Modeling with Beat Frequency Dynamics and Phase-Frequency Control Design for a Dual-Bridge Series Resonant Converter

Phase-frequency modulation is an effective soft-switching technique for a dual-bridge series resonant converter (DBSRC). In the literature, the DBSRC topology is investigated with phase-frequency control to increase the soft-switching region and to reduce the reactive power circulation in the high-frequency link. However, behavior of the circuit during transient was not addressed, especially when multiple input variables are involved. This article proposes a small-signal model for the DBSRC considering phase shift and switching frequency as the control parameters. The proposed model studies the dependence of the control variables. Therefore, a compensator design is proposed, which helps the two control loops to operate independently. Transient response of the DBSRC is extensively studied by providing a step load and a step change in output voltage reference. Proposed modeling accurately predicts the transient behavior of the circuit. The beat-frequency phenomenon, which is often found in resonant converters, can also be predicted in this model. The design of resonant tank parameters is also addressed in this article. Finally, the proposed model and the control method are verified in a 2.7 kW hardware prototype.