Active Control for Wind-Turbine Power Enhancements in Unsteady Inflow Conditions

Exposure to unsteady inflow conditions is a prevalent aerodynamic situation for wind energy systems, particularly in floating offshore wind turbines experiencing streamwise platform oscillations. Previous literature has demonstrated potential for period-averaged power generation enhancements by leveraging these unsteady flows, but little work has been done to examine the effects of active control methods in these conditions. In this study, we investigate the impacts of active blade-pitch angle and generator torque control during exposure to oscillating inflow velocities. Experiments are conducted in a fan-array wind tunnel, using a custom-built model wind turbine with a diameter-based Reynolds number of 270,000. Phase-averaged power generation is compared for a variety of open-loop control strategies, evaluating efficiency across different control amplitudes and phase-shifts relative to the unsteady inflow. Relevant turbine aerodynamics are subsequently examined to develop a theoretical framework for predicting optimal open-loop control methods. Demonstrating additional power-enhancement opportunities, this work establishes a foundation for future closed-loop turbine control methods, applicable in a variety of full-scale wind energy systems under unsteady inflow conditions.