Bidirectional MHz-switching Multi-cell Converter for Low-voltage Bufferless Power Electronic Transformer (BLPET)

Multicellular buffer-less power electronic transformer (BLPET) has been newly proposed to develop high power density industrial control transformers. The bidirectional and unregulated isolated dc-dc converters of over 1 MHz switching frequency are utilized for the cell converters, and the cell converters are stacked based on the ISOP (Input Series Output Parallel) -IPOS (Input Parallel Output Series) connection topology to realize higher voltage multi-cell PET operated at over 1 MHz switching frequency. The high frequency multi-cell PET enables to reverse the power flow derived from the reactive load instantaneously without the large energy buffer capacitors. An ac 100 V-ac 100 V, 1.35 kVA multi-cell BLPET has been fabricated, and the successful circuit operation under the inductive load condition with the power factor of 0.7 has been verified experimentally. The proposed approach has also demonstrated the potential to realize the volume reduction of 1/14 and the weight saving of 1/40 compared with the commercially available ac 100 V line frequency transformer.