Autotransformer Analysis based on 24 Pulse AC-DC Converters

摘要

The pulse doubling 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 ac-dc converters each of them consisting of three-phase diode bridge rectifiers. Different autotransformers are designed to supply the rectifiers. But 12-pulse configurations fail to comply with limits of total harmonic distortion (THD) of supply current to be less than 8% specified in the IEEE Standard 519 [3]. Increasing the number of pulses further results in improvement in various power-quality indexes but along with the additional cost of different converters and increased system complexity. To improve the THD of ac-mains current at a reduced cost, pulse doubling technique has been observed to be a viable and cost-effective solution. This study, based on technical and economic factors, compares different autotransformer based 24 pulse AC-DC Converters employing a pulse doubling technique. In this paper, the comparison of tapped delta, polygon and T connected autotransformer based 24-pulse AC-DC converters has been presented. These converters has been implemented and simulation using Matlab/Simulink software for similar ratings under different load conditions. A set of power-quality indices on input ac mains and on a dc bus for a DTCIMD fed from different 24-pulse ac-dc converters is given to compare their performance. Economic comparison of 24 pulse ac–dc converters is based on the apparent power (kVA) ratings of the different autotransformer for 24 pulse AC-DC Converters.