Effect of Phase Shift Definition on Power Characterization of Isolated DC–DC Converter Under PWM Plus Phase Shift Modulation

Abstract

PWM plus phase shift (PPS) modulation is a popular modulation technique for the current fed dual active bridge (CFDAB) converter. Power transfer characteristics for any modulation technique are important for converters. However, in the literature, different power characteristics of CFDAB are presented for PPS modulation. This disparity in power transfer behavior creates confusion and ambiguity to the readers. This brief reveals the reason for such disparity. This is primarily due to the definition of the phase shift considered. When the phase shift is considered between the rising edges of high frequency voltages, asymmetric power transfer characteristics are obtained. On the contrary, symmetric power transfer characteristics are obtained if phase shift is considered between the mid point of high level of high frequency voltage signals. Thus the latter provides useful features and universal conditions for power reversal and peak power transmission individually. Steady state power under different modulation is obtained from unified model of CFDAB. The analytical results and experimental investigations are in agreement with each other.