Duke Energy Microgrid Proves Interoperability

OpenFMB has been developed as an open architecture to allow distributed energy resources and existing grid equipment to interact with each other.
Published: Fri 01 Apr 2016

Interoperability is fundamental for utilities to enable technologies from different vendors to plug and play and interact by sharing data on a common network. However, while much talked about, it has taken many years for the concept to really take root among all the players in the sector.

With its smart grid and other clean energy initiatives, Duke Energy has frequently been at the leading edge of developments in the sector. This continues with one of the company’s current initiatives, heading the development and commercialization of the Open Field Message Bus (OpenFMB) as a standards-based reference architecture and framework for allowing distributed intelligent nodes to interact with each other.

“It’s taken several years to get to this point,” Dr. Stuart Laval, who is heading the initiative at Duke, told Engerati in an exclusive interview. “We started with a pilot about 5 years ago with a set of systems that traditionally didn’t play together and it took a couple of years to get to the point where they could share data.”

The ultimate goal is to be able to build out an optimally operating grid with distributed intelligence and resources.

An open architecture

Typical ‘nodes’ in this context include the hardware or software components that interface with grid edge devices such as meters, relays, inverters and reclosers, as well as renewable generation and storage.

Under the OpenFMB, communication between them is via common semantics, such as the IEC’s common information model (CIM) and they federate data locally for control and reporting. Additionally, the OpenFMB supports field-based applications that enable a scalable peer-to-peer publish-subscribe architecture using both centralized and distributed logic for harmonized system and device data.

In this way, the OpenFMB aims to reduce latency and create the distributed intelligence capability to manage local grids in the most efficient way based on the local resources and conditions.

Coalition of the Willing

Based on the experience of the earlier pilot, Duke was encouraged to work more closely with vendor partners to demonstrate the feasibility of sharing data in the field, Laval explains.

To this end, a consortium named the ‘Coalition of the Willing’ was formed, starting out with six out of 60 industry vendors who were approached. Subsequently it has built up to 25 – the maximum number considered manageable – including some of the largest grid vendors, who were willing to put their diverse technologies to the interoperability test.

The test was in a microgrid implementation – dubbed COW-II – which was undertaken at Duke’s Mount Holly microgrid test centre in North Carolina. With a subsequent demonstration at Distributech 2016, the first, demonstration phase of the initiative was effectively concluded.

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Microgrid reference implementation

While OpenFMB is aimed at supporting a variety of business cases, the initial use cases were focused on the operation of a microgrid. These included microgrid optimization, i.e. optimizing the generation and dispatch of energy among the various resources; unscheduled islanding transition, e.g. in the case of a grid outage; and the island-to-grid connected transition in which the microgrid is successfully resynchronized and reconnected back to the main power grid without a black start condition after islanding.

Assets in the microgrid include a 100kW PV solar system with smart inverter capabilities, 250kW battery energy storage system, 10kW PV solar carport with EV charging

capabilities, 500kW automated resistive load-bank, grid equipment, wireless devices, an envision room with appliances and smart breaker monitoring and control capabilities and an operations room with commercial application software to monitor and control the microgrid components.

“When the components were installed we were able to do the integration within a week, compared with months or even years that such a system would typically take,” Laval says, highlighting a key benefit of interoperability.

Microgrid interoperability

He adds that an important finding concerns interoperability itself. “We learned that interoperability is a best practice in terms of leveraging existing standards, technologies and data governance practices. Going through the process, we could demonstrate that every system, hardware, software and telecom, remains ‘best of breed’ and could interact without divulging anything proprietary.”

Among other specific findings to date are the following:

• Distributed activities need to be choreographed, especially with equipment and applications running at the millisecond level. Specifically, due to communications and application latencies, equipment did not initially operate in the proper sequence.

• Time accuracy and synchronization become paramount when running microgrid operations. A major challenge to overcome, particularly involving operations at the millisecond level, was ensuring the key equipment and applications ran off the same timestamps.

• Accuracy of sensing equipment becomes more important at the distribution level with microgrid operations. Phasor measurement units (PMUs) are used to collect granular information not typically available in common distribution grid devices, such as phase-angle and frequency measurements.

Power grid standard

Laval comments that a key goal of the project was for the OpenFMB framework to become a new industry standard, which it successfully accomplished with the recent ratification by the North American Energy Standards Board (NAESB). In addition, the Smart Grid Interoperability Panel (SGIP) has adopted the OpenFMB as part of the EnergyIoT initiative to bring the Internet of Things and advanced interoperability to the power grid.

“But we still have some work to do to make OpenFMB practical,” he says. “We need to enhance some of the underlying features, such as security where cybersecurity can be an evolutionary process, and we will be investigating the financial business model implications when considering distributed intelligence and its benefits of combining  multiple functions that were historically valued separately. We also want extend the reference implementation to a variety of use cases – we selected a microgrid because it’s a complex, highly dynamic system and the extension to less dynamic use cases such as distribution automation, advanced metering or demand response should be a logical progression.”

Finally, OpenFMB is also set to be implemented in other utility and laboratory test beds at for example CPS Energy, Southern California Edison, Detroit Edison, EPRI, NREL and Oak Ridge National Labs, while some of the Coalition members are starting to build technology roadmaps to support the standard.

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