Dead-Time Compensation with DC Offset Current Elimination Method Using Three-Level Operation for Dual Active Bridge DC-DC Converter

This paper proposes a compensation method of a non-linear transmission power error caused by a dead-time for a dual active bridge (DAB) converter with a three-level operation. This power error is compensated by the zero-current period longer than the dead-time in three-level mode. In addition, the mode change sequence between the two-level and the three-level is also proposed to suppress a dc offsets on the transformer current. The validity of the proposed method is confirmed by a 2.5-kW prototype. As the experimental results, the transmission-power error is reduced by 80.7%. In addition, the peak value of the magnetizing current at the transient state is reduced by 56% because the dc offset is eliminated. Moreover, the mode changing is achieved within two switching periods.