P ^DCT-Partial-Power Pre-Regulated DC Transformer

• Published in: IEEE transactions on power electronics 2019-07, Vol.34 (7), p.6036-6047
• Main Authors: Neumayr, Dominik, Vohringer, Matthias, Chrysogelos, Nikolaos, Deboy, Gerald, Kolar, Johann W.
• Format: Article
• Language: English
• Subjects: Auxiliary converter; Converters; dc transformer (DCT); Density measurement; Electric potential; Electromagnetic compatibility; Electronics; Energy conversion efficiency; Feedback control; Filter design (mathematics); Frequency control; partial-power (PP) converter; Power system measurements; pre-regulation; Process control; Reactive power; Resonant converters; series-resonant LLC converter; Topology; Transformers; Voltage control; Windings
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2018.2879064

In this paper, a new approach to regulate the output voltage of a resonant, constant voltage transfer ratio 380 V/48 V isolated dc-dc converter is presented. Rather than applying variable frequency control to the resonant converter, which would result in reactive power processing and a more complicated electromagnetic compatibility filter design, the converter remains in its optimal operating point all time and an additional partial-power (PP) processing auxiliary converter is used to tightly regulate the output voltage. The PP converter, supplied through a tertiary winding of the resonant converter's transformer, regulates the output by adding or subtracting voltage from the dc input and has only a marginal impact on the overall efficiency of the dc-dc converter. The principal of operation is explained in detail including Sankey diagrams to illustrate the power processing of the converter and a feedback control system is proposed to tightly regulate the 48 V output voltage. A hardware demonstrator rated at 1.5 kW is implemented to cope with input voltage variations between 340 and 420 V and experimental results are provided showing that the output voltage can be kept within \pm {1}{\%} of the nominal 48 V even under harsh input voltage and load transients. The realized dc-dc converter with PP pre-regulation features an overall efficiency of 97.7\% at rated power and a power density of 8.6 kWdm^{-3} (141w/^{3} in).