UC Berkeley

On-board electric vehicle (EV) chargers convert grid ac voltage to dc voltage to charge a high-voltage battery pack. High efficiency and high power density single-phase ac-dc converters are desirable in such applications to reduce the heat loss, volume and weight of these chargers. Moreover, the capability of bidirectional conversion is preferred for potential vehicle-to-grid applications. This paper presents the system ar-chitecture and embedded digital control implementation of a 7 kW, universal ac (120-240 VAC) to 400 VDC single-phase ac-dc bidirectional converter. The converter features an interleaved 6-level flying capacitor multilevel (FCML) ac-dc stage and a series-stacked buffer for buffering twice-line frequency pulsating power to achieve high efficiency and power density. Test results that demonstrate both ac-dc power factor correction (PFC) and inverter operation at kilowatt levels are provided.