Flexibility evaluation framework integrating supply and demand for high renewable share power systems

Flexible resources (FRs) in power systems serve as a critical enabler for integration of high share renewable energy. Conventional planning practices mainly focus on supply-side FRs while neglecting demand-side flexibility potential, challenging coordination of multi-source flexibility contributions. This paper presents a comprehensive flexibility evaluation framework integrating both supply- and demand-side resources. First, operational models characterize supply-side FRs (thermal, hydro and pumped storage) and demand-side FRs — including centralized air-conditioning systems with cold storage (CAC-CS), plug-in electric vehicles (PEVs), distributed battery storage (DBS), and time-shiftable appliances (TSA)—with parameters extracted from multi-source datasets. Second, a tri-dimensional flexibility metric system encompassing energy shifting, power balancing, and ramp rate is proposed, anchored by baseline net load. Third, a case study of a provincial power system reveals three key trends as the renewable penetration ratio (REPR) rises to 50%: 1) increasing system flexibility requirements dominated by power surplus and upward net load ramping, 2) shifting roles of coal plants toward deficit injection (surplus metrics dropping by >80%) and enhanced pumped storage utilization (4–10 times rise in surplus and ramping metrics), 3) PEV and CAC-CS account for approximately 50% energy shifting flexibility in each season and show similar variation trends in metrics to pumped storage. The framework enables coordinated source-load flexibility planning, demonstrating demand-side FRs' capacity to offset conventional flexibility limitations and support renewable integration targets.