Active Torque Control for Gearbox Load Reduction in a Variable-Speed Wind Turbine

With the advent of power electronics, the size, weight, and cost of power converters have been drastically reduced while efficiency is improved. The use of variable-speed wind power generators has seen considerable growth. The use of gearboxes in the wind turbines allows for smaller size, lower weight, and higher speed generators. However, gearboxes have shown to be one of the least reliable components of the wind turbines. In this paper, we propose a method that can extend the life and reliability of wind turbine gearboxes by reducing the mechanical stress on gearbox components. Reduction of mechanical stress is achieved by the generator torque control that minimizes resonant torsional vibrations within a drivetrain caused by variations in wind velocity. A detailed model for the drivetrain of a 750-kW wind turbine, including a gearbox is presented. Experimental results are used to calculate the parameters of the gearbox. A controller is designed to adjust the generator torque at the end of the drivetrain to remove the unwanted and damaging torque variations from the drivetrain. Simulation results verify the effectiveness of the proposed method.