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Research articles 02 Jul 2018

Research articles | 02 Jul 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Wind Energy Science (WES).

Robust active wake control in consideration of wind direction variability and uncertainty

Andreas Rott1, Bart Doekemeijer2, Janna Seifert1, Jan-Willem van Wingerden2, and Martin Kühn1 Andreas Rott et al.
  • 1ForWind - Center for Wind Energy Research, Institute of Physics, University of Oldenburg, 26129 Oldenburg, Germany
  • 2Delft Center for Systems and Control, Delft University of Technology, 2628 CD Delft, the Netherlands

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 of current environmental conditions in the field and the uncertainty of 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 met 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 optimise 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.

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Andreas Rott et al.
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Short summary
Active wake deflection (AWD) aims to increase the power output of a wind farm by misaligning the yaw of upstream turbines. I analysed the effect of dynamic wind direction changes on AWD. The results show, that AWD is very sensitive towards these dynamics. Therefore, I present a robust active wake control, which considers uncertainties and wind direction changes, increasing the overall power output of a wind farm. A side effect is a significant reduction of the yaw actuation of the turbines.
Active wake deflection (AWD) aims to increase the power output of a wind farm by misaligning the...