Using Sampled-Data Modeling Method to Derive Equivalent Circuit and Linearized Control Method for Dual-Active-Bridge Converter

In this paper, based on sampled-data modeling technique, a second-order equivalent circuit that can describe the global dynamic characteristics of dual active bridge (DAB) converter is developed. The proposed technique can characterize the dynamics of the ac current through the transformer and the output voltage. Afterwards, by using a sensitive-based tool, named participation factor, it is identified which state variables are critical for system stability and which state variables provide negligible effects. On this basis, the large-signal equivalent circuit is simplified, meanwhile the parasitic resistance is still taken into account by an intuitive "loss branch". This model can be used to comprehensively investigate the relationship of the DAB converter stability versus circuit parameters, controller gain, input/reference voltage, and the load conditions, and these results can be expressed analytically. Furthermore, a linearized control method is proposed to eliminate the nonlinear terms in the equivalent circuit model. It facilitates to reduce the sensitivity of system stability to the load condition and reference voltage and helps to enlarge the stable region. Finally, the proposed model is validated by comparing the results obtained by the model with the simulations and experimental results. The effectiveness of the linearized control method is also demonstrated.