Dynamic control and dead-time compensation method of an isolated dual-active-bridge DC-DC converter

This paper presents dynamic control and a dead-time compensation method of an isolated dual-active-bridge (DAB) dc-dc converter. Conventional phase-shift control methods for the DAB converter may cause dc offsets in both inductor current and transformer magnetic flux density in transient states. The dynamic control method in this paper independently controls the diagonal switches in each H-bridge converter to modify the duty ratios in transient states. This method enables both inductor current and transformer magnetic flux density to be settled within a half switching period without any dc offsets. Moreover, the phase-shift error caused by the dead time is analyzed in terms of the switching angle. This analysis reveals that the dead time causes the switching-angle error in only one of the two H-bridge converters and may cause dc offsets. A new dead-time compensation method based on this analysis is proposed to eliminate the dc offsets and to achieve a good dynamic response. A 5-kW experimental system verifies the validity of the proposed control method.