A Modified Loss of Synchronism Condition for Efficient Critical Clearing Time (CCT) Estimation in Transient Stability Analysis

Accurate determination of critical clearing time (CCT) remains a fundamental challenge in transient stability analysis of power systems, primarily due to the highly nonlinear and complex dynamic behavior of multimachine networks. Existing methods based on the loss of synchronism (LOS) condition often require intensive numerical iterations and may suffer from convergence issues, particularly near the critical stability boundary. To address these limitations, this paper proposes a novel CCT estimation approach based on the critical trajectory method with a modified loss of synchronism (MLOS) condition. Unlike conventional LOS methods, the proposed MLOS approach linearizes the critical condition by assuming that the directional variation of the eigenvector associated with the zero eigenvalue of the Jacobian matrix is negligible, allowing it to be approximated as an identity matrix. This modification simplifies the critical trajectory formulation, significantly reduces the computational burden, and improves the numerical stability of the CCT determination process without sacrificing accuracy. Simulation results conducted on multiple benchmark test systems demonstrate that the proposed MLOS method achieves higher computational efficiency and comparable, if not superior, accuracy relative to traditional LOS‐based approaches. These results highlight the effectiveness and robustness of the MLOS method, making it a promising tool for accurate and efficient transient stability assessment in modern power systems.