Polyphase transformer arrangements with reduced kVA capacities for harmonic current reduction in rectifier-type utility interface

Abstract

In this paper polyphase transformer arrangements with reduced AVA capacities are presented for harmonic current reduction in high power rectifier utility interface systems. Based on the concept of an autotransformer, a proposed twelve-pulse redfier system is realized with a resultant kVA rating of 0.18P0 @U). In this arrangement the rectifier diodes each conduct for 120 degrees per cycle and thefiflh and seventh harmonics are absent from the utility input line current. In the second scheme an eighteen-pulse rectifier is realized with the AVA rating of 0.16P0 @U), rectifier diode conduction of 120 degrees per cycle andfiph, seventh, eleventh and thirteenth harmonic cancellation in the utility line currents. Additional applications for the proposed polyphase transformer arrangements include twelve and eighteen-pulse systems feeding multiple six-pulse nonlinear loah, such as ac motor drives, with an appropriate phase shifl, and this arrangement substantially reduces the utility line current harmonics. For example, it is shown that the fiflh and seventh harmonics generated by two separate six-pulse nonlinear loads are subtracted, and this contributes to reduced distortion. Simulation results verifiing the proposed concept are presented.

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