Research on the dynamic energy conversion and transmission model of renewable energy DC off-grid hydrogen system

The dynamic response characteristics between the multiple energy flows of electricity-hydrogen-heat in the renewable energy DC off-grid hydrogen production system are highly coupled and nonlinear, which leads to the complexity of its energy conversion and transmission law. This study proposes a model to describe the dynamic nonlinear energy conversion and transmission laws specific to such systems. The model develops a nonlinear admittance framework and a conversion characteristic matrix for multi-heterogeneous energy flow subsystems, based on the operational characteristics of each subsystem within the DC off-grid hydrogen production system. Building upon this foundation, an energy hub model for the hydrogen production system is established, yielding the electrical, thermal, and hydrogen energy outputs along with their respective conversion efficiencies for each subsystem. By discretizing time, the energy flow at each time node within the hydrogen production system is computed, revealing the system’s dynamic energy transfer patterns. Experiments were conducted using measured wind speed and irradiance data from a specific location in eastern China. Results from selected typical days were analyzed and discussed, revealing that subsystem characteristics exhibit nonlinear variation patterns. This highlights the limitations of traditional models in accurately capturing these dynamics. Finally, a simulation platform incorporating practical control methods was constructed to validate the model’s accuracy. Validation results demonstrate that the model possesses high accuracy, providing a solid theoretical foundation for further in-depth analysis of DC off-grid hydrogen production systems.