A control algorithm for the deepwind floating vertical-axis wind turbine

Abstract

A generator torque control system was developed for the Deepwind floating vertical-axis wind turbine. Deepwind is a spar platform of a unique design. The generator is mounted underwater at the base of the spar, which functions as the main driveshaft. Despite the novel configuration, it is shown that a simple proportional-integral (PI) control system is able to successfully regulate the generator torque, over the full operating range of the turbine. Moreover, a simple linearized model, including only yaw degrees-of-freedom of the rotor/spar and stator, captures the most important dynamics for purposes of designing and tuning the control system. Two torque-speed operating schedules are compared, one with a conservative constant rotational-speed cutoff, and the other with a higher maximum speed. The latter increases energy capture, in exchange for more severe fluctuations in generator torque and mooring system yaw. The control system has little influence over the platform tilt angle.