A Bilevel Collaborative Planning Framework for Hydrogen Infrastructure Expansion in Offshore and Seaport Energy Systems

Collaborative planning is essential for managing conflict of interests between stakeholders, enabling coordinated decision-making, and ensuring efficient resource allocation. In the pursuit of decarbonization through hydrogen technology expansion, offshore wind power and offshore-produced green hydrogen trades create potential conflicts between offshore wind farm (OWF) owners and seaport power distribution network (PDN) operators, as they face competing interests in energy distribution, infrastructure investments, and market priorities. In the proposed collaborative planning process, the OWF owner, acting as the leader, determines the optimal sizing and deployment of hydrogen technologies to ensure profitability and maximize resource utilization. Meanwhile, the private seaport owner, as the follower, focuses on meeting hydrogen demand by deploying hydrogen technologies, optimizing operational efficiency, and reducing carbon emissions. A conflict arises as the OWF owner seeks to maximize profit by selling more power and hydrogen to the seaport, while the seaport owner aims to minimize operational costs by purchasing less from the OWF while ensuring grid stability. A bilevel collaborative planning model is introduced to formulate the Stackelberg game between the follower and the leader. Karush-Kuhn-Tucker (KKT) conditions are employed to convert the bilevel problem into its single-level counterpart. The binary investment decisions at the lower-level obstruct single-level formulation by violating KKT optimality conditions. To address this, a continuous reformulation of the lower-level problem is developed, ensuring compliance with KKT conditions. The proposed model is validated through three case studies, demonstrating its effectiveness in balancing stakeholder objectives, improving system collaboration, and supporting longterm sustainability goals.