A more than twofold increase of distributed energy resources (DERs) in Greece during the last decade has introduced significant challenges for the system operators (SOs), to ensure the reliability and robustness of the power system. The growing share of renewable energy sources (RES), and thus the variability and unpredictability of new net load patterns increase the complexity of grid management. Flexibility plays a key role in addressing this challenge by enabling the system to adapt demand to power generation. In this context, flexibility markets (FMs) is one mechanism for SOs to effectively leverage DERs to enhance grid efficiency and stability. FMs can adopt a sequential or an integrated market structure to enable access to flexibility for grid services, each presenting distinct SOs’ coordination requirements, and resulting benefits and challenges. Typically, the sequential order of flexibility procurement is structured based on the market and the purpose of the flexibility service. For instance, flexibility is first procured by Distribution System Operators (DSOs) for congestion management, followed by the possibility of offering the remaining flexibility to Transmission System Operators (TSOs) for balancing services. In contrast, an integrated market supports the simultaneous flexibility procurement by the SOs, enabling joint optimization of flexibility services across the grids.

In the OPENTUNITY project, an integrated market is investigated, within the pilot site in the Markopoulo area, SW of Athens. In this setup, HEDNO (DSO) and IPTO (TSO) procure flexibility on NODES platform, with NODES being the Market Operator (MO). Flexibility bids of the SOs are being processed together in one single market, considering grid constraints. However, simultaneous flexibility activation across grid levels requires an iteration of coordinated market interactions, leading to a greater complexity in market design. At the pilot site, flexibility of DERs can be migrated upwards for grid services both in DSO’s and TSO’s network. This creates a unique scenario where the coordinated and simultaneous allocation between the SOs is essential for the optimal transmission and distribution system operation. This approach is enabled to resolve congestion issues for the DSO, while enhancing local ancillary services for the TSO. A novel mechanism, referred to as the Coordinator Role (CR), is introduced to oversee this market activity and facilitate coordination among the SOs to prevent conflicts from the flexibility activation across grid levels. The pilot will examine three CR configurations: assignment to the MO, jointly representation by both SOs, and a hybrid model involving both SOs and the MO. In the first configuration, conflicts are resolved via mediated communication by the MO between the SOs; in the second, the SOs coordinate directly among each other; and in the third, the MO manages low-criticality events, with high-criticality ones escalated to the SOs. The traffic light system is utilized to indicate the criticality of flexibility activation beyond a defined limit. The pilot will evaluate these configurations with respect to resolution efficiency, grid-wide optimality, and communication complexity, aiming to identify a coordination scheme that is unbiased, time-efficient, easy to implement, and beneficial across grid levels.