Subband, universal line and cable modeling for robust power system transient simulation

A numerically robust, computationally efficient method for modeling a multi-phase, frequency-dependent transmission line (FDTL) or underground cable (FDUC) by means of low-order transfer functions using a perfect reconstruction filter bank (PR-FB) is proposed. Modeling the delay-transfer functions associated with the characteristic impedance and weighting function of an FDTL or FDUC over a wide range of frequencies typically involves high-order rational function approximations (RFAs). Discretization of the high order RFAs is prone to numerical instability, especially when the ratio of the maximum pole magnitude over the minimum pole magnitude (condition number) is large. The proposed method improves numerical stability by employing several narrowband (subband) low-order RFAs using a logarithmic tree-structured perfect reconstruction filter bank. Moreover, the method is computationally efficient, since simulation of each subband is of low complexity and very suitable for parallel (multi-core) processing.