Time domain modeling of external systems for electromagnetic transients programs

A time domain method for accurate modeling of external power systems in electromagnetic transients programs (EMTPs) is presented. The time domain response of the external system to a multisine excitation signal is utilized to identify a discrete-time model for the external system. The identified model parameters are determined by least-squares estimation. The details of building both single-phase and multiphase equivalents are given. The validity of the equivalents is verified by comparing the electrical transients generated due to the energization of an open-ended line using the full and the equivalent external system. The method is being extended to multiport equivalents