A Control Method to Reduce Overshoots in High-Frequency Link Current and Voltages at Load Transients of a Dual-Active-Bridge Series-Resonant Converter

A dual-active-bridge (DAB) series-resonant converter is well researched in the literature to find out a suitable pulsewidth modulation (PWM) technique that can achieve voltage regulation, zero-voltage switching, and minimum root-mean-square current in the high-frequency (HF) link. Although the advanced PWM techniques achieve desired performance at steady state, the HF link current and voltages suffer from huge overshoots during load transients, which can damage semiconductor devices and can cause the saturation of the high-frequency transformer. Therefore, in this article, a relationship between the pole positions and the percentage overshoot is derived, so that any design with the tradeoff between fast dynamics and overshoot can be done analytically. As the system involves multiple state and input variables, which are also closely coupled, a multivariable state-feedback controller design is proposed to control the dynamics of all the HF link state variables simultaneously. In any DAB-based topology, the peak volt-ampere rating of the passive components can increase by 80% due to these overshoots. The proposed control successfully restricts the overshoots below 25% with a settling time of 5 ms for the output voltage. The experimental verification is carried out in a 2.25-kW hardware prototype.