Identifying the ecological operating space for explicit decisions of hydro–hydrogen–wind–photovoltaic hybrid power systems

Balancing energy efficiency and ecological sustainability is a critical challenge for hybrid power systems. Previous studies have primarily employed operation models to derive decisions that meet ecological requirements. However, the explicit relationship between ecological benefits and operation decisions remains underexplored. This study establishes an ecological operating space that explicitly quantifies the interaction between ecological benefits and operation decisions for hydro–hydrogen–wind–photovoltaic hybrid power systems. Initially, the ecological alteration degree is quantified based on ecological flow constraints. Subsequently, a multi-objective model is developed for optimizing operation revenue and assurance rate across varying degrees of ecological alteration. Finally, the ecological operating space is derived using a combined approach of the inflection point method and implicit stochastic optimization. A case study of China's Ertan hydro–hydrogen–wind–photovoltaic system demonstrates that ecological alteration has a negative correlation with the assurance rate. The ecological operating space improves operation revenue to 4.33 billion CNY (+12.18 %) while simultaneously elevating the assurance rate to 100 % (+11.96 %), compared with conventional operating rule curves. Moreover, the ecological alteration degree is decreased from 0.08 to 0.02 (−75.00 %). These findings demonstrate that the proposed ecological operating space offers an effective solution for improving the economic performance, reliability, and environmental sustainability of hybrid operation.