Quantifying the Flexibility at the TSO-DSO Interface Under Uncertainties

With the increasing penetration of distributed energy resources (DERs) into power systems, overall grid uncertainty and variability have increased significantly. The transmission and distribution networks both find it challenging to maintain grid stability and security. To address these challenges, flexibility within the distribution network can be crucial in supporting various grid or ancillary services, such as frequency control, voltage control, or congestion management. Hence, this paper focuses on developing an algorithm to assess feasible and flexible regions from the distribution network at the interface of Transmission System Operators (TSOs) and Distribution System Operators (DSOs). This work includes multiple case studies demonstrating the effects of different constraints like line flows, voltage limits, ramp rates, and market dispatch points (MDP) on estimated feasible and flexible charts. Additionally, the impact of load uncertainty on feasible regions is investigated using a robust optimization technique. The proposed methodology under different scenarios is validated through simulations on a modified IEEE 33-Bus System.