Autoconnected-Transformer-Based 20-Pulse AC–DC Converter for Telecommunication Power Supply

In this paper, an autoconnected-transformer-based 20-pulse ac-dc converter is proposed for harmonic current reduction in switched-mode power supplies (SMPSs) of moderate rating (10-15 kW). The proposed ac-dc converter is realized with a fractional magnetic rating of the load. The supply current is nearly sinusoidal with low total harmonic distortion, and the power factor is close to unity. A set of power quality indices at three-phase utility for an SMPS is presented for both 20- and 6-pulse converters to compare their performances. It is determined that the power quality indices at ac mains with a 20-pulse converter meet IEEE Standard 519 even at varying loads. A laboratory prototype of an autoconnected-transformer-based 20-pulse ac-dc converter has been designed and developed to validate the findings from simulation. Various tests have been conducted on it, and the test results conform to the simulation results.