2018 Volume 7 Issue 6 Pages 479-487
This paper proposes a novel multicellular ac-dc transformer (ADX). The proposed ADX consists of sensorless isolated ac-dc cell converters based on the multicellular converter topology and a non-isolated dc-dc converter for power factor correction (PFC). A single ac-dc cell converter is composed of a diode rectifier and a dc-dc transformer (DCX) with no feedback controllers. These cell converters are connected in input-series-and-output-parallel (ISOP) and input-parallel-and-output-series (IPOS) configurations to achieve various voltage transformation ratios. One of the features of the proposed ADX is the high scalability with no master-slave control. Each power converter in the ADX requires its own local information, and no additional auxiliaries are required for the global control of the multicellular converter, because the ISOP and the IPOS connection topologies in the multicellular converter inherently achieve balanced voltage and equalized current among the cell converters. The proposed ADX has a simplified control system and accomplishes high scalability without requiring additional components. A simplified circuit analysis is carried out to show the feasibility of the proposed ADX, and an ac 60V - dc 40V laboratory prototype, with three pairs of cell converters connected in ISOP, is fabricated to verify the analysis. The proposed approach contributes to realizing future dc distribution systems in data centers, taking into account the prevalence of the standardized high-power-density converters.
