Stability Analysis and Control Based on Discrete Model of Dual Active Bridge Converter

Dual active bridge (DAB) converters are widely used in power electronic systems and energy storage devices. However, due to the existence of semiconductor power switches, the converter is a typical strongly nonlinear, variable structure, discrete circuit system in essence. Some strange behaviors often occur when it works, such as some unknown electromagnetic noise, intermittent instability and sudden collapse of the system. In this paper, the nonlinear behavior of dual active bridge converter is studied. Firstly, based on the existing method of constructing discrete model, the discrete iterative model of DAB converter considering the sample and digital control delay is established. The relationship between the stability of the DAB converter and the parameters of the proportional controller is analyzed through the simulation comparison between the discrete iterative model and the traditional single phase shift control model. Finally, the stability boundary is accurately predicted by the phase trajectory diagram, and the bifurcation phenomenon is successfully suppressed by the parametric resonance perturbation method.