A long-term congestion management framework through market zone configuration considering collusive bidding in joint spot markets

The zonal market (ZM) adopted in Europe, in contrast to the nodal market (NM), reconciles the inconsistency between physical networks and administrative management. However, the growing integration of renewable energy sources (RESs) has introduced zonal supply-demand imbalances that exacerbate congestion and the need to re-dispatch. Furthermore, different clearing mechanisms between the day-ahead and real-time markets provide further opportunities for collusive bidding, decreasing total social welfare (TSW). Thus, this paper is the first to propose a long-term congestion management (CM) framework through a market zone (MZ) configuration approach with CM assessment considering collusive bidding in the joint spot markets. More specifically, a topology-based location division (TLD) method is proposed to partition optimal MZs, ensuring the minimum number of MZs based on critical branches. Then, a bi-level evolutionary model is developed to analyze the collusive bidding of producers in the day-ahead and ancillary service markets. Finally, the established framework is applied to a 20-bus test and simplified European systems. Our simulation on the 20-bus system shows that compared with the initial ZM and NM, the congestion cost of the optimized ZM decreased by 90% and 33%, respectively, while the TSW increased by around 13% and 1%, respectively.