Identification of Oscillation Vulnerable Buses Using Reflection Coefficient

The increasing penetration of renewable energy and power electronic devices has weakened grid strength by reducing system inertia and short-circuit capacity. In such weak-grid conditions, converter control loops interact with network impedance, causing oscillations across a wide frequency range from low-frequency to sub- and super-synchronous modes. This paper proposes an impedance-based reflection coefficient Γ method for the probabilistic pre-detection of oscillation-vulnerable buses before system disturbances occur. The method computes Γ from the system and load impedances at each bus and analyzes variations in its magnitude and phase with operating conditions (P,Q) Based on the Barkhausen stability criterion, buses showing abrupt phase changes are identified as oscillation-vulnerable points within the network. Simulation studies on the IEEE 39-bus using PSS/E verify the effectiveness of the proposed probabilistic pre-detection approach.