An Interleaved 6-Level GaN Bidirectional Converter With an Active Energy Buffer for Level II Electric Vehicle Charging

On-board electric vehicle (EV) chargers provide ac to dc conversion capability to charge a high-voltage battery pack. As they are carried within a vehicle at all times, high efficiency and high power density are desirable traits for such a converter, in order to reduce the size, weight, and power loss of the system. Bidirectional capability is also desirable for an onboard charger to support vehicle-to-grid ancillary applications. This paper presents the implementation of a bidirectional single-phase ac-dc converter, converting between universal ac (120-240 VAC) and 400 VDC. Discussions of system architecture, control, mechanical design and assembly, and thermal management of an interleaved 6-level flying capacitor multilevel (FCML) power factor correction (PFC) stage with a twice-line-frequency series-stacked buffer (SSB) stage are included. Experimental results demonstrating dc-ac inverter operations at the kilowatt scale are provided. A peak efficiency exceeding 99% is observed, and a maximum power of 6.1 kW is tested.