Wideband Transformer Model Based on Combined Fitting Method

This paper addresses the transformer modeling problem by proposing a new method for establishing a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{\pi}$</tex> -type equivalent circuit of transformers and developing a wideband <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{\pi}$</tex> - type equivalent circuit. The proposed method combines the Matrix Pencil Method (MPM) and Vector Fitting (VF) technique, enabling automatic order determination while maintaining the high-accuracy characteristics of the VF technique. Specifically, the method involves using the MPM method to determine the order and calculate the initial poles, followed by applying the VF technique to compute the corresponding parameters for fitting. A wideband nonlinear transformer equivalent circuit model considering the ferromagnetic and frequency-dependent characteristics of transformers was established. Simulations validated the model's accuracy, showing that the proposed method outperforms the individual application of the MPM and VF techniques.