Stability Assessment Method for DFIG-Based Wind Energy Systems

Power system stability can be threatened by severe transient disturbances. With the growing penetration of wind turbines in modern power systems, the development of effective real-time transient stability assessment methods for wind-dominated grids is becoming essential. Among the available wind turbine technologies in wind farms, Doubly-Fed Induction Generator (DFIG) is one of the most widely used solutions. Thus, this paper proposes a new method for assessing the transient stability of a single DFIG following large disturbances in a multi-machine power system. The presented method continuously monitors system stability by estimating the critical rotor-speed limit from the power–speed ($P_e$–${\omega }_r$) characteristic of the grid-integrated DFIG and subsequently using this limit to quantify the available stability margin. The measured rotor speed is then continuously compared with this computed critical speed. As soon as the speed exceeds this critical value, an unstable state is detected. A key advantage of this method is that it does not require predefined relay settings, detailed network parameters, or fault-clearing time information, making its deployment rather straightforward for protection applications. The proposed method is validated through comprehensive simulations using both a Single-Machine Infinite Bus (SMIB) system and a WSCC 9-bus multi-machine network under a wide range of scenarios. The simulation results demonstrate that the proposed method accurately estimates the critical rotor speed and reliably detects unstable conditions, even when the grid topology changes.