Optimal Capacity Configuration of a Reversible Solid Oxide Cell-Integrated Electricity–Heat–Hydrogen Energy System Balancing Economic Performance and Renewable Energy Accommodation

To enhance renewable energy accommodation and operational flexibility under high renewable energy penetration, this study proposes a multi-objective optimal capacity configuration method for an electricity–heat–hydrogen integrated energy system incorporating a reversible solid oxide cell (RSOC). First, considering the bidirectional electricity–hydrogen conversion capability and waste heat recovery of the RSOC, an electricity–heat–hydrogen multi-energy complementary system is constructed, and efficiency correction models are established for key energy conversion devices to characterize their part-load characteristics. Second, representative source–load scenarios are generated using Latin hypercube sampling and K-means clustering, and a multi-objective optimal capacity configuration model is formulated to minimize the annualized total cost and the wind and photovoltaic power curtailment rate. Finally, given the limitations of the non-dominated sorting genetic algorithm II (NSGA-II) in complex capacity configuration problems, such as premature convergence to local optima and insufficient population diversity, an adaptive crossover and mutation mechanism, a local search strategy, and a dynamic selection mechanism based on comprehensive crowding distance are introduced to improve its optimization performance. A balanced configuration scheme is then selected based on the knee point of the Pareto front obtained by the algorithm. Case-study results show that the Pareto solution set obtained by the improved NSGA-II (INSGA-II) has better overall quality than those obtained by NSGA-II and multi-objective particle swarm optimization (MOPSO). The resulting balanced configuration scheme has an annualized total cost of CNY 422.9 million and a wind and photovoltaic curtailment rate of 2.797%. The proposed method effectively coordinates system economic performance and renewable energy accommodation, enhances the coordinated utilization of electricity, heat, and hydrogen energy flows, and provides a reference for capacity planning of integrated energy systems under high renewable energy penetration.