A new approach to improve power factor and reduce harmonics in a three phase diode rectifier type utility interface

摘要

A novel approach to improving power factor and reducing harmonics generated by a three-phase diode-rectifier-type utility interface is proposed. This approach is passive and consists of a novel interconnection of a star/delta power transformer between the AC and DC sides of the diode rectifier topology. This interconnection, in combination with the 120 degrees conduction intervals of each diode, is shown to generate a circulating third-harmonic current between the AC and DC side of the rectifier bridge. This current is shown to drastically improve the performance of the diode-rectifier-type interface. The resulting input current is near-sinusoidal, 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. A design example illustrates the sizing of the necessary passive components. Selected results were verified experimentally on a laboratory prototype system.