A Coordinated Optimal Operation Method for Distribution Networks and Multiple Microgrids Based on Flexibility Margin Assessment

Under the “dual carbon” goals, the large-scale integration of distributed photovoltaics (DPVs) presents a challenge for the flexibility supply–demand mismatch in distribution systems. To address the issue of accurately matching flexibility supply and demand in the process of DPV consumption, this paper proposes a coordinated optimization method for the distribution network (DN)- multi-microgrid (MMG) system, based on flexibility margin assessment. First, the mechanism of flexibility supply–demand imbalance under high penetration of DPV is analyzed, and a flexibility margin index considering network constraints is developed to quantify the flexibility surplus or deficit at different levels and periods. Next, within the framework of energy interaction between the DN-MMG systems, a centralized collaborative optimization model is established, aiming to enhance global flexibility margins. This model coordinates power exchange between nodes and the inter-temporal dispatch of energy storage, achieving the collaborative utilization of various flexibility resources. Finally, a case study based on a 10 kV distribution system with MMGs in a northern region is presented. The results show that the proposed method can effectively improve the spatiotemporal matching of system flexibility, reduce the risks of solar power curtailment and load shedding, while enhancing the economic performance of the system and the capacity for DPV integration.