| Summary: | More and more distributed energy resources (DERs) are being integrated into the distribution networks raising the new concerns of secure and economic operations. Some traditional distribution networks are upgraded to active distribution networks (ADNs) which can communicate with and control the DERs. A microgrid connected to an ADN can be coordinated with the ADN. In this paper, a two-stage hierarchical congestion management mechanism is proposed for an ADN connected with multi-type DERs and microgrids. At the first stage, a hierarchical optimization model is built considering the dispatch of direct control resources (DCRs) and microgrids. An analytical target cascading (ATC) method is employed to optimize the microgrid autonomy model and the ADN optimization model simultaneously. A second stage optimization is designed to deal with the case when the control of DCRs and microgrids is not enough to completely eliminate the congestion. A congestion management model calling for the ancillary services provided by DERs is established, with an objective of minimizing the operational cost of distribution system operator (DSO). Case studies are carried out on modified IEEE 33 and PG&E 69 bus systems. The simulation results show that the proposed method can balance the interests of different stakeholders and eliminate the network congestion efficiently.
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