3.7 Interoperability, DER Interconnection, and Communication Standards and Technologies

3.7.2 IEEE 1547 Status

The interconnection requirements of most jurisdictions are based on the Institute of Electrical and Electronics Engineers (IEEE) 1547 DER interconnection standard.  The interconnection requirements of most jurisdictions are based on the Institute of Electrical and Electronics Engineers (IEEE) 1547 DER interconnection standard.  Section 1254 of the Energy Act of 2005 requires IEEE 1547 unless other requirements are developed by local PUCs:

SEC. 1254. INTERCONNECTION.(a) ADOPTION OFSTANDARDS.—Section 111(d) of the PublicUtility Regulatory Policies Act of 1978 (16 U.S.C. 2621(d)) isamended by adding at the end the following:(15) INTERCONNECTION.—Each electric utility shall makeavailable, upon request, interconnection service to any electricconsumer that the electric utility serves. For purposes of thisparagraph, the term “interconnection service” means serviceto an electric consumer under which an on-site generatingfacility on the consumer’s premises shall be connected to thelocal distribution facilities. Interconnection services shall beoffered based upon the standards developed by the Instituteof Electrical and Electronics Engineers: IEEE Standard 1547for Interconnecting Distributed Resources with Electric PowerSystems, as they may be amended from time to time.In addition,agreements and procedures shall be established wherebythe services are offered shall promote current best practicesof interconnection for distributed generation, including but notlimited to practices stipulated in model codes adopted byassociations of state regulatory agencies. All such agreementsand procedures shall be just and reasonable, and not undulydiscriminatory or preferential.

At the time it was first developed, high penetrations of DER systems were not yet foreseen as a major issue, so the current version of IEEE 1547(2003) requires that systems interconnected to the distribution grid automatically shut-off in the event of even a brief power system anomaly. Therefore that version of the IEEE 1547 standard prevents DER systems from providing any type of grid support or from “riding-through” short-lived anomalous conditions, and thus prohibits DER systems from actively participating in distribution system operations.

As higher penetrations of DER systems started to have undesirable impacts on the grid and as the potential benefits of emerging DER capabilities became better understood, for instance, during California’s Smart Inverter Working Group (SIWG) effort, the IEEE recognized that an update to the 1547 interconnection standards was required.  In mid-2013 the IEEE members of the 1547 standards community initiated a “fast-track” amendment to IEEE 1547, labeled IEEE 1547a.

Balloted and approved by IEEE in September 2013, IEEE 1547a is a “permissive” update to the existing IEEE 1547: its main purpose is to permit some DER actions that are not currently allowed in the IEEE 1547 standard. For example, IEEE 1547a permits the DER system to actively regulate voltage at the point of common coupling under certain conditions. IEEE 1547a also permits the high and low limits of voltage and frequency to be extended for specific time periods so that voltage and frequency ride-through by DER systems can occur.

Additional related efforts include the development of IEEE 1547.1a and IEEE 1547.8. IEEE 1547.1a will provide the testing requirements for IEEE 1547a, and therefore will serve as an addendum to the original IEEE 1547.1 testing requirements. Coordination between the UL 1741 testing and certification requirements and these IEEE testing requirements are taking place.

Additional IEEE 1547 series standards have also been developed over the last few years to address specific types of issues, ranging from islanded grids, to communications, to the types of studies needed to ensure safe interconnections, and to high penetrations of DER (see Figure 16). IEEE 1547.8 provides recommended practices for high penetrations of DER and is still in progress, but is expected to extend the permissive capabilities in IEEE 1547a with specific recommendations for DER functions and settings in high-penetration scenarios. In addition, the base IEEE 1547 standard is being updated to reflect the new DER requirements, with expectations of rapid progress given both California’s and Hawaii’s experiences.

Figure 16 : IEEE 1547 series of DER Interconnection Standards

The IEEE standardization process necessarily takes a long time to ensure the recommendations are both appropriately constrained and yet flexible enough for utilities operating under a wide range of grid conditions, from the Hawaiian Islands to the congested East Coast. However, California’s expectations for distributed generation and the observed impact of higher penetration levels in other countries led the CPUC and the CEC to establish the SIWG and pursue development of the technical steps needed to optimize the role of distributed generation in supporting distribution system operations. 

One of the areas of discussion in the updating of IEEE 1547 is exactly where the focus should be: the PCC (as in the IEEE 1547:2003) or the ECP (where testing of DER systems must be done) or some combination. Some inverter-based DER systems may be directly connected to the utility grid, while others may be “behind the meter” in a commercial or industrial facility or as part of a microgrid:

• Point of Common Coupling (PCC): For those ECPs that demarcate the point between a utility EPS and a plant or site EPS, this point is identical to the point of common coupling (PCC) defined as “the point where a Local EPS is connected to an Area EPS” in the IEEE 1547 “Standard for Interconnecting Distributed Resources with Electric Power Systems”.
• Electrical Coupling Point (ECP): In either case, the inverter-based DER systems will have a point of electrical connection, which is defined as: “The electrical coupling point (ECP) is the point of electrical connection between the DER source of energy (generation or storage) and any electric power system (EPS). Each DER (generation or storage) unit has an ECP connecting it to its local power system; groups of DER units have an ECP where they interconnect to the power system at a specific site or plant; a group of DER units plus local loads have an ECP where they are interconnected to the utility power system.

Many functions reflect conditions at the DER’s ECP. For instance, the measured voltage levels used for volt-var management are those at the DER’s ECP. Other functions would need to reflect the PCC, such as limiting output at the PCC.

ECPs are also hierarchical, such as in a university campus environment where the PCC is between the campus and the utility, but where multiple ECPs exist for the different DER systems located in different university buildings. Requests for DER actions can be made at the highest level, say for volt-var settings at the PCC. The university DER energy management system would then allocate different volt-var settings for each of the DER ECPs to reflect their DER capabilities, the needs/desires of the university buildings (people), and the overall campus reliability and efficiency requirements.

This hierarchical concept is illustrated in Figure 17.

Figure 17 – Electrical Connection Points (ECP) and Point of Common Coupling (PCC)