Small-Signal Models of Transmission Lines Oriented to the Impedance-Based Method

The increasing penetration of power electronics in electric networks has made the usage of detailed wideband models vital to study high-frequency oscillations, which other-wise would be almost impossible to detect. In this regard, the frequency-dependent effect of tie-lines has been considered a crit-ical feature in analyzing these troubles. However, incorporating them as small-signal impedance models is still a challenging task due to the non-rational of the model, so they are commonly approximated using lumped-parameter models or rational fit-ting techniques. Contributing to this area, the paper presents an improvement to the modeling of transmission lines (TL) computing their impedance models considering full frequency-dependency. Based on the hyperbolic relationships of voltage-current on the sending side of the TL and the Park transform, the impedance in $DQ$-domain is determined. This proposal does not rely on rational fitting nor repetitive time domain simulations. The effectiveness and accuracy of the proposal are validated through simulations in PSCAD-EMTDC.