Dynamic wind turbine wake trajectory control: Strategies and real-time validation

Date

2019-08

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Abstract

Wind farm control has demonstrated power production enhancements using yaw-based wake steering. However, slower yaw actuation rates compared to inflow change rate cause time-varying downstream-rotor-wake overlap conditions, diminishing its benefits. To accommodate for inflow variations, closed-loop wake control can be an effective approach to minimize wake trajectory uncertainty. In this regard, the contribution of this dissertation represents preliminary work in the construction of closed-loop wake control, where the contribution is focused on the development and validation of its fundamental building blocks: wake actuation and wake position detection.
To emulate the full-scale physics of wake control based on changes in real time, the wind tunnel-based platform HAWKS, equipped with a fully controllable model wind turbine and advanced flow monitoring system, was developed and its wake prediction capabilities were validated. In regard to the wake actuation, this dissertation proposes a novel wind turbine yaw-based wake steering method that incorporates rotor speed control, a much faster control action, to reduce wake deflection oscillations caused by variable inflow direction. It was found that the variable inflow direction causes proportional changes in the cross-stream thrust component leading to wake trajectory variations. This wake trajectory stabilization method is based on counteracting the inflow cross-stream thrust effect by altering the rotor speed. In regard to the wake position detection, this dissertation proposes the tip-vortex-based tracking approach, which tracks the instantaneous strengths of the streamwise 1P spectral energy peaks as the wake interface oscillate around a desired position.
It was demonstrated through wind tunnel experiments that yaw-based wake steering statically applied in combination with speed control effectively improves the mixing or momentum transport leading to enhance wake recovery and counteracts the dynamic cross-stream thrust component induced by variable inflow direction. The tip-vortex-based tracking approach revealed wake oscillation reduction around a desired position resulting from static yaw

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Keywords

Wind turbine wake, Wake control, Wind farm control, Wake steering, Wake detection

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