Model based active damping of drive train torsional oscillations for a full-scale wind turbine nacelle test rig

This paper presents the design and implementation of a state-feedback control structure for active damping of drive train torsional oscillations in a 10 MW ground test facility for complete wind turbine nacelles. It is the rotor inertia emulation requirement for hardware-in-the-loop testing of wind turbines that introduces a high dynamic performance demand of up to 20 Hz for the driving torque application. This bandwidth is well beyond the inherent torsional characteristics of the mechanical chain and therefore active vibration damping is necessary. Therefore, the drive train has been modelled and an estimation-based torque control strategy has been proposed, taking into account torsional behaviour of the drive train. The proposed framework takes advantage of a constrained model predictive controller (MPC), explicitly considering the actuator physical limitation, while the unmeasured state-variables are to be provided by a Kalman filter. For an evaluation of the proposed approach, simulation results are provided and analysed. Furthermore, experimental tests have been performed on a scaled test rig providing a realistic test platform. Overall, the results confirm the achievement of control objective and that the proposed structure is effective and executable.