Downside-risk pre-positioning for resilient scheduling of an off-grid deep-offshore electricity-hydrogen integrated energy system under extreme weather

An off-grid deep-offshore electricity-hydrogen integrated energy system (DOEH-IES) provides a practical carrier for onsite offshore wind utilization and multi-energy coordination. However, under typhoon conditions, coupled wind-wave effects and platform motion reduce the available power of floating offshore wind turbines (FOWTs), introducing a time-varying downside risk that conventional scheduling methods often fail to mitigate proactively. To address this issue, a downside-risk pre-positioning framework is developed for the DOEH-IES that converts physical FOWT power reductions into actionable scheduling decisions. First, a wind power correction model for FOWTs is established by considering wave, floating-platform motion, and air density variation. A dynamically asymmetric envelope is then constructed to extract the time-varying downside exposure during a typhoon and further develop a downside risk indicator. Subsequently, driven by the risk indicator, BESS capacity is reserved in advance of the onset of high-risk periods. Case studies based on typhoon reanalysis data from the South China Sea show that the proposed dynamic asymmetric envelope achieves risk-oriented boundary characterization without increasing weekly average envelope conservatism, with a pre-typhoon average envelope width of 2.69 MW and a maximum downside deviation of 150 MW during peak disturbance. Relative to the comparison case without risk-informed pre-positioning, the proposed framework eliminates electrical load shedding and reserve insufficiency, increases pre-disturbance available stored energy by 72.5%, and reduces natural gas consumption by 15.0% with only a 2.09% cost increase. These results demonstrate that the proposed framework can effectively translate the risk into pre-positioning actions, safeguarding supply and equipment continuity.