Microgrids Drive Duke’s Coalition for Grid-Edge Interoperability

For the past few years, giant U.S. utility Duke Energy has been asking grid companies to join its “Coalition of the Willing” -- a select group of grid vendors working on standardizing the way a whole host of grid-edge technologies can integrate with each other in the field.

It’s taken awhile, but it appears that Duke’s pitch to the industry is starting to gain traction. At this week’s DistribuTECH conference in San Diego, the utility will unveil the next phase in its grid interoperability work, a microgrid being built at its Mount Holly, N.C. test lab -- and a list of coalition partners that’s grown from six to 25.

Duke’s expanded list of partners for what it’s now calling its “COW II” project has lost a few of its original participants. That includes Ambient, the original provider of edge communications nodes for the utility, which went bankrupt last year, as well as Echelon, the former Duke smart meter partners that’s since sold off its smart grid business.

But Duke has added plenty of big smart metering and communications partners, including two already working closely with the utility -- Itron and Cisco -- to make up for their absence. It’s also brought on an interesting mix of communications, grid control equipment and power electronics vendors, as well as some international partners, like Japan’s ITOCHU, that are involved in distributed energy networking and control.

Here’s the full list of COW II partners, with the original partners in boldface:

As for what these new partners will be doing together over the coming year -- and how other utilities and vendors can stay abreast of their progress -- Duke will be covering the basics during a Wednesday session at DistribuTECH. It has also published the reference design specification to be used in the project (PDF). But many of the details of the point-to-point system integrations that will unfold at Duke’s test site are still open, Jason Handley, director of operations and projects for Duke’s Emerging Technology Office, said in a Friday interview.

“We aren’t exactly sure what some of the underlying use cases are that would come out of the work,” he said. "We didn’t want to pigeonhole anyone, saying, ‘You do this; you do that.’ Maybe two companies that never thought about working together before now can -- and that solution will be interoperable.”

There are two rules for participating vendors, though. The first is, “whatever you do has to conform to an open, interoperable messaging protocols,” he said. Those include a data model based on the Common Information Model utility standard, implemented into an open field message bus, which refers to the “field bus” that allows distributed devices to connect via the communications nodes that Duke is deploying as part of its smart meter rollouts.

The second rule is, “you have to implement publish-subscribe protocols, like DDS or MQTT,” he said. MQTT stands for Message Queue Telemetry Transport, and is a lightweight machine-to-machine communications protocol for data transfer situations with limited bandwidth. DDS stands for Data Distribution Service, a secured messaging protocol originally developed by the U.S. Navy to connect shipboard IT systems in a real-time, peer-to-peer network, that’s been put to use in microgrid pilot projects involving coalition partners National Instruments and RTI.

Duke’s test site will incorporate a solar- and battery-powered microgrid, capable of islanding from the grid for short periods of time and running on its own power. Unlike almost all the microgrids now running today, Duke’s will have no backup generators or other spinning power resources -- “This is an inverter-only microgrid,” he said.

The test site already has plenty of solar panels, advanced inverters and grid-tied batteries to work with. The utility will be adding new pieces to that puzzle, including a small house where grid-connected water heaters, air conditioners, and other load control devices can be tested, Handley said. “We’re also able to go back up into the grid,” he added. “We’re going to have reclosers, capacitor banks, regulators, line sensors, streetlights, and standard grid hardware, all tied back into the microgrid.”

Duke’s long-range hopes for this grand experiment in multi-vendor interoperability are twofold, he said. “The first goal is to promote interoperability between devices. The second is for Duke to find out if we can potentially offer microgrid services in the future.”

Duke’s Emerging Technology office isn’t commercializing this utility-managed microgrid concept, only seeking to show that it could be technically and economically feasible, he said. “The key is [whether] we can get this many separate vendors to agree to do something in common,” he said.

“We believe through a standardized process, we will be able to implement much faster and at a much lower price,” he said. Just how utilities may play a role in installing, managing or even owning customer-sited energy assets like solar panels, smart inverters or energy storage remains to be seen, of course. But the first step remains to show it can be done.