Real-time system strength estimation using PMU data for modern grids with high IBR penetration

With the increasing penetration of Inverter-Based Resources (IBRs) in power grids, real-time estimation of system strength has become a critical requirement for system operators to ensure grid stability and reliability. This paper introduces a robust method for system strength estimation using Phasor Measurement Unit (PMU) data, eliminating the need for model-based information. The proposed approach leverages Thevenin equivalent parameters to evaluate system strength at a specific bus. To address the phase angle drift in voltage and current measurements caused by continuous system frequency variations, corrections are applied, followed by synchronization of three consecutive phasor measurements to a common reference frame. These synchronized measurements are used to compute Thevenin equivalent parameters. Key features of the proposed method include a novel directional detection algorithm that addresses the impact of power flow directions on system strength estimation, ensuring accurate real-time evaluation. Unlike previously published literature, which primarily focused on system strength estimation at load buses, this method provides a comprehensive approach applicable across various operating scenarios. Additional enhancements, such as outlier removal through advanced filtering techniques, further improve the robustness and practical applicability of the approach. Validation using actual field PMU data from 161 kV, 275 kV and 500 kV systems demonstrates its effectiveness, while integration into a Wide Area Monitoring System (WAMS) platform underscores its readiness for operational use. Results from simulations and field data confirm the reliability and accuracy of the method for real-time applications in modern grids.