Partitioned fitting and DC correction in transmission line/cable models for wideband EMT studies

This paper extends the applications of and provides further insights about partitioned fitting procedure. At the first stage of this procedure, the fitting is performed at a high frequency band by excluding frequency samples close to DC. The second stage finds a correction term for those excluded samples. This procedure achieves improved accuracy for the demonstrated case of transmission lines and cables used for HVDC transmission. The new approach complements the prevailing Universal Line Model (ULM) by reducing numerical instabilities due to large residue/pole ratios while delivering accurate DC response. This paper provides also time-domain implementation details of the state space realization obtained with partitioned fitting. The numerical stability performance of the improved fitting approach is demonstrated, through a set of test cases by applying different integration and interpolation schemes.