SummaryIn battery energy storage system (BESS) applications, the life of the battery depends on the quality of the charging/discharging current. However, the dual active bridge (DAB) converter, which interfaces BESS with the DC link, suffers from a backflow current in all modulation schemes, degrading the battery's performance. Hence, this paper proposes a particle swarm optimization (PSO) based universal phase shift (UPS) modulation scheme to improve the battery's life. In the proposed modulation scheme, the phase shift ratio of DAB to eliminate the backflow power is estimated using PSO. Also, it is observed that there is an improvement in the zero voltage switching (ZVS) range of the DAB. Hence, the overall efficiency of the DAB converter is increased over a wide operating region. The operating principle of the proposed modulation scheme, steady state analysis of power transmission, and backflow power are reported in this paper. The theoretical performance of the proposed modulation scheme is validated in a 2 kW experimental setup.