Transformer-flux-balancing control in isolated bidirectional DC-DC converters

The paper presents novel transformer-flux-balancing control methods for the isolated bidirectional full-bridge (FB) converter with active clamp and the bidirectional dual-active bridge (DAB) converter. Both approaches are based on the sensing and control of the transformer magnetizing current. For the isolated bidirectional FB converter the magnetizing current is obtained by sensing a single current, whereas for the DAB converter, both primary and secondary currents of the transformer need to be sensed to obtain the magnetizing current. Since in the DAB converter the magnetizing-current control can lead to excessive dc values of the winding currents, an additional control loop that eliminates the dc value of the primary and secondary currents is introduced. Performance of the proposed flux-balancing control for the isolated bidirectional FB converter was experimentally evaluated on a 2-kW prototype.