November 12, 2025
Grid-forming (GFM) resources are poised to play a key role in maintaining the reliability and stability of modern power systems with high levels of inverter-based resources (IBRs) and large electronic loads (LELs). Proactive deployment of GFM technologies can help mitigate reliability challenges that would otherwise require extensive transmission investments. To support their adoption, well-defined test methods and performance metrics are needed to evaluate and specify GFM behavior.
This webinar presents the findings from the newly released ESIG report, “Testing the Voltage Source Behavior of Grid-Forming Resources,” which provides comprehensive guidance for assessing the voltage source behavior of both inverter-based and rotating machine–based resources.
The report introduces a structured suite of time-domain and frequency-domain tests that quantify how closely a resource behaves as an ideal voltage source with an impedance—a critical factor in enhancing grid strength and supporting bulk power system stability. The report further defines performance metrics for each test and offers example specifications that demonstrate how voltage source behavior requirements can be applied in procurement while maintaining flexibility across GFM technologies. Finally, it links the quantified voltage source behavior of GFM resources to grid strength improvement and IBR stability margins, enabling their use in sizing GFM capacity for targeted system strength enhancement.