Cross-scale coordinated optimization method for electricity-thermal-hydrogen systems in chemical industrial parks based on long-term and short-term flexibility margin evaluation

Chemical industrial parks are rapidly developing integrated electricity-thermal-hydrogen supply systems based on green electricity and pervasive hydrogen. Yet unexpected events, renewable fluctuations, and market disturbances create major challenges for real-time supply-demand matching. This study proposes a cross-scale coordinated optimization method spanning seconds, minutes, and hours, capturing asymmetric ramping dynamics. A dynamic adjustable margin index is proposed to quantify regulation capability across timescales and support balanced short-term and long-term scheduling. By linking equipment-level dynamics to system-level performance, the proposed approach establishes a methodological foundation for coordinated operation under high renewable penetration. Case studies demonstrate that the proposed method ensures the accuracy of automatic generation control load tracking while significantly improving system economic efficiency and operational flexibility. The system achieves upward regulation margins of 680.45, 617.67, and 705.61 MW for short, medium, and long horizons, highlighting the influence of the optimization horizon on regulation capacity. Enhancing gas turbine ramping or adding hydrogen storage further increases system benefits by 1.36 % and 5.02 %, respectively. Compared with conventional methods, the proposed approach guarantees strict feasibility with higher computational efficiency, demonstrating strong engineering practicality.