Hybrid control strategy for DAB-LLC hybrid converter based on multi-objective optimization method

• Highlights 1: The application of the topology dynamic switching control to the DAB-LLC hybrid converter can increase the gain range of hybrid converter and reduce the voltage stress of the DAB module circuit. • Highlights 2: A constant frequency hybrid control strategy combining EPS control and topology dynamic switching is given, then the detailed analysis process of topology switching voltage in the strategy is given. • Highlights 3: The multi-objective particle swarm optimization algorithm (MO-PSO) is introduced. The efficiency loss and dynamic performance of the hybrid converter are taken as the optimization objectives to design the topology switching voltage, which achieves the good dynamic response based on ensuring high efficiency. To solve the application limitations of the DAB-LLC hybrid converter with Sigma structure in a wide range of input voltage, this paper presents a constant frequency hybrid control strategy. The strategy consists of two parts, one is to introduce topology dynamic switching control into the LLC module circuit in DCX (DC-DC) operation mode, which expands the voltage gain range. Second, by introducing extended phase shift (EPS) modulation into the DAB module circuit, achieving zero-voltage switching (ZVS) across the entire 0–100 % rated load range, and the effective value of the leakage inductor current is reduced. To determine the topology switching voltage of the LLC module circuit, a multi-objective optimization method is introduced to ensure that the hybrid converter has better dynamic responsiveness when achieving efficient energy transfer in wide input voltage range. Finally, the effectiveness of this approach was ultimately validated through an experimental prototype operating within an input range of 60 to160 V and delivering an output of 80 V. Efficiency improved by 2 % compared to traditional design methods.