T-Connected Autotransformer Based 36-Pulse AC-DC Converter for Power Quality Improvement

This paper presents the design and analysis of a T-Connected autotransformer based 36-pulse ac-dc converter which supplies direct torque controlled induction motor drives (DTCIMD’s) in order to have better power quality conditions at the point of common coupling. The proposed converter output voltage is accomplished via two paralleled 18-pulse ac-dc converters. An autotransformer is designed to supply the rectifiers. The T-connected autotransformer makes use of only two single-phase transformers, resulting in savings in space, volume, weight, and, finally, the cost of the drive. The design procedure of magnetics is in a way such that makes it suitable for retrofit applications where a six-pulse diode bridge rectifier is being utilized. The aforementioned structure improves power quality criteria at ac mains and makes them consistent with the IEEE-519 standard requirements for varying loads. Furthermore, near unity power factor is obtained for a wide range of DTCIMD operation. A comparison is made between 6-pulse and proposed converters from view point of power quality indices. Results show that input current total harmonic distortion (THD) is less than 4% for the proposed topology at variable loads. Streszczenie. W pracy zaprezentowano projekt i analizę 36-pulsowego przekształtnika AD-DC bazującego na autotransformatorze typu T i zasilającego bezpośrednio silnik indukcyjny ze sterowanym momentem obrotowym DTCIMD. Układ wykorzystuje tylko dwa jednofazowe transformatory. Układ zapewnia odpowiednią jakość energii zgodnie z normą IEEE-519. Porównano układ z układem 6-pulsowym. (36-pulsowy przekształtnik AS-DC z autotransformatorem typu T)