Methodologies for assessing the needed flexibility

This paper presents a structured review of methodologies for assessing the flexibility needs of modern power systems, with a focus on both transmission and distribution levels. Flexibility is analyzed as a system-wide requirement to accommodate the variability and uncertainty introduced by renewable generation, and as a resource-side or grid-side capability enabled by controllable assets. The study introduces conceptual definitions and categories of flexibility, including needed, potential, and feasible flexibility, and explores diverse modeling paradigms ranging from heuristic rules to optimization, data-driven, and physics-based approaches. The paper also discusses recent regulatory frameworks such as the European Flexibility Needs Assessment (FNA) and identifies key criteria for evaluating flexibility requirements across spatial and temporal dimensions. Finally, the report offers a synthesis of emerging practices and highlights the operational, economic, and policy implications of flexibility deployment, supporting informed decision-making in energy system planning and management.

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