ISBN 9783843941556

978-3-8439-4155-6, Reihe Regelungstechnik

Steffen H. Raach
Lidar-assisted wake redirection control

163 Seiten, Dissertation Universität Stuttgart (2018), Hardcover, A5

Zusammenfassung / Abstract

Different research investigations in wind farm control have identified two promising operation concepts: axial induction control and wake redirection control.

Whereas the concept of induction control tries to minimize the impact of wakes on other wind turbines, the basic idea of wake redirection control is to redirect the wake of a wind turbine by yawing the wind turbine and therefore forcing a misalignment to the wind direction. Using this technique, interactions between wind turbines can be minimized. The current concept is based on an open-loop methodology in which a reduced-order wake model is used to pre-calculate the optimal yaw angles. This results in two disadvantages: The uncertainty which a simplified model introduces and the missing possibility to react to disturbances. This work introduces the concept of lidar-based closed-loop wake redirection control which can adapt to uncertainties and react on disturbances. Therefore, it extends the concept of wake redirection control with a new closed-loop methodology.

This work contributes various aspects to enable a lidar-based closed-loop wake redirection control. It first presents the general concept. Then it is separated in two subtasks: the measurement and the control tasks. First the measurement task is addressed and solutions are provided to process lidar measurement data to a useful signal for the wake redirection controller. Different methodologies are presented to track the wake position using lidar measurement data and the concept of model-based wake tracking is described in detail. Afterwards the control task is considered. Three different controller synthesis concepts are applied to wake redirection and controllers are synthesized. The different controllers are analyzed and the performances are assessed. Then they are verified in different simulation tools. Mainly simulations are performed with a medium-fidelity computational fluid dynamics simulation tool. In addition, the concept is implemented in a Large-Eddy simulation tool to demonstrate the adaption to disturbances and model uncertainties.

Altogether the work demonstrates the feasibility of the concept as well as the adaptivity of the controller. The different aspects of the concept are considered and methodologies for wake position estimation are provided and controllers are designed. Finally, recommendations are given to realize the concept in reality, and open questions are highlighted which require deeper investigations.