Interconnection, interoperability for integration in the Smart Grid
The relationship between interconnection and interoperability is often a source of confusion for engineers. During the development of the IEEE 2030-2011 Smart Grid standard, it was a personal struggle for me to “get” the concept of interoperability and how it related to power systems interconnection. Once I understood the perspectives of Information Technology (IT) and Communication Technology (CT), I realized that the systems-of-systems view employed and recommended in the IEEE 2030-2011 Smart Grid guide standard was extremely powerful.
Interconnection is a widely known concept and the fundamental area covered by the IEEE 1547 series of standards. Generally it deals with all equipment and functions used to interconnect a distributed energy resource unit with an area electric power system (distribution system). Interconnection to the distribution system has been well documented and discussed in the IEEE 1547 series of standards.
Interoperability is the capability of multiple networks, systems, devices, applications, or components to exchange and use information securely and effectively. It is helpful to define the key terms describing the different perspective: IT classifies the types and methods of information exchanged between entities that interact with the Energy Storage System. This includes a fundamental classification as Command and Control (intermittent and/or periodic), Monitor Data (periodic), or Alerts & Alarms (intermittent). Additionally the purpose of the information exchanged could be: Operational/Functional, Management of Assets and Infrastructure, Regulatory, Pricing and Markets, or Security.
CT deals with the network paths available to transport that information. These parameters can include: protocols (IEEE 802), connection medium (wired, wireless), latency (milliseconds), and many others
Interoperability is used in many other standards. It is helpful to see how pervasive it is. The table below lists the definition of interoperability used in some other standards.
|IEEE Std 1232-Standard for Artificial Intelligence and Expert System Tie to Automatic Test Equipment||The ability of two or more systems or elements to exchange information and to use the information that has been exchanged|
|ISO/IEC 14536 : 1995 [ANSI/IEEE Std 896.5, 1995 Edition] Information technology Microprocessor systems||The capability for units of equipment to work together to do useful functions.|
|IEEE Std 1003.23-1998 IEEE Guide for Developing User Organization Open System Environment (OSE)||The ability of two or more systems to exchange information and use the information that has been exchanged mutually|
|IEEE Std 610.12-1990 IEEE Standard Glossary of Software Engineering Terminology||The ability of two or more systems or components to exchange information and to use the information that has been exchanged|
Although some of them are no longer in use, you can see the pattern…
In Distributed Energy Resources systems, specifications commonly leave out specific requirements for CT and IT, deferring this to the utility.
The benefit of common nomenclature and recommendations for applications is that, over time, communication requirements will be specified using the same terms in the same order repeatedly, eventually leading to modular solutions. This will drive lead times and reduce cost. This is happening as the standards development community takes a deep dive into specific applications and defines these requirements, so they can be applied repeatedly. For example, the IEEE P2030.2 is developing a guide for applying these concepts to energy storage systems connected to the electric power system.
The most recent developments that lay a path to improving interoperability are included in the IEEE 2030 series of standards, with IEEE 2030-2011 being the cornerstone. This guide standard introduces the Smart Grid Interoperability Reference Model (SGIRM) that organizes all the functions and interconnections of a Smart Grid in terms of three separate perspectives that together comprise the Smart Grid:
- The Power Systems (PS-IAP) Perspective defines the Smart Grid in terms of power entities and their interoperability.
- The Communications Technology (CT-IAP) Perspective defines the Smart Grid in terms of communications paths.
- The Information Technology (IT-IAP) perspective describes the Smart Grid in terms of information flows, entities, and protocols used to exchange that information.
In this Standard Guide IEEE 2030.2, we apply the SGIRM to electrical energy storage systems by defining the PS-IAP, CT-IAP and IT-IAP for specific applications and use cases of electrical storage systems.This is an important topic in that we will gradually see the CT and IT requirements communicated along with power systems requirements in specifications for projects and products. As the method and nomenclature become more familiar to consulting and specifying engineers, the entire system specification can become more modular. Modularity leads to subsystem optimization and may lead to lower total system costs. I suspect we may first see this in the modularity of SCADA, facility communication systems, and security systems.The electric power infrastructure is transforming from a system of power interconnections to a very complex diverse, interconnected, interdependent, and adaptive system. Work needs to continue to adapt interconnection standards to current needs. These efforts will lead to a better comprehension of interoperability requirements and the best approaches to interoperability.
Mark Siira, ComRent International, is chair of IEEE P2030.2 Guide for Interoperability of Energy Storage Systems to the EPS.