Transient stability studies of doubly-fed induction generator using different drive train models

Three equivalent drive train models of a wind turbine generator (WTG) are presented in this paper. The flexibility of the blades bending and the drive train are considered to analyze its transient stability under a three-phase fault. The simulations show that the fifth order lumped-mass model provides too optimistic estimation while the ninth order three-mass model can observe the motion of shaft system, which is more suitable for transient stability analysis. When a WTG is perturbed, a large torque may be produced in the drive train which may result in torsional oscillations between different parts of the WTG shaft system, and thereby reduce the fatigue life of the shaft due to bearing the large torque repeatedly.