Open AccessAn algorithm for fitting passive equivalent circuits for lumped parameter frequency dependent transmission line models
Author(s) -
Challa Kiran Kumar,
Gurrala Gurunath,
Mukherjee Pritam
Publication year - 2021
Publication title -
iet generation, transmission and distribution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.92
H-Index - 110
eISSN - 1751-8695
pISSN - 1751-8687
DOI - 10.1049/gtd2.12172
Subject(s) - emtp , equivalent circuit , transmission line , frequency response , electrical impedance , electric power transmission , step response , line (geometry) , transient response , rational function , modal , mathematics , algorithm , control theory (sociology) , voltage , mathematical analysis , engineering , computer science , physics , electric power system , electrical engineering , geometry , materials science , power (physics) , control (management) , quantum mechanics , control engineering , artificial intelligence , polymer chemistry
Accurately fitting rational functions to the frequency response of modal impedances is crucial for including frequency dependency in lumped parameter models of transmission lines. Vector fitting is widely used for fitting rational functions to the frequency response of modal impedances and then an R‐L equivalent circuit is obtained from the rational functions. A single‐step method based on the properties of Foster equivalent circuit is proposed to directly fit an R‐L equivalent circuit to the frequency response of modal impedances. The positive peaks, negative peaks and the positive zero crossings of the slope change plot of the frequency response are found to provide a good approximation of zeros, poles and the flat region locations of the frequency response. An enhanced fitting algorithm is proposed based on these observations. A close enough fitting is achieved using the proposed method with less number of passive elements. Using the proposed model in EMTP‐RV, 400, 765, 1200 kV transmission lines and a 11‐bus 500 kV network are simulated for switching transients. The results are compared with the constant parameter cascaded π ‐model and the Frequency‐dependent line model in EMTP‐RV. The switching transient results of the proposed model are found to be comparable to the Marti's model in EMTP‐RV.