Control of a Wind Turbine with a Magnetic Continuously Variable Transmission for Mitigation of Torque Variations

Advances in wind turbine technology have allowed the machines to take advantage of economies of scale. The increased size and power requirements of modern turbines have presented new challenges to the more expensive components, particularly the gearboxes. This paper focused on a new control system for wind turbines in above-rated, or Region 3, wind regimes. The control goals were to regulate the generator speed and protect the gearbox and generator by mitigating drivetrain torque variations. This paper explains the development of a linear wind turbine model that was largely based on the National Renewable Energy Laboratory’s Fatigue Aerodynamic Structures Turbulence (FAST) 5 megawatt model. A simplified magnetic continuously variable transmission (CVT) was included in the wind turbine model. A multi-input linear quadratic regulator (MI LQR) controller was developed and simulated. Simulations of the multi-input controller demonstrated large improvements in speed regulation and torque variation reduction when compared to industry standard proportional-integral blade pitch controllers. Results from this proof of concept study indicated that the use of a magnetic CVT coupled with a multiinput LQR controller may have the potential to reduce fatigue and thereby extend the lifetime of wind turbine components.