FERC calls for reliability standards for wind, solar and battery storage systems

Inverters are targeted but grid instability problems require a much broader approach.

Thomas Edison with his first steam-powered generator at the Pearl Street Station power plant in Manhattan, New York, which started generating electricity on September 4, 1882.

When Thomas Edison was tinkering with electricity and the idea of what would become the electricity grid, he focused on direct current. Edison’s first electricity generation station, the Pearl Street Station, in Manhattan, New York, started generating electricity on September 4, 1882, using steam engines powered by coal-fired boilers. The Pearl Street Station served an initial load of 400 lamps at the locations of 82 customers, providing electricity at 110 volts DC.

While Edison preferred direct current, partly because he received earnings from his direct current patents, he ran into competition from George Westinghouse, who had licensed Nicola Tesla’s polyphase AC induction motor patent. Westinghouse won the bid to power the Chicago World’s Fair in 1893, leading to Edison accepting alternating current. Tesla’s experiments had convinced him that electric motors were most efficient at 220 volts AC with the generators running at 3,600 RPM, which is 60 revolutions per minute, or 60 Hertz, or 60 Hz. The American standard became 120-volt alternating current at 60 Hz, although most homes have 240-volt alternating current at the service entrance.

To this day, the critical factor underlying the integrity of electricity grids is maintaining a frequency of 60 Hz. If the frequency of the electricity moves outside the range of plus or minus 0.25 Hz, immediate countermeasures are taken to restore 60 Hz. This can be seen on the ERCOT grid between the hours of 8 PM and 10 PM on a recent evening in October, which shows the immediate countermeasures that were taken to maintain the frequency of the grid between 59.975 and 60.025.

Since all generators were initially large steam engines, turning at 60 rotations per second or 3,600 rotations per minute, slight fluctuations in steam flow or other mechanical problems were minimized by the built-in inertia of mechanical rotation. Inertia refers to the kinetic energy stored in large rotating generators in conventional generators that help stabilize the electrical system.

That changed when wind, solar, and battery storage systems were added to electricity grids. In these asynchronous systems, no mechanical generators are turning at 3,600 RPM. The electrical current they produce is direct current, which must be converted to alternating current by inverters, referred to as inverter-based resources, or IBRs, before the electricity is transferred to power grids. Inverters have had a history of tripping offline randomly, creating havoc on power grids. FERC has been monitoring IBR for the last few years and finally decided to enact regulations.

A critical problem that FERC noted in a recent hearing is that a single IBR can have cascading effects on other IBRs on the grid, as other IBRs shut down as a result:

IBRs that enter momentary cessation may act in aggregate and cause a reduction in power output far in excess of any individual IBR’s impact on the Bulk-Power System. The potential impact of IBRs is not restricted by the size of a single facility or an individual balancing authority area but by the number of IBRs or percent of generation made up by IBRs within a region.

In a final ruling released in October 2023, the FERC says at least 12 significant IBR failures have occurred on US power grids since 2016, which caused an average loss of 1,000 MW each. These problems have become significant enough that the Federal Energy Regulatory Commission, FERC, directed the North American Electric Reliability Corp., NERC, to develop reliability standards for inverter-based generation:

The Federal Energy Regulatory Commission (Commission) is directing the North American Electric Reliability Corporation (NERC), the Commission-certified Electric Reliability Organization, to develop new or modified Reliability Standards that address reliability gaps related to inverter-based resources in the following areas: data sharing, model validation; planning and operational studies; and performance requirements.

The Commission is also directing NERC to submit to the Commission an informational filing within 90 days of the issuance of this final rule that includes a detailed, comprehensive standards development plan providing that all new or modified Reliability Standards necessary to address the inverter-based resource-related reliability gaps identified in this final rule be submitted to the Commission by November 4, 2026.

FERC further specified that:

The Reliability Standards must ensure that registered IBRs will provide frequency and voltage support during frequency and voltage excursions in a manner necessary to contribute toward the overall system needs for essential reliability services.

FERC Commissioner Allison Clements said most IBRs can meet performance requirements with simple software upgrades, while Commissioner James Danly noted that the reliability risks are too significant to wait for new standards:

The reliability risks at issue arise from the rapid, widespread (one might say reckless) addition if IBRs, Danly said, noting the issue has been discussed since 2016 and any new standards won’t take effect until the end of the decade. Up to nearly fourteen years to establish mandatory and enforceable NERC reliability standards to address a known and potentially catastrophic, risk to the reliability of the bulk power system is simply too long a time to wait (emphasis added).

My take: The intermittency of wind and solar has become a significant problem for all US power grids. IBR problems must be dealt with as soon as possible. Still, the grid instability problems created by the intermittency of wind and solar require solutions that go far beyond inverters and the need for software upgrades. The problem with wind and solar is that they are, by their very nature, intermittent, unpredictable, and unreliable.

Rather than only requiring improvements in IBRs, NERC and FERC should take this opportunity to enact rules that address the broader need for wind and solar generators to solve their intermittency problems before their power is injected into power grids. Maintaining the integrity of power grids to prevent problems such as keeping their frequency and stability should be shouldered by the generators, not a problem handed off to grid operators. Grid operators will still have to deal with fluctuations in supply and demand that destabilize the frequency of the grids but should not be saddled with the problems of the intermittency of wind and solar.

How wind and solar generators solve this problem is up to them. They can integrate backup power into their operation, such as battery storage, in an integrated package. This would enable wind and solar to become a dispatchable power source, which would stabilize rather than destabilize grids as is the case now.

Considering the grid instability problems that all US grids have had in recent years, coupled with the fact that wind and solar installations are likely to skyrocket due to the continued federal subsidies provided by the absurdly-named Inflation Reduction Act, FERC and NERC need to solve this problem now.

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