One factor driving the grid of the future is the change in the nation’s electric generator resource mix, such as the retirement of traditional baseload generation and an increasing proportion of variable energy resources, such as wind and solar.  This evolution has raised concern that the capability to provide “primary frequency response,” a critical grid support service, is declining.  FERC, concerned with potential grid reliability problems, issued a Notice of Proposed Rulemaking (NOPR) that would require new generators to have the equipment to provide the service and to provide it when needed. The North American Electric Reliability Corporation, the group responsible for developing and administering reliability standards, said that “[f]requency response is among the essential reliability services critical to the reliability of the bulk power system.  The NOPR recognizes the importance of frequency response as the generation resource mix undergoes rapid change.” Background The reliable operation of the alternating current (AC) North American electric grid  depends on maintaining a frequency near 60 Hertz (Hz).  Changes in frequency are caused by changes in the balance between load and generation, such as the sudden loss of a large generator or a large amount of load.  If frequency deviates too far above or below 60 Hz, the result could be load shedding, generation tripping, or cascading outages. Frequency response is a measure of the grid’s ability to arrest and stabilize frequency deviations.  Primary frequency response actions begin within seconds after system frequency changes and are mostly provided by the automatic and autonomous actions (i.e., not directed by the system operator) of generator turbine-governors.  Some response is provided by frequency responsive loads. Synchronous generating facilities with standard governor controls have been the predominant sources of electricity generation.  However, those synchronous generating facilities are being replaced, in part, with non-synchronous variable energy resources such as wind and solar.  FERC observes that variable energy resources have not typically contributed to system inertia or had primary frequency response capabilities.  Importantly, however, FERC notes that the technology now exists for new non-synchronous generating facilities to install primary frequency response capability. The proposed rule FERC proposes to require new generators to have frequency response capability.  It implements this requirement by proposing new provisions in the standard interconnection agreements by which public utility transmission providers provide interconnection service to the grid.  Existing standard interconnection agreements are largely silent on any requirements regarding primary frequency response because they were developed when traditional synchronous generating facilities were predominant. The NOPR would revise the standard interconnection agreements in the following ways:

  • Require new generating facilities to install and operate equipment that provides frequency responsive real power control with the ability to sense changes in system frequency and autonomously adjust the generating facility’s real power output.
  • Prohibit all new generating facilities from taking any action that would inhibit the provision of primary frequency response, except under certain specified conditions.
  • Require new generating facilities to respond to frequency deviations and sustain the response until at least system frequency returns to a stable value.

FERC does not propose that a generator receive any compensation for these proposed requirements.  However, the NOPR clarifies that a public utility may file a proposal for primary frequency response compensation. The proposed revisions would apply to:

  • New generating facilities that execute interconnection agreements on or after the effective date of a Final Rule; and
  • Any generating facility that has an executed or filed interconnection agreement as of the effective date of a Final Rule, but takes any action requiring a new interconnection request that results in an interconnection agreement filed on or after the effective date of a Final Rule.

FERC proposes to exempt nuclear generating facilities from the proposed reforms due to their unique operating characteristics and the regulatory requirements of  the Nuclear Regulatory Commission. Comments on the proposed rule are due on January 24, 2017.