Combined Upwind/Downwind Plasma-Based Flow Control on a Vertical-Axis Wind Turbine

Abstract

Dynamic stall poses significant problems on vertical axis wind turbines (VAWTs) since the blades experience both large positive and large negative angles of attack. The resulting unsteady loads imposed on the drive-train and generator are primarily responsible for failures in the field. To control dynamic stall, a feed-forward control mechanism was designed and integrated with high-voltage, pulsed, dielectric barrier discharge (DBD) plasma actuators on a double-bladed VAWT. The actuators are pulsed to exploit flow instabilities in an on/off feed-forward configuration. A mechanical switch controlled a relay which switched between the earthed electrodes of the DBD plasma actuators which were placed on opposite sides of both VAWT blades. This enabled the high-voltage electrodes to generate plasma on alternating sides of the blades depending on which side was predicted to stall. As a result, dynamic stall was partially controlled by alternating actuators during continuous operation of the VAWT. Three types of tests were performed: actuation tests to find the output possible under different actuation conditions; tests to find the effective azimuth range of actuator operation; and transient tests to characterize the system's response. The results suggest that DBD plasma actuators have the potential to reduce unsteady loads and increase VAWT efficiency.