Transient DC Bias Suppression for Three-Level Dual-Active-Bridge Converter

Dual-active-bridge (DAB) dc–dc converter usually adopts phase-shifting control to control the power transmission of DAB converter. As the theoretical premise in the steady state analysis cannot be satisfied during the adjustment process of phase shift value updating, it leads to the generation of transient dc bias. To address the transient dc bias problem of the three-level DAB converter, a transient suppression strategy based on carrier symmetry update is proposed. The transient suppression is realized after half a cycle by adjusting the equivalent symmetrical midline position of the output voltage waveform for the three-level full-bridge side and using the equivalent decoupling suppression for the two-level full-bridge side. The strategy is equally applicable to single-phase-shifted, double-phase-shifted, and triple-phase-shifted modulation. The effectiveness of the strategy is verified by simulation. Finally, the proposed strategy is experimentally verified. By designing and building an experimental prototype, the effectiveness of the transient dc bias strategy is verified, which can effectively reduce the current overshoot and realize the transient dc bias suppression.