With increasing numbers of microgrid developments, networked microgrids present an opportunity to improve distribution feeder resilience and reliability. Networked microgrids are physically interconnected microgrid areas with controller interoperability that enables multi-island synchronization and coordinated power sharing. This project aimed to demonstrate a solution that reduced the time and cost of designing and implementing microgrids in military installations. Electric Power Research Institute, Inc. partnered with a commercial microgrid controls vendor (S&C Electric Company) and Sandia National Laboratories to design and test a networked microgrid controller. Key concepts of Distributed Energy Resources (DER) power sharing, multilayer network redundancy, sequenced outage recovery, coordinated system protection, and cyber-secure communications were demonstrated. The Final Report (will hyperlink) captures the executed test plan, results, and performance analysis of the networked microgrid controls.

The microgrid controller technology developed in this project aimed to implement a generic process for joining and separating individual microgrids into larger grid sections. Variations on this have been demonstrated previously, but these solutions have been customized to the specific equipment and requirements of the installations  In this project, the S&C GridMaster controller design focused on developing a modular solution that can be adapted to any given configuration of microgrids with minimal setup time and configuration efforts. The tested controller hardware solution is capable of managing various DER combinations and communicating between the controllers and reclosers to join and separate microgrid areas.

The networked microgrid controller concept was capable of meeting minimum performance requirements for the operation of joined microgrids. Across all test scenarios, the joined microgrids operated within acceptable frequency and voltage limits, and the island synchronization process did not cause adverse system conditions. The ability to safely black start, synchronize, and operate joined microgrid islands as a feeder-level island was confirmed in both controller-hardware-in-the-loop and power-hardware-in-the-loop test environments. The operational cost savings observed during the grid-connected test scenarios appear to provide a net benefit but can vary based on local electricity tariffs. Key cost drivers include control complexity, potential upgrades to enable remote control and paralleling of legacy DER, and interconnection assessment.

One of the anticipated benefits of joining microgrids was the ability to share DER output to increase high-priority load coverage across the joined areas during island synchronization. The test network and system conditions simulated in this project phase failed to meet the load coverage performance objectives. However, using the data gathered throughout the testing process, the project team identified several design variables that could be adjusted to improve the joined microgrid performance. In addition, the benefits of power sharing control are expected to be more pronounced under system conditions with higher penetrations of photovoltaic  and larger DER-to-load ratios.