Harmonic Norton equivalent for the magnetising branch of a transformer

Abstract

In the analysis of harmonic power flows, the transformer is generally represented as a passive component. However, due to the magnetisation nonlinearity, the transformer constitutes a source of harmonic currents which can aggregate and cause substantial waveform distortion. This paper describes the development of a Norton equivalent circuit which accurately represents the transformer magnetising branch in harmonic power-flow studies. It is shown that even in the absence of other nonlinearities in the system, the transformer magnetising current can give rise to considerable harmonic voltage levels.