Subband transmission line modelling for robust power system transient simulation

A numerically robust, computationally efficient method for modelling a frequency-dependent transmission line (FDTL) by means of low-order transfer functions using a perfect reconstruction filter bank (PR-FB) is proposed. Modelling the delay-transfer functions associated with the characteristic impedance and weighting function of a FDTL 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 over the minimum pole (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.