Multi-Dimensional Dynamic Performance Comparison of Hybrid Energy Storage Topologies for Off-Grid Flexible Hydrogen Production Based on System-Level Thermodynamic Dynamic Modeling of AEM Electrolyzers

To address the safety concerns in off-grid wind–solar hydrogen production systems, where fluctuating renewable power input can induce transient current shocks to the anion-exchange membrane (AEM) electrolyzer and exacerbate hydrogen–oxygen crossover under high-pressure operation, this paper develops a system-level simulation model of the AEM electrolyzer hydrogen production system based on system-level thermodynamic dynamic modeling. Three energy storage topologies—single supercapacitor, flywheel–battery hybrid, and supercapacitor–battery hybrid—are selected for comparative simulation studies. The regulation performance of each scheme is comprehensively evaluated using metrics including DC bus voltage stability, electrolyzer current slew rate (di/dt), anode–cathode pressure difference, and hydrogen content in oxygen (HTO) at a hydrogen-side pressure of 3 MPa. The results indicate that the single supercapacitor scheme, limited by its energy capacity, fails to maintain bus voltage stability in the later stage, with HTO rising from approximately 13,375 ppm to 13,405 ppm under 3 MPa, while in the pressure-effect tests HTO increases from 1900 ppm to 13,375 ppm as the hydrogen-side gauge pressure rises from 65 kPa to 3 MPa. Both the flywheel–battery and supercapacitor–battery schemes maintain the DC bus voltage within the 690–710 V range and keep HTO concentration stable under high-pressure conditions. Among them, the supercapacitor–battery topology exhibits the lowest current slew rate and the best transient impact suppression performance.