Autotransformer configurations to enhance utility power quality of high power AC/DC rectifier systems

In this paper new autotransformer arrangements with reduced kVA capacities are presented for harmonic current reduction and to improve AC power quality of high current DC power supplies. A twelve-pulse AC to DC rectifier is proposed employing only 0.18P₀(pu) transformer kVA. The 5th and 7th harmonics are absent in the utility line currents. Further it is shown that conventional 12-pulse operation can be increased to 24 pulse with the introduction of tabs on the interphase reactor. Analysis and Simulation of the proposed schemes confirm the cancellation of lower order harmonics. Several example implementations of the proposed schemes for high current DC power supplies are shown. All of the above schemes provide clean power utility interface and complies with IEEE 519 recommended practices.