Pulse doubling in zigzag–connected autotransformer–based 12–pulse ac–dc converter for power quality improvement

Abstract

This paper presents a pulse doubling technique in a 12-pulse ac-dc converter which supplies direct torque controlled motor drives (DTCIMDs) in order to have better power quality conditions at the point of common coupling. The proposed technique increases the number of rectification pulses without significant changes in the installations and yields in harmonic reduction in both ac and dc sides. The 12-pulse rectified output voltage is accomplished via two paralleled six-pulse acdc converters each of them consisting of three-phase diode bridge rectifiers. An autotransformer is designed to supply the rectifiers. 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. Independent operation of paralleled diode-bridge rectifiers, i.e. dc-ripple re-injection methodology, requires a Zero Sequence Blocking Transformer (ZSBT). Finally, a tapped interphase reactor is connected at the output of ZSBT to double the pulse numbers of output voltage up to 24 pulses. 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, 12-pulse, and proposed converters from view point of power quality indices. Results show that input current total harmonic distortion (THD) is less than 5% for the proposed topology at various loads.

Induction motor drive based on direct torque controlled used multi-pulse AC-DC rectifier

“…To this end, researchers have focused on solutions to eliminate current THD such as the use of multipulse rectifiers (MPRs). These MPRs are based on phase-shifting transformers or pulse doubling circuits [4][5][6][7]. However, under low source impedance or low load, the current THD for MPRs up to 20 pulses will be more than 5% [8][9][10][11][12][13][14].…”

Comparison of power quality indices and apparent power (kVA) ratings in different autotransformer-based 30-pulse AC–DC converters

“…For DTCIMD's one effective solution is to employ multipulse AC-DC converters. These converters are based on either phase multiplication or phase shifting or pulse doubling or a combination (Abdollahi, 2012h;Abdollahi & Jalilian, 2011, 2012bPaice, 1996;Singh, Bhuvaneswari, & Garg, 2007b). Although, in the conditions of light load or small source impedance, line current total harmonic distortion (THD) will be more than 5% for up to 18-pulse AC-DC converters (Singh, Bhuvaneswari, & http://dx.doi.org/10.1016/j.jart.2016.12.007 1665-6423/© 2017 Universidad Nacional Autónoma de México, Centro de Ciencias Aplicadas y Desarrollo Tecnológico.…”

“…A hexagonconnected autotransformer-based 20-pulse AC-DC converter is reported in (Abdollahi, 2012a) which has THD variation of 5.18-7.20% from full-load to light-load (20% of full-load). A zigzag-connected autotransformer-based 24-pulse AC-DC converter is reported in (Abdollahi, 2015a) which has THD variation of 3.95-5.85% from full-load to light-load (20% of full-load). Another T-connected autotransformer-based 24-pulse AC-DC converter has also been presented in Singh, Bhuvaneswari, and Garg (2006a), however, the THD of the supply current with this topology is reported to vary from 2.46% to 5.20% which is more than 5% when operating at light load.…”

Thirty-six pulse rectifier scheme based on zigzag auto-connected transformer

“…Abdollahi [22][23][24][25] proposed Scott, delta/polygon, polygon, and delta/hexagon connected autotransformer based 36-pulse AC-DC converters, which supplied induction motor drives to improve power quality at the PCC. Several rectifier systems based on autotransformer with double-tap or triple-tap changer were included in references [26][27][28][29]. The multitap changer utilized DC ripples reinjection technique, which could improve power quality criteria of the proposed converters without much alteration in the installations.…”