Decomposed Discrete-Time Model and Multiscale Oscillations Analysis of the DAB Converter

A decomposed discrete-time model of the dual active bridge (DAB) converter is proposed in this article, which has significantly simplified the conventional discrete-time model without affecting the calculation accuracy of the exponential matrix. Therefore, the decomposed discrete-time model is also applied to the design of the digital controller to compensate the digital control delay, which could deteriorate the stability of the system. Besides, the comprehensive and systematic analysis of all the possible unstable phenomena of the DAB converter is conducted to reveal their intrinsic mechanism. The corresponding multiscale oscillations and the sudden jump phenomena are also presented to exhibit their dynamic characteristics. In addition, the closed-form expressions of the state variables are obtained, which are utilized to explicitly express the analytical relationships among the state variables, system parameters, and the Floquet multipliers. Accordingly, the parameter spaces of the selected crucial system parameters are obtained, which can provide the guidance for the parameters design of the DAB converter.