Tzounas, GeorgiosGeorgiosTzounasMilano, FedericoFedericoMilano2024-04-252024-04-252021 IEEE2021-01IEEE Transactions on Power Systems0885-8950http://hdl.handle.net/10197/25762This 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.EnglishTime Domain Integration (TDI)Delay Differential Algebraic Equations (DDAEs)Small Signal Stability Analysis (SSSA)Geometric approachJournal Article36146447310.1109/TPWRS.2020.30091722023-09-2015/IA/3074https://creativecommons.org/licenses/by-nc-nd/3.0/ie/