Optimization design method of power distribution relationship for LLC-DAB hybrid bidirectional converter based on Sigma structure

The bidirectional isolated DC/DC converter is the key link inside the energy router, where the LLC-DAB hybrid bidirectional converter combines the advantages of LLC resonant converter and dual active bridges (DAB) converter, which are based on the Sigma architecture to achieve efficient power utilization, and a lot of research work has emerged in recent years. However, there are no specific criteria and guidelines for its proper power distribution relationship, which makes it difficult to optimize the overall system performance, and the existing methods are often optimized out of engineering experience or with a single objective. Therefore, this paper proposes a power distribution optimization design method based on a multi-objective particle swarm optimization (MO-PSO) algorithm for designing the optimal power distribution relationship between the converter sub-modules. Firstly, the particles boundary is obtained by realizing the soft switching conditions of all switching devices. Then, the loss breakdown is discussed in depth, and the dynamic model is obtained by using the reduced-order modeling method. With these as the optimization objectives, the optimal power distribution relationship and the corresponding optimal circuit parameters are obtained by using a MO-PSO algorithm. Finally, the proposed method is validated by a prototype and compared with the existing research work.