Impedance modeling of doubly-fed induction generators

This work presents sequence impedance models of Type-III wind turbines based on doubly-fed induction generators (DFIG). The models take into account the effects of both stator- and rotor-side converters as well as their control, including the phase-locked loop (PLL) and current control. The models are developed using the harmonic linearization method which has previously been applied to Type-IV turbines and HVDC converters. The developed models are validated by point-by-point simulation of the detailed switching model and also used to analyze subsynchronous oscillation of Type-III turbines with series-compensated grid.