An asymmetrical three-level dual-input bidirectional DC/AC converter with improved conversion efficiency for vehicle-to-grid application

An asymmetrical three-level dual-input (ATL-DI) bidirectional DC/AC converter is presented to interface a low voltage battery, a high voltage DC-bus and AC grid, simultaneously, for vehicle-to-grid (V2G) applications. A low voltage battery is employed as a new voltage level for the ATL-DI converter. Therefore, part of the battery power can be directly charged by or discharged into the grid, without processing by another bidirectional DC/DC converter. As a result, the power losses and power rating of the front-end DC/DC converter is reduced significantly, and the power conversion stages of the bidirectional DC/AC power conversion system are reduced to improve the overall conversion efficiency. Meanwhile, the three-level characteristic can help to reduce the switching losses and size/volume of the filter inductor of the ATL-DI DC/AC converter. Topology and operation principles of the ATL-DI bidirectional DC/AC converter are analyzed. A 2kW prototype is built and tested to verify the effectiveness and advantages of this method.