A multi-objective sorting rotation control strategy for hydrogen production system considering electrolyzer degradation and state transition

In an off-grid hydrogen production system, complete dependence on fluctuating renewable energy may cause unbalanced switch action and operation time among multi-alkaline electrolyzers (AELs), which will worsen the AEL degradation and reduce the hydrogen production. To address this, we propose a novel multi-objective sorting rotation control strategy to equalize the AEL operation differences. In this strategy, we design two rules based on the Pareto fronts of AELs to arrange the AEL startup sequence before each rotation cycle. The control strategy balances the AEL wear based solely on their current status and real-time renewable power, thereby meeting the online control demand. Besides, we develop an AEL state transition model and strategy to describe the state transitions and their time delays. We also establish an AEL voltage degradation model considering the impact of start-stop actions and different operation conditions. Finally, in the case studies, three existing control strategies, simple start-stop, cycle rotation, and multi-objective weighted rolling control strategies, are compared with our method. In the daily operation, the standard deviation of AEL degradation of our strategy is reduced by 88 %, 66 %, and 82 % to the simple start-stop, cycle rotation, and multi-objective weighted rolling control strategies, respectively. In the yearly case, this value of our strategy achieves a reduction of 98 %, 78 %, and 74 % compared to the mentioned strategies, respectively. These demonstrate that our strategy can effectively equalize the wear of AELs. The maximum voltage increases of our strategy are 539.5 μV and 0.0641 V in daily and yearly operations, which are lower than other strategies, thus avoiding AEL over-degradation. Furthermore, comprehensive sensitivity analyses validate the adaptability and robustness of our strategy.