Natural Boundary Transition and Inherent Dynamic Control of a Hybrid-Mode-Modulated Dual-Active-Bridge Converter

This article proposes a hybrid-mode modulation strategy for the single-phase dual-active-bridge (DAB) dc–dc converter that realizes soft switching in the whole operating range. Different from existing modulation methods that are usually dependent on complex mathematical optimization processes, the presented article reveals that the simple trapezoidal continuous conduction mode and triangular discontinuous conduction mode inspired by a quasi-single-active-bridge operation can naturally and sequentially extend the soft-switching boundary of the conventional single-phase-shift (SPS) modulation to the full range in both the buck and boost modes. Meanwhile, the transformer rms current is also reduced. Moreover, a fast-dynamic control with inherent seamless mode transitions is realized by introducing the predictive-current SPS modulation. The proposed hybrid-mode modulation strategy with closed-form solutions can be easily implemented in a generalized closed-loop controller, which enables an ultrawide-voltage-range operation of the DAB converter with significantly elevated efficiency and fast transient responses. The effectiveness of the proposed method is validated by comprehensive experimental results from a small-scale DAB prototype.