Delay-Based Decoupling of Power System Models for Transient Stability Analysis

This paper proposes a delay-based method to reduce the coupling of the equations of power system models for transient stability analysis. The method consists in identifying the variables that, when subjected to a delay equal to the time step of the numerical integration (one-step delay), leave practically unchanged the system trajectories. Automatic selection of the variables based on a geometric controllability/observability approach and estimation of the maximum admissible delay are duly discussed. Such a one-step-delay approximation increases the sparsity of the system Jacobian matrices and can be used in conjunction with state-of-the-art techniques for the integration of differential-algebraic equations. The proposed approach is evaluated in terms of accuracy, convergence and computational burden, by means of the New England 39-bus system; a 21,177-bus model of the ENTSO-E transmission system.