| Abstract |
This paper proposes the least possible transformer rms current control strategy to operate an isolated dual active bridge (DAB) dc-dc converter using dual phase-shift (DPS) control. Close-form expressions of converter parameters e.g. average and rms current, active and apparent power are derived for four possible operating modes under DPS control. Thereby, the Lagrangian objective function is formulated such that apparent power and hence reactive power are truly minimized for the desired active power transfer. As output power is varied, optimal phase-shift ratios are deduced numerically, which constitute the minimum rms current trajectory. It is subtly utilized to devise a closed-loop controller, which employs feedforward control and obviates the use of a lookup-table-based approach, requiring off-line precomputation of optimal duty ratios. In addition, necessary boundary conditions are also derived to ensures fully \acrfull{zvs} operation in both active H-bridges of DAB converter. A 4.0 kW, 400/400 V, 25 kHz, isolated DAB converter is simulated in MATLAB/ Simulink. At rated output power, a maximum Q/P ratio of 1.158 and a minimum efficiency of 98.77\% are noted. It corroborates that the proposed minimum rms current control strategy works well for DPS control of DAB converter. |
