An optimal control for dual active bridge converter in battery charging applications

Abstract

Dual active bridge (DAB) converter is an ideal bidirectional DC/DC converter and serves as a core device for enabling bidirectional energy transfer in power router systems and energy storage units. In order to reduce power losses and battery damage during the charging process, a minimum current stress control scheme satisfying soft switching conditions is proposed. Additionally, a three-stage charging of the battery is achieved based on voltage and current dual-loop control. This article analyzes the working principles of the DAB converter using triple-phase-shift (TPS) modulation. By examining the switching modes and waveforms of the DAB converter under TPS modulation, the condition for achieving soft switching is determined. Furthermore, a combination of the Lagrange multiplier method (LMM) and the Karush-Kuhn-Tucker (KKT) algorithm is employed to ensure that the DAB converter operates under both soft switching and minimum current stress conditions. This approach simultaneously reduces both switching and conduction losses, thereby enhancing the charging efficiency of the battery. Finally, an experimental platform is established for validation, and the experimental results confirm the effectiveness of the proposed modulation strategy.