DC Magnetic Deviation, and its Suppression, of a Matching Transformer in a Series Active Filter

This paper deals with a series active filter for harmonic-current compensation of a large-capacity diode rectifier with a capacitive load. Flux satulation may occur in a series matching transformer for connecting the series active filter to the ac side of the diode rectifier. This paper develops an analog controller of a dc magnetizing current flowing in the matching transformer, along with a model for the controller, to avoid the flux satulation. Operating characteristics of the controller are theoretically and exprimentally discussed, taking into account both an offset voltage in the controller and an error in a current sensor. Finally, this paper discusses a relation between magnetizing characteristics of the matching transformer and the amplitude of the magnetizing current.