Comparison of actuation methods for wake control in wind plants

In recent research, cooperative wind turbine control strategies have been proposed to optimize overall performance of wind plants by taking into account the aerodynamic interaction effects that the wind turbines have on each other through their wakes. Wind plant control strategies have different ways of using the control degrees of freedom (DOFs) of the turbine. Conventional control DOFs of a wind turbine are the pitch angles of the blades, the generator torque, and the yaw angle of the rotor. In most wind plant control approaches in literature, the generator torque and/or blade pitch control DOF is used to affect the wake velocity deficit (referred to as axial-induction-based control). In recent studies, an alternative control method was used, in which the direction of the wake is changed using the yaw DOF such that the overlap of the wake with downstream rotors is avoided or reduced (wake redirection control). In this paper, we present a high-fidelity, computational fluid dynamics simulation case study, in which the potential of both control methods is compared, in terms of their effect on power production of a two-turbine setup. For the flow conditions and turbine considered in the case study, wake-redirection control is shown to have a larger potential to improve wind plant energy production than axial-inductionbased control. An additional analysis shows that causes for the difference in potential are wake expansion and meandering.