Low-frequency oscillation characteristics of wind power systems with interface including the stator dynamics

To quantify the oscillation characteristics of wind power systems, the stator dynamics of the induction generators is included. An interface including the stator voltage angle is given, changing the network parameter to the dq frame, which proves that the stator dynamics can not be ignored for practical systems with limited synchronous capacity. But the stator parameters can not be chosen as the state variables. The steady-state and dynamic stability models are derived with the proposed interface. It is found that the instable modes in wind power systems do not satisfy the electromechanical loop participation ratio, and can not be classified as the interarea modes among the synchronous generators. The participation factors shows the dependency of the oscillations on the induction generators, which is validated by the time-domain analysis. The dynamic response of the synchronous generators and the loads further validates that the oscillations are close to voltage oscillation instead of angular instability.