A Generic Transient DC Bias Elimination Method for Dual- and Triple-Active Bridge Converters

Conventional single-phase-shift (SPS) modulation developed for dual-active bridge (DAB) converters can induce a significant DC bias current during transient due to the abrupt update of the phase-shift angle. This DC component in the transformer’s AC current may result in serious saturation of the magnetic components. Though many modulation strategies have been proposed for DAB converters, the DC bias current during the transient cycle can only be reduced but not fully eliminated. In this work, an intermediate phase-shift (IPS) modulation method is proposed to effectively eliminate the DC bias current during the transient cycle without scarifying simplicity. The proposed method is generic, which can be applied not only to the DAB, but also the multi-port DC-DC converters, such as a triple-active bridge (TAB) converter. Both theoretical analysis and experimental studies for DAB and TAB are presented to validate the effectiveness of the proposed method.