A Distributed Dual-Optimization Framework for Ancillary-Service Coordination Between MV Microgrids and LV Distribution Networks

This article aims to develop an efficient distributed real-time strategy for internal device scheduling and ancillary service coordination in the interconnected system of a medium voltage microgrid and a low voltage distribution network (LVDN). A distributed agent-based dual engine is proposed for coordinated ancillary service optimization, thereby reducing communication and computational burden. The strategy enables the microgrid operator and the LVDN aggregator, which are selfish entities, to perform ancillary service power exchanges by coordinating for both the active/reactive power as well as the compensation rates. The proposed strategy is numerically validated on a 30-node microgrid-LVDN test system consisting of solar PVs, conventional and renewable distributed generators, loads, community battery, and electric vehicles (EVs). This is shown to be beneficial than simply tracking a power profile by the LVDN or considering fixed compensation rates. Microgrid reduces its total operating cost significantly by approximately 31.78%, while maintaining the voltage and state of charges of EVs and community battery within the operation limit. Further, ancillary service coordination for residential and commercial LVDNs with a car park is analyzed, and the study is extended to consider fast charging of EVs with other related constraints.