Review of Analysis Methods and Control Technologies for CLLC Resonant Converters

A CLLC converter is a high-frequency, high-efficiency, isolated bidirectional DC/DC converter that is widely used in DC microgrid applications. The typical topology and basic working principle of CLLC converters are introduced herein. Subsequently, both analysis methods and control technologies are reviewed. On the one hand, several steady-state analysis models are listed, consisting of a harmonic approximation-based model in the frequency domain and a state equation-based model in the time domain, and some initial dynamic models are also included. On the other hand, numerous new control technologies are presented for different targets, such as soft startup control methods from a safety perspective, synchronous rectification (SR) control methods for efficiency optimization, highly dynamic control methods for better performance, bidirectional switching control methods, and wide voltage gain control methods aimed at popular vehicle-to-grid (V2G) and electric vehicle (EV) charging application scenarios. Finally, the future evolution of CLLC resonant converters is discussed.