Final colloquium Zekai Chen

LiDAR Enhanced Closed-loop Active Wake Mixing Control

Supervisor: prof. dr. ir. J.W. van Wingerden 

Abstract: Wind energy plays an essential role in the sustainable development of our future. In wind farms, where multiple turbines operate in arrays, turbines are subject to the wake effect—a phenomenon of aerodynamic interactions that significantly reduces power production in downstream turbines, increases structural loading, and shortens turbine lifespan. To mitigate these challenges, wake mixing control strategies are employed to enhance the mixing of free-stream air with the turbine wake, thereby improving overall wind farm performance. Among these strategies, the Helix approach has garnered attention for its consistent mixing of high- and low-energy air, leading to substantial increases in downstream turbine power production. Currently, the Helix approach is implemented in an open-loop manner. This is not an issue under uniform wind conditions. However, in the presence of external uncertainty such as wind shear and turbulence, the effectiveness of the Helix is compromised, occasionally causing more harm than benefit. This reveals an urgent demand for a closed-loop control method. Consequently, this work developed a closed-loop active wake mixing framework that integrates LiDAR as the feedback mechanism to measure the flow information. The framework consists of a LiDAR subsystem for real-time flow data acquisition and processing, and a control subsystem for managing the complex system with time-delay in real-time. The designed framework is simulated in QBlade under different wind conditions. Results demonstrate that it effectively rectifies the Helix under some external disturbances and improves power production in a two-turbine setup under shear and combined shear-turbulence conditions. However, limitations are noted in handling high-frequency disturbances. Despite these limitations, the proposed framework demonstrates great potentials, offering a novel perspective in deploying wake mixing strategies. It provides a platform for integration with other control strategies, such as phase synchronization, to further improve the wind farm performance.