Torsional resonance active damping in grid tied wind turbines with gearbox, DFIG, and power converters

Two methods for torsional resonance mitigation are tested using the NREL software FAST in the MATLAB/Simulink environment with a 750 kW wind turbine. One mitigation method uses rotor angular acceleration measurements to provide virtual inertia for resonance detuning while the other is an active vibration absorber. The wind turbine representation uses a five mass gearbox model, a doubly fed induction generator model, an interface with the power grid, and an aerodynamic simulation of the tower shadow effect. The two mitigation methods are tested by subjecting the wind turbine to a frequency scan of wind in order to excite the resonant conditions and then to examine the influence of the mitigation methods. The vibration absorber shows better performance with greater shaft oscillation reduction than that of the virtual inertia. This is a continuation of an earlier study where a permanent magnet synchronous generator was included in the turbine model and no grid connection was present. The implementation of the vibration absorber includes a novel means of generator torque control for doubly fed induction generators.