Topology-Constrained Flexibility Assessment of Adjustable Resources in the Regional Electricity Spot Market

The transition toward modern power systems with high renewable penetration has significantly increased the demand for system flexibility. However, existing reserve capacity assessment methods often overestimate the actual deliverable flexibility by neglecting network topology constraints. This paper proposes a topology-constrained flexibility assessment framework based on the Regional Security-Constrained Economic Dispatch (R-SCED) model to quantify the true deliverable reserve of adjustable resources in electricity spot markets. Unlike conventional approaches, the proposed framework explicitly captures the spatial distribution of load increments and their interactions with transmission constraints. Through multi-scenario analysis, we reveal a critical “capacity restriction effect”, where network bottlenecks drastically reduce the theoretically available reserve. Case studies on an 88-node multi-area system show that the actual upward flexibility is reduced from a theoretical level of 67,000 MW to a constrained range of 5200–19,000 MW. The results demonstrate that flexibility in modern power systems is fundamentally limited by network topology rather than generation capacity, highlighting the necessity of topology-aware reserve assessment for real-time market operation. This work provides important insights for improving dispatch strategies and enhancing system flexibility under high renewable penetration.