A Novel Approach for Bump-less Connection of Microgrids with the Grid

Abstract

Rapidly declining prices of solar PV and storage technologies are leading to widespread deployment of distributed energy resources across the grid at an unprecedented and accelerating pace. Extreme weather events, the need for improved reliability, demand charge reduction, improved power quality, energy arbitrage, fuel diversity, greenhouse gases (GHG) reduction, etc. has spurred and renewed interest in microgrids at the customer, community, and utility level. To achieve seamless/bump-less/transient-free transitions between the islanded and grid-connected modes of operation, most commercially available microgrids either operate in or switch into the isochronous control mode to synchronize generation resources and to maintain phase, frequency, and voltage prior to reconnecting the microgrid with the grid. This method of using a centralized microgrid controller and communicating with every DER fails when considering large geographically dispersed microgrids with numerous DERs such as utility-scale microgrids, community microgrids, etc., as centralized control and real-time communication become infeasible. This paper proposes a novel approach using an Island Interconnection Device (IID) for the bump-less connection of multiple islanded microgrids to form a networked microgrid, and reconnect with the grid in a truly decentralized fashion.