Alleviation of excess fatigue loads due to vibrations in the drive-train of wind turbines can be achieved through the use of torsional vibration dampers. Two torsional dampers based on different design approaches were designed and assessed: the first employs a conventional band-pass filter technique, whereas the second involves an alternative model-based approach. Frequency domain analyses were carried out on the system with the two dampers for the cases with and without model uncertainty. The system using the band-pass filter-based damper showed deterioration in stability and performance when subjected to uncertainty in the model and had to be re-tuned to recover a good damping performance. Conversely, the system employing the model-based damper maintained good stability and superior damping performance in the presence of model uncertainties. These attributes can ensure that the damper exhibits a good performance even if the wind turbine parameters vary during operation, such as when ice forms on the blades. Time domain simulations were carried out to verify the frequency domain analyses. © 2014 The Authors. Wind Energy published by John Wiley & Sons, Ltd.