Resource-adequacy and reliability issues could be partially alleviated through increased interconnection of distributed energy resources, but such integration must be handled carefully to avoid complications that could lead to unintended consequences, utility representatives and experts said during a Feb. 18 workshop held by the New Mexico Public Regulation Commission.
Arthur O'Donnell, a U.S. Department of Energy fellow, is assisting the NMPRC with issues related to grid modernization, vehicle electrification and renewables integration. "A first effort is to update the state's distribution Interconnection Rules and Manual and adopt [Institute of Electrical and Electronics Engineers] 1547-2018 standards for advanced inverter functionalities and other DER devices," O'Donnell said in an email to California Energy Markets.
NMPRC member Cynthia Hall facilitated the remote workshop, intended to inform a decision on whether to conduct a formal rulemaking. Interconnection of distributed energy resources is also an important component of the state's strategy to achieve emissions-free power generation by 2045, Hall said at the workshop.
The vast majority of distributed resources in New Mexico are residential and small commercial solar photovoltaic, but Public Service Company of New Mexico, the state's largest utility, said it has begun receiving applications to interconnect microgrids and batteries and anticipates applications for community solar interconnection.
Andrea Contreras, manager of customer interconnection for PNM, said the utility had nearly 24,000 DER interconnections on its system at the end of 2020, with 6,598 interconnection applications having come in during that year. The phasedown of federal tax credits from 26 percent in 2020 to 22 percent in 2021 helped drive applications, Contreras said. Solar contractors were also able to take advantage of more customers being home as a result of the COVID-19 pandemic to install PV systems in 2020, she added.
PNM also makes available a feeder capacity map that shows contractors and distributed generation customers the potential for interconnection in a given area.
Utility representatives agreed that New Mexico's interconnection rules should reflect the current IEEE 1547-2018 standards for interconnection and interoperability of distributed energy resources and electric power systems, which will necessitate updating the state's interconnection manual to reflect conformance and testing procedures for interconnecting resources as specified in IEEE 1547.1-2020.
"I think that if we have a joint effort between PNM and [other] investor-owned utilities . . . we could really have a quality product," Roberto Favela of El Paso Electric said during his presentation.
Others at the meeting stressed the value of collaboration and forming working groups to create effective rules for interconnection. Ken Wilson, an electrical engineer with Western Resource Advocates, said his organization has assisted several states in updating interconnection rules to comply with current standards. The process gives stakeholders an opportunity to customize rules so that they reflect the particularities of each state. California's interconnection manual is about 100 pages, Wilson said, while Arizona's, with fewer interconnections and less complexity, is about half the size.
Sky Stanfield, an attorney representing the Interstate Renewable Energy Council, said upgrades should be seen as an inevitable part of the interconnection process and that good policy would plan for and enable them. Technology development is moving faster, and states are getting serious about interconnection to meet their renewables portfolio standards, she said.
It is very easy for states to fall behind on standards as technology advances, Michelle Rosier, distributed energy resource specialist at the Minnesota Public Regulation Commission, added. Minnesota has addressed this with a standing DER interconnection working group that meets at least annually. Statewide standards must meet the needs of diverse utilities, she said, adding that facilitation and compromise within the working group is key to establishing effective rules for a broad array of utilities and DER customers.
Kyle Reddell of Southwestern Public Service, which serves utility customers in southeastern New Mexico and western Texas, explained during his presentation that the minimum daytime loading of substations generally limits solar system interconnections to less than 5 MW to prevent flowback onto the transmission system. Larger systems are studied by the Southwest Power Pool, of which SPS is a member, for their impact on the transmission system, Reddell said.
Michael Ropp of Sandia National Laboratories in Albuquerque focused on technical issues surrounding interconnection. These can include a lack of dispatchability and interoperability, problems with voltage regulation, the need to prevent DERs from impeding utility functions, unintentional islanding, and the impact of large DER fleets on bulk-system dynamics.
The new IEEE standards, issued in 2018 after a 15-year gap, are designed to keep voltages within tolerance and to keep DERs on line to supplement resource adequacy, Ropp said. Previous standards encouraged the withdrawal of DERs from the grid at any indication of potential problems. "Now we've got enough DERs out there that we don't really want them to do that because it causes another problem if they do," he said. They are now required to stay on line much longer through larger deviations in voltage and frequency, "so that we don't get these big drops in resources just when we need it the most."
The Electric Reliability Council of Texas saw its lowest system frequency ever during the storms this week, Ropp said. "In a case like that, you need your DERs to be able to take certain actions to help you out. So some of those capabilities are also in the new standard." He noted that the term "interoperability" is in the new standard's title to help establish protocols to ensure devices can communicate with each other.