DC–DC converters are employed as essential energy conversion interfaces for the regulation of bidirectional power flow in off-grid hydrogen production systems. However, since the nonlinear characteristics and multi-timescale interactions of the converter, it is difficult to improve the efficiency of hydrogen production. To address this issue, a discrete-time modeling and stability analysis of the dual active bridge converter in off-grid hydrogen production systems is investigated in this paper. First, a bilinear discrete-time iterative model is constructed, which can integrate the photovoltaic, wind, battery storage, and electrolyzer subsystems interconnected. Then, the model is formulated to represent the nonlinear switching behavior of the converter for accurate prediction of the stability boundaries. Second, a bifurcation and eigenvalue analysis is conducted to characterize the nonlinear dynamic responses of each subsystem. Bifurcation diagrams and eigenvalue trajectories reveal the coupling effects among control gains, eigenvalue migration, and subsystem stability. These key indicators collectively determine the overall dynamic behavior of the system. Third, the proposed framework is validated through time-domain simulations and topological dynamic analyses. Then, the bifurcation of the inductor current is demonstrated to serve as an indicator for identifying the critical stability region, exerting a direct impact on both DC bus voltage regulation and hydrogen. Finally, the identified stability boundary and critical regions are used to adjust converter parameters and to optimize operations in renewable hydrogen production.
Kang et al. (Sun,) studied this question.