Determination of the optimal sub-mode for bidirectional dual-active-bridge DC-DC converter with multi-phase-shift control

Multi-phase-shift control (MPS) including triple-phase-shift (TPS) and dual-phase-shift (DPS) can achieve high efficiency in a wide operating power range for isolated bidirectional dual-active-bridge (DAB) dc-dc converters. However, considering that multi possible sub-modes corresponds to various phase-shift combinations for the same amount of output power, the optimal sub-mode requires to be primarily determined. In this paper, a method to determine the optimal sub-mode by key waveform features is proposed and verified by the comprehensive trade-off results of reactive power, the inductor peak current and inductor rms current experimentally. Furthermore, the effect of non-ideal electrical parameters including parasitic resistance, the voltage drop of MOSFETs, and dead time are analysed in the comparison of the complete output power plane with MPS control. Main discrepancies especially the loss of the maximum deliverable power are described and explained. Experimental evaluation shows the effectiveness of the proposed method in determining the optimal sub-mode with MPS control.