Discrete-Time Dynamic Model of NGH Damper

This paper presents a linearized discrete-time model of a pre-firing NGH damper based on the Poincare mapping technique. The performance of a pre-firing NGH damper can be predicted accurately with this model, including the possible undamping of off-tune torsional modes which has been reported in the literature. The paper analyzes two types of pre-firing schemes, one based on voltage zero crossings and the other based on a current synchronized phase-locked loop. The model is validated using digital simulation studies.