Frequency Response Initiative Report: The Reliability Role of Frequency Response

System planning and operations experts are anticipating significantly higher penetrations of renewable energy resources, most of which are electronically coupled to the grid. This presents some new and different technical challenges, particularly in the reduction of system inertia through the displacement of conventional generation resources during light load periods. Load management and other demand-side initiatives also continue to grow. Most importantly, a continued downward trend for frequency response over a number of years has raised concern that credible contingencies may result in frequency excursions that encroach on the first step of under-frequency load shedding (UFLS). Such large frequency excursions could also trigger undesirable reactions from frequency-sensitive smart grid loads and electronically coupled renewable resources. Taken together, it is clear that maintaining adequate frequency response for bulk power system reliability is becoming more important and complex. While the decline in frequency response has lessened in the last couple of years, it is important that the industry understands the growing complexities of frequency control and is ready with comprehensive strategies to stay ahead of any potential problems.

NERC has undertaken various activities over the past few years in an effort to understand the steady decline in frequency response, particularly in the Eastern Interconnection. While some significant insight has been gained and system-wide and technical improvements have been achieved in the Western Interconnection and ERCOT, a deeper and more dedicated effort is needed.

To comprehensively address the issues related to frequency response, NERC launched the Frequency Response Initiative in 2010. In addition to coordinating the myriad of efforts underway in standards development and performance analysis, the initiative includes performing in-depth analysis of interconnection-wide frequency response to achieve a better understanding of the factors influencing frequency performance across North America.