With the continuous expansion of off-grid hydrogen production,the inherent volatility of renewable energy generation poses substantial challenges to both the operational stability and economic viability of such systems.Here,we propose a capacity optimization method for an integrated energy system that incorporates both Alkaline Water Electrolyzer (AWE) and Proton Exchange Membrane Water Electrolyzer (PEM) under a decentralized and cooperative control framework.We adopt a double-layer optimal configuration model,and simultaneously consider multiple objectives including the typical daily operation cost,the annual investment and operation & maintenance costs,and the annual rate of renewable energy curtailment.This approach aims to achieve a rational and complementary configuration of electrolyzer modules,ultimately enhancing system economy,renewable energy utilization rate,and hydrogen production flexibility.Based on the optimal modular configuration,the system's economic performance is improved while the flexibility of hydrogen production is enhanced.Validation results demonstrate that the modularized coordination of the two electrolysers types,combined with electrical energy storage,effectively boosts the renewable energy consumption rate.Compared to the traditional centralized control strategy,the proposed method increases annual hydrogen sales revenue by 2.68% and total annual operating cost revenue by 91.67%,showing promising application potential.