Abstract: Dual active bridge（DAB） DC/DC converters have a variety of modulation schemes. With triple phase shift（TPS） modulation, there are three control variables that can help to achieve good flexibility. In this paper, by analyzing the switching modes and the operating waveforms of the DAB converter under the TPS modulation, the constraint conditions in which each switch device can realize ZVS under different operating modes were derived, the feasible control regions of All-ZVS could be further deduced. On this basis, with the existing inductor current RMS optimization control algorithm, a quasi-optimal current RMS control strategy with achieving All-ZVS was proposed. It can be concluded that not only the switching condition of all the switches is improved, but also the switching losses and conduction losses are reduced. Hence, the conversion efficiency is improved. The switching frequency can be increased with the proposed method and consequently. The power density can be improved. Finally, a prototype of DAB was built, and the experimental results verified the effectiveness of the proposed modulation scheme.