Many of today’s power systems rely on inertia, or the natural tendency of generators synchronized to the system frequency to stay in motion, to correct frequency deviation during power system imbalance events. As grid systems evolve, their increasing levels of inverter-based resources, such as wind, solar photovoltaics, and battery storage, do not inherently provide inertia, but can provide different (sometimes faster or better) kinds of frequency responses. For this reason, system operators transitioning their power systems to renewable energy generation sources are exploring solutions to the reduction of generation synchronized to grid frequency, or the reduction of inertia, so their system can remain stable in the first seconds after an imbalance event.
G-PST hosted a virtual summit in March 2024 focused on addressing inertia’s role in maintaining power system frequency. Over 80 attendees including representatives from 10 power system operators joined the two-day event to share cutting-edge practices and research and offer insight into what research and analysis questions should be prioritized to better understand the opportunities and challenges presented by inertia’s evolving role in managing system stability. The summit served as a forum to share experiences, ask questions, and explore how G-PST can best support system operators as they navigate this evolution and consider what frequency metrics may exist beyond inertia.
Explore presentations from the summit:
Inertia Management on the Power Systems of Ireland and Northern Ireland
Simon Tweed, Eirgrid
ERCOT Control Room Situational Awareness Tools
Luis Hinojosa, Electric Reliability Council of Texas
Operational and Planning Frequency Analysis During the Arrest Period
Lina Ramirez, National Renewable Energy Laboratory
Low Inertia System Operation
Dr. Xiaoyao Zhou, National Grid ESO
Initial outcomes from the summit include:
- Inertia isn’t a hypothetical issue. Systems are already starting to run up against inertia constraints, and new ways of thinking about frequency stability will support accelerated integration of renewables.
- While needs will vary with system contexts, high-IBR systems will likely need to procure frequency support from a diverse portfolio of technologies including IBRs themselves.
- Both RoCoF and nadir matter. RoCoF is critical for avoiding tripping protection schemes, and nadir for more general frequency control.
- IBR-dominant systems may benefit from new metrics and terms, for example, the concept of an “energy buffer”, of which synchronous mass / mechanical energy is just one possible source. These would come with their own challenges for defining system needs, a useful concept may be a generic “stability margin” as things become more non-linear and less mechanical.
- While inertia has traditionally been viewed as a single, system-wide quantity, there is growing acknowledgement of the importance of both procuring services and monitoring performance with higher spatial granularity.
- Similarly, the concept of inertia is oversimplified; there is value in establishing more clarity and consistency on what we mean when we say “inertia” (as opposed to the concepts of frequency droop, damping, very fast frequency response, etc.).
- Understanding the frequency stability margin after the largest contingency is key in planning and operations; we need to include it in all horizons to have the resources needed in the future and monitor it online to manage stability in real time.
Progress toward solutions for inertia management is already underway through G-PST’s Pillar 2 and Pillar 5 activities. Together with Eskom in South Africa, G-PST is developing an inertia estimation tool for rapidly assessing and managing system stability. Documentation detailing how to integrate the tool into a control center, based on the experience of Eskom’s National Control Center, is under development. G-PST is working with system operator partners to build out a suite of inertia monitoring tools using different approaches, and developing a foundational framework for these tools that will support the development of other kinds of power system operational tools to rapidly make use of the same data.
Explore G-PST’s other resources related to inertia and frequency control.