A New Approach to Improve Power factor and Reduce Harmonicsin a Three-Phase Diod Rectifier Type Utility Interface

this paper, a new approach to improve power factor and reduce harmonics generated by a three-phase diode rectifier type utility interface is proposed. The proposed approach is passive and consists of a novel interconnection of a star / delta transformer between the ac and dc sides of the diode rectifier topology (see Fig. 1). This novel interconnection, in combination with the 120° conduction intervals of each diode, is shown to generate a circulating third harmonic current between the ac and dc side of the rectifier bridge. The circulating third harmonic current between the ac and dc side of the rectifier bridge. The circulating third harmonic current is then shown to drastically improve the performance of the diode rectifier type interface. The resulting input current is near sinusoidal in shape with significant reduction in line current harmonics. The proposed system can be viewed as a cost-effective retrofit to the existing diode rectifier utility interface applications. Analysis and design of the proposed approach are examined in per-unit quantities. A suitable design example illustrates the sizing of the necessary passive components. Selected results are verified experimentally on a laboratory prototype system.