Fundamental Study on High-Power-Density Multicellular Bufferless Power Electronic Transformer

Abstract

An isolated multicellular ac-ac power electronic transformer (PET) is proposed to achieve a high-power-density and low-voltage industrial control transformer. The multicellular converter topology enables development of an ultrafast high-voltage power converter by utilizing high-frequency low-voltage isolated dc-dc converters. The fast response of the multicellular converter minimizes energy buffers, such as inductors and capacitors, and contributes toward the development of a compact and lightweight PET. A prototype of an AC 100V, 1.35kW multicellular PET was fabricated using nine 1.6MHz, DC 48V unregulated dc-dc converters connected in input-series-output-parallel input-parallel-output-series configuration, and the prototype achieved power densities of 4.50W/cm³ and 4.22W/g. Thus, a volume reduction of 1/14th and weight saving of 1/40th with respect to a commercial frequency transformer was verified.