  Traditional dynamic security assessment faces challenges as power systems are
experiencing a transformation to inverter-based-resource (IBR) dominated
systems, for which electromagnetic transient (EMT) dynamics have to be
considered. However, EMT simulation is time-consuming especially for a large
power grid because the mathematical model based on detailed component modeling
is highly stiff and needs to be integrated at tiny time steps due to numerical
stability. This paper proposes a heterogeneous multiscale method (HMM) to
address the simulation of a power system considering EMT dynamics as a
multiscale problem. The method aims to accurately simulate the macroscopic
dynamics of the system even when EMT dynamics are dominating. By force
estimation using a kernel function, the proposed method automatically generates
a macro model on the fly of simulation based on the micro model of EMT
dynamics. It can flexibly switch between the micro- and macro-models to capture
important EMT dynamics during some time intervals while skipping over other
time intervals of less interest to achieve a superior simulation speed. The
method is illustrated by a case study on a two-machine EMT model to demonstrate
its potential for power system simulation.
