The paper addresses market-based congestion management (MBCM) in electric power systems utilizing aggregators of dispersed small-scale (residential, commercial and small industrial) electricity consumers, producers and prosumers at the distribution network. The proposed method is based on the market principle, where the system operator performs minimum-cost redispatching of generators, loads and aggregators as to relive congested lines. The power system is linearized and presented by the direct current (DC) model for power flow calculation. In this way, Power Transfer Distribution Factors (PTDFs) and Topological Generation and Load Distribution Factors (TGDFs and TLDFs) which describe the relation between generators/loads/aggregators and line-power flows are applied. The proposed solution applies two decoupled optimizations. The upper-level optimization includes bid-based redispatching for congestion relief, while low-level optimization provides the optimal bid of an aggregator for the MBCM procedure, where block offers are introduced for aggregators that have multiple connection points (MCPs) to the transmission network and inject power synchronously at different locations. Both optimization problems are solved by linear programming. Case studies show the applicability of the proposed congestion management method on a simple test model of a power system.
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