Research for approximation algorithm of high-frequency model of transformer windings

To obtain order-reduced model of high-frequency transformer windings, firstly voltage transfer functions are derived from short-circuit admittance parameters which are calculated from the distributed parameters or measured parameters of transformer windings in this paper. Secondly, voltage transfer functions are fitted with rational functions by vector fitting method. Lastly common Pade algorithm, Routh algorithm and optimal Pade approximation algorithm are order-reduced for rational voltage transfer functions to obtain approximate model of transformer windings. Simulation results show optimal Pade approximation algorithm not only can reserve main magnitude-phase characteristics of high-frequency model, but also can simplify high-frequency model. So this algorithm is the fittest algorithm for gaining order-reduced model at present.