Among the various standards that must be considered in building a microgrid, there are two that pertain to the microgrid as an entity and its relationship to the distribution utility (macrogrid) – one for interconnection with the macrogrid at the “point of common coupling” (PCC); the other, the microgrid controller for management of the microgrid.
Both of these are receiving much attention from the Smart Grid Interoperability Panel (SGIP) in the United States. The SGIP was established as a public-private partnership by the National Institute of Standards and Technology (NIST) to support its coordination of standards development for the smart grid.
On July 10, 2014, the NIST/SGIP Priority Action Plan 24 (PAP-24) was initiated to further standards for microgrids with respect to interconnection, microgrid controllers and information models.
Coordinated and consistent electrical interconnection standards are necessary at the PCC with the distribution grid. These include communication standards and implementation guidelines. Although there are standards that define the basic microgrid connection and disconnection process (IEEE 1547.4), there are no standards that define the grid interactive functions and operations of microgrids with the macrogrid.
PAP-24 will review the standards requirements at the PCC and the current revision of the IEEE 1547 standard series (1547-REV) for the stable and secure electrical interconnection of distributed energy resources to the distribution grid. PAP-24 is focused on the grid facing functionalities and communications for microgrids (e.g. microgrid to/from macrogrid). The PAP will address also consistency and interoperability of the information models and signals used by microgrid controllers.
“Standards are being developed for advanced microgrids that operate interactively with the distribution utility,” explains Jim Reilly of Reilly Associates, who is the technical lead for PAP-24. “An advanced microgrid communicates in real time and has an interactive relationship for two-way power flows and transactions with the distribution utility on a 24/7 basis. Sometimes the microgrid takes power from the macro grid, and sometimes it supplies it – whatever is optimal at a particular point in time. This is the next step in the evolution of the microgrid.”
The key element necessary for this evolution is the microgrid energy management system (MEMS). The MEMS includes the control functions defining the microgrid as a system that can manage itself, operate autonomously or grid connected, and seamlessly connect to and disconnect from the main distribution grid for the exchange of power and the supply of ancillary services.
The reason for establishing a standard for the MEMS is to enable interoperability of the different controllers and components needed for its operation through cohesive and platform-independent interfaces. This approach will allow for flexibility and customization of components and control algorithms to be deployed without sacrificing plug-and-play, or limiting potential functionality. Microgrid components and operational solutions exist in various configurations with different implementations. Regardless of whether equipment and software are commercial or custom, components should be interoperable, with interfaces that comply with functional standards defined by the MEMS.
To this end, IEEE P2030.7, Standard for the Specification of Microgrid Controllers has been formed, the go-ahead having been given by the IEEE SA Board on June 12, 2014. The scope of this standard covers the technical issues and challenges associated with the operation of the energy management system that are common to all microgrids, regardless of topology, configuration or jurisdiction; and to present the control approaches required from the distribution system operator and the microgrid operator. Testing procedures are also addressed.
Implications for microgrids
IEEE 1547-REV and the new IEEE P2030.7 standard are enablers for the acceptance of microgrids by utilities. “Once utilities know that standards are established and approved for controlling microgrid operations, they will be more comfortable integrating them into their systems,” says Reilly.
“Someday utilities will offer microgrids to customers as a service and entrepreneurs will design and build microgrids for customers or groups of customers and operate them cooperatively with utilities. Markets will change to compensate utilities for microgrid resources, both generation and demand response. Microgrids will participate in ancillary services markets.”
These developments, of course, will not take place overnight. But the IEEE SA, as the standards development organization, is “fast-tracking” the process, from the usual four to five years to two to three.
The NIST/SGIP PAP-24 working group is looking forward to the completion of IEEE 1547-REV by December 2017 and anticipates that IEEE P2030.7 will be available even earlier by December 2016.