Optimal asymmetric extended-phase-shift modulation scheme for single-stage bidirectional totem-pole dual active bridge AC-DC converter

Single-phase single-stage AC–DC converters are widely applied, especially in on-board chargers (OBCs) requiring high efficiency, high power density, and bidirectional operations. The full-bridge totem-pole dual-active-bridge topology offers promising prospects due to its compact integration and simplified control. However, conventional phase-shift modulation schemes fail to fully harness its potential and overlook the impact of initial inductor current coupling on grid current quality, control accuracy, and overall efficiency. This paper proposes an optimized asymmetric extended phase-shift (AEPS) modulation scheme, which constrains the initial inductor current under traditional open-loop natural power factor correction (NPFC) requirements. The proposed scheme decouples initial inductor currents across adjacent switching cycles while minimizing peakto-peak current through a multi-objective optimization approach. As a result, both converter efficiency and grid current quality are significantly improved. Experimental validation on an 800 W prototype confirms the effectiveness and feasibility of the proposed scheme. Under 350V DC voltage and full-load condition, the proposed scheme notably enhances grid current performance and achieves peak efficiency improvements of 5.38%, 1.85%, and 0.78% in forward operation, and 5.57%, 1.89%, and 0.77% in reverse operation, compared to conventional SPS, EPS, and TPS schemes, respectively.