy turbine control seeks to optimize the operation of the individual turbines without taking into account the mutual effects on the other turbines, active wake deflection is the attempt to alter the trajectory of turbine wakes in order to improve the inflow conditions of downstream turbines. If two turbines are interacting through a wake, the deflection is achieved by deliberately introducing a yaw misalignment of the rotor of the upstream turbine with respect to the wind direction.
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