Optimal (Dynamic) Turbine Repositioning Strategies for a Floating Wind Farm Depending on Mooring Line Stiffness

Abstract

In the pursuit of mitigating the wake effect, floating wind turbines have additional degrees of freedom compared to their fixed-bottom counterparts. The mooring system with which floating wind turbines are anchored to the seabed allows a range of motion in which turbines can be repositioned. Turbine repositioning uses yaw control to reposition floating wind turbines, and to thereby actively optimize the wind farm layout. Previous research has focused on obtaining optimal steady-state yaw angles for turbine repositioning by using steady-state wake models. Here, the primary conclusion is that mooring line tension needs to be relaxed to facilitate a range of movement large enough for steady-state turbine repositioning to be effective. The presented work studies the effect of using dynamic yaw signals for turbine repositioning by using a dynamic wake model. To study the effect of including wake dynamics, an optimization problem to find the optimal yaw control signals for a two turbine floating wind farm is solved for various mooring configurations. This work shows that for stiffer mooring configurations, turbine repositioning can still be leveraged to increase wind farm efficiency, but that the optimal yaw control action is dynamic for these cases.