A Two-Stage Bidirectional DC–DC Converter With a Wide Output Voltage Range for DC Fast Charging Stations in E-Mobility Applications

The drive to reduce the charging time and energy loss in electric vehicles (EVs) has led to increasing battery voltages to 800 V, 1000 V, 1.25 kV, and 1.5 kV, posing new challenges for designing EV fast chargers, especially for heavy-duty EVs. Two-stage converters, comprising isolated and regulated dc-dc stages, are emerging for their superior performance. This article proposes a novel two-stage bidirectional dc-dc converter with an extremely wide operating voltage range. The design features a dual-transformer reconfigurable three-leg converter (DTR3LC) in the first stage, an interleaved reconfigurable buck converter (IRBC) in the second stage, and four auxiliary switches for reconfiguration. These switches enable the secondary side of the DTR3LC to switch between parallel and series connections, which are then regulated by the IRBC, resulting in high efficiency and low current ripple across a wide voltage range. A 1-kW scaled-down laboratory experimental setup was developed and tested with an input voltage of 80 V to charge EV batteries ranging from 15 to 150 V, achieving a maximum efficiency of 95.32% at 150 V.