A two-time scale simulation for dynamic analysis of power systems

This paper proposes a two-time scale simulation approach of both short-term and long-term dynamics in power systems. The short-term transient period is analyzed by a full-time scale simulation while a quasi-steady state model of the power system is used to simulate long-term dynamics. The proposed method is inspired of Singular Perturbation theory to model the interaction between the short-term and long-term dynamics. Based on this interaction, a suitable criterion to determine when the quasi-steady state model of a power system can be considered as a uniform approximation of the full-time scale model is proposed, which also determines the appropriate switching time between models. The proposed method is demonstrated on the 10-machine, 39-bus New England system and a 46-machine, 190-bus equivalent Mexican system.

► Simulation efficiency is achieved by both time step size adjustment and model reduction.
► The proposed criterion to automatically switch from the FTS to QSS models preserves a uniform approximation of state and algebraic variables.
► Initialization of state variables for the QSS simulation is not necessary.
► The proposed switching criterion is easily computed from the FTS simulation by monitoring the rate of change of the fast time-varying state variables.