Harmonic Impact of Rectifiers Served by Unbalanced Three-Phase Sources

A converter is a rectifier or inverter which is intended to transfer electrical energy between AC and DC busses. A common industrial converter usually employs the familiar Graetz bridge configuration and usually has a rating in the kilowatt through lower megawatt range. The operation of such a device is nominally in the balanced three-phase mode in which the phase currents are nonsinusoidal. The Fourier series components of these currents, or harmonics, have been studied extensively, but relatively little has been done in the unbalanced operating mode. The principal goal of this research is to examine how unbalance in magnitude and phase of the AC supply alters the frequency spectrum of a line-commutated power converter. The topics considered in this thesis are for cases of small unbalance, infinite inductance in the DC circuit (Ldc = OO), and pure resistance in the DC circuit (Ldc= 0). Also, symmetrical component analysis is made, and reasons for the presence of uncharacteristic harmonics are studie