New clean power rectifier systems for utility interface of static converters

Large harmonics, poor power factor and high total harmonic distortion (THD) in the utility interface are common problems when nonlinear loads such as adjustable speed drives (ASD) and power supplies are connected to electric utilities in large numbers.; In response to these concerns, this dissertation proposes several robust three phase rectifier topologies which draw near sinusoidal currents from the utility at unity power factor. A low kVA 12-pulse rectifier system is first proposed, which results in cancellation of 5,7 harmonic currents in the utility line. The polyphase transformer in the proposed 12-pulse system is rated at 82% smaller than that in the conventional system. This contributes to lower cost, weight and volume.; A 24-pulse rectifier system is then introduced. In this system harmonics up to 23{dollar}sp{lcub}rm rd{rcub}{dollar} are cancelled in the utility line currents. A unique tapped interphase transformer with two additional diodes is shown to extend the 12-pulse operation to 24-pulse from the input current standpoint. The system is fully analyzed taking into consideration the impedance mismatches and pre-existing voltage distortion in the utility. These inequalities are shown to result in unequal current sharing among the rectifiers. In order to improve performance and promote equal current sharing, the two diodes in the interphase transformer are replaced with SCR's.; In the third study, a new active interphase transformer (IPT) is introduced to draw high quality line currents ({dollar}<{dollar}1% THD) from the input utility. A current I{dollar}sb{lcub}rm x{rcub}{dollar} is injected into the secondary winding of the IPT to shape the input utility line current I{dollar}sb{lcub}rm a{rcub}.{dollar} The exact shape of I{dollar}sb{lcub}rm x{rcub}{dollar} is calculated mathematically and is shown to be near triangular in shape. A low kVA two switch PWM inverter is employed to inject a triangular shaped current I{dollar}sb{lcub}rm x{rcub}{dollar} in response to load condition. A US patent is pending on this approach and the technology has been licensed to a leading US power supply manufacturer.; All of the above approaches have been analyzed along with specific design examples to facilitate comparison. Finally, experimental results on a 208V, 10kVA laboratory proto-type and a 460V, 400kVA industrial proto-type are discussed.