Abstract: The fixed-parameter control method of dual-active-bridge（DAB） converter controlled by TPS scheme cannot adapt to the wide input voltage range, and the mismatch of converter parameter leads to the increase of inductor current. To solve this problem, this paper proposed a variable parameter control strategy to minimize root-mean-square（RMS） value of the inductor current. By dividing the mode and analyzing the power characteristics and soft switching characteristics in each mode, the unified optimal relationship between the control variables in the full range of the equivalent voltage ratio is derived. The control strategy calculates the equivalent voltage ratio in real time, then uses the unified optimal relationship to update the control variables in real time, so that the converter parameters are always matched, the RMS value of the inductor current is the smallest, and all switches can realize soft switching in the full power range. Finally, a 15 k W DAB converter experimental platform based on SiC devices was established. The experimental results verified that the proposed control strategy meets the control target of minimum current RMS value within the double input voltage range. The efficiency reaches more than 95% in the wide range and the highest efficiency is 97.4%.