Nonlinear dynamics-based control strategy for hydrogen-based sustainable energy grid with flexible load of P2H system

In off-grid DC hydrogen production systems, photovoltaic (PV) variability often leads to source-load mismatches, resulting in excessive proton exchange membrane electrolyzer (PEMEL) input current ripple and compromising hydrogen production safety. While PEMEL’s flexible load characteristics can stabilize operations by tracking PV fluctuations, the nonlinear dynamics and time-delay effects of the PEMEL branch coupled with an input-series output-parallel dual active bridge (ISOP-DAB) converter present significant control challenges. Unconstrained voltage ratios in triple-phase-shift (TPS) modulation exacerbate PEMEL-ISOP-DAB equivalent load-PV mismatch. Thus, we propose an extended state observer (ESO)-based flexible load active disturbance rejection control (ADRC) strategy, which employs a three-tier control framework. The first tier ensures power balance across converter submodules through voltage sharing control. The second tier minimizes converter current stress using a Lagrange multiplier optimization algorithm. The third tier implements an ESO-based terminal sliding mode control (TSMC) strategy to dynamically adjust the electrolyzer’s equivalent load and match PV output, thereby reducing electrolyzer input current ripple. Compared to conventional PI control, the strategy reduces steady-state current ripple by 84.66 % and step-change-induced ripple by 97.36 %, enhancing PEMEL safety without requiring complex hardware modifications. Its hierarchical control framework can be directly integrated into existing photovoltaic-hydrogen systems to enhance operational safety and hydrogen yield.