Universal Control Scheme to Achieve Seamless Dynamic Transition of Dual-Active-Bridge Converters Using Zero-Current-Prediction

This article proposes a zero-current-prediction based digital control scheme to achieve the seamless dynamic transition of dual-active-bridge (DAB) converters. Compared with existing methods, only an extra variable between the master pulsewidth modulation and the sawtooth carrier is introduced. This extra variable is only determined by the voltage conversion ratio and the change of the existing phase shifts between master and slave legs. It accurately predicts the zero crossings of the inductor current and tunes it with the end of the carrier period. When the output power varies, the controller updates the digital registers at the beginning of the new carrier period, when the inductor current is zero. Thus, a seamless dynamic transition is achieved with zero dc bias current. This proposed digital control scheme is universally valid for the mainstream modulation methods of a single DAB converter. Moreover, it is adaptive to any load conditions, regardless of the zero-voltage-switching conditions and power flow directions. A hardware prototype is designed, tested, and compared with the conventional control method. The experimental results well validate the advantages of the proposed concept.