If the SST is the heart of FREEDM, then DGI is the brain. DGI utilizes an energy management system based on fog computing — an architecture that distributes resources and services between the cloud and internet-enabled devices — to manage the cooperation of power electronics on the grid through localized intelligence. Consensus-based algorithms handle energy management, provide Volt/VAR support and fault detection, and manage the configuration when new sources join the system. Bringing computation and communication closer to the distribution system resolves issues with latency, network bandwidth and geographic focus.
The FREEDM concept of cyber-physical security is an inherent part of DGI’s algorithms. As a fog, DGI supports multiple interacting security domains secured by common data and physical information flows. Static and dynamic invariants are evaluated among components to create this trusted system.
DGI’s common code has been installed on the Green Energy Hub testbed and Hardware-in-the-Loop testbeds at most FREEDM partner universities. DGI integrates with Open DSS, RTDS and PSCAD.
In year 10, researchers migrated Volt/VAR control algorithms to the Green Energy Hub testbed. The scheme was extended to include traditional devices such as voltage regulators and new devices like the SST. Decomposing the problem into a slow voltage-control loop and a fast reactive power-control loop increased computational efficiency. Fundamental work on system stability using Lyapunov level sets is ongoing. DGI’s broader impacts have expanded significantly into securing other electric power and municipal water infrastructures.
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