Distributed Energy Resource Control and Utility Interconnection Management: Implementation in a Distributed Microgrid

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This article describes the implementation of a brownfield microgrid with the upgrade of existing distributed energy resources (DERs), design of the medium-voltage (MV) interconnection, and implementation of a microgrid control system to meet the U.S. Department of Defense (DOD) needs at Fort Custer, Michigan. Brownfield microgrids involve complexities in design, integration, and commissioning but offer better economic viability due to reduced capital cost upfront. This work tries to identify the challenges associated with brownfield microgrids and provides systematic practical solutions to mitigate them. As part of the upgrades, backup diesel generators were retrofitted to support grid-parallel operation. A battery energy storage system (BESS) was newly installed to manage intermittencies for the existing solar generation and to support the microgrid. The individual DER assets were integrated in a two-level hierarchical microgrid control architecture and controlled in a coordinated manner to achieve seamless islanding and reconnection with the utility grid at the point of common coupling (PCC). The article provides the field data demonstrating the improvement in resiliency through islanded operation as well as maintaining power quality when operating in parallel with the utility. The economic operation of the assets and participation in utility ancillary services were also key goals achieved through the microgrid. This ability allows the military to reduce its total cost of ownership to achieve its mandated energy security needs.