Harmonic Modeling of Transformer Cores Based on the Fingerprint-Measurement

This paper presents a novel method for charac-terizing the model structure as well as estimating the model parameters for transformer cores. The basic idea of the method is to use the fingerprint technique to characterize the behavior of the device under test based on the terminal measurements. The harmonic fingerprint technique describes how each harmonic current is affected by each possible form of harmonic voltage background. In this paper, the model structure for transformer cores is discussed on the basis of the reflected currents at the terminal for different voltage harmonics. Accordingly, the harmonic behavior of the transformer core can be represented by a linear Norton equivalent model assuming frequency decoupling. In addition, a novel method for estimating the parameters of the Norton equivalent model for the transformer core is proposed. The performance and accuracy of the proposed method have been verified and validated for an exemplary transformer core using the measured harmonic voltage-current pairs and model characteristics.