Early, proactive deployment of grid-forming resources can mitigate reliability challenges that could otherwise require significant transmission infrastructure investment to solve.
The Energy Systems Integration Group (ESIG) has released a new report, Testing the Performance of Grid-Forming Resources: Test Methods and Performance Metrics for Evaluating the Voltage Source Behavior of Grid-Forming Resources, which presents test methods and performance metrics to rigorously quantify the system-strength benefits of grid-forming (GFM) resources.
As power system operators around the world integrate steadily higher levels of wind, solar, and batteries, GFM technology is recognized as a key enabler of reliable high-renewable grids. A number of systems have integrated several GFM battery energy storage systems to ensure stable operation of their grids, and they are the front runners in developing preliminary specifications for GFM resources. Other large power systems have moderate but growing levels of renewables and battery storage, and while they are not yet encountering the need for GFM resources, early deployment of these resources is very valuable. Proactive deployment of GFM resources can mitigate reliability challenges that could otherwise require significant transmission infrastructure investment to solve.
“Grid stability is a major challenge in operating power systems with high levels of inverter-based generation and large electronic loads,” said Shahil Shah, a principal engineer at the National Renewable Energy Laboratory. “Grid-forming resources—such as batteries with grid-forming controls and synchronous condensers—can increase system strength and help mitigate stability concerns. However, the industry still lacks standardized, universally accepted test methods and performance metrics to rigorously quantify the system-strength benefits of grid-forming resources.”
The value of proactive deployment of GFM resources is especially true for the hundreds of gigawatts of battery storage capacity in interconnection queues, because the GFM capability can be enabled relatively easily and inexpensively through software changes. A common refrain from large power system operators is, what is GFM control and how can we specify its requirements? This report is an effort to answer that question.
The report’s main objective is to provide clarity to the industry on evaluating the core voltage source behavior of GFM resources, which is important for improving grid strength and supporting the stability of bulk power systems. These tests help to quantify the qualitative functional requirements that are defined in various guidelines and standards on GFM resources’ performance.
“The core performance requirement of a grid-forming resource is its ability to behave as an ideal voltage source behind a reactor, which enables it to contribute directly to system strength and stability,” said Julia Matevosyan, associate director of ESIG. “It is essential to establish standardized, transparent test methods to evaluate this voltage source behavior to optimize the sizing and placement of grid-forming resources, ensuring reliable integration of inverter-based resources and minimizing costly disruptions or system upgrades.”
Specifically, this report provides guidance for evaluating the extent of voltage source–like behavior exhibited by these resources during a short time frame, as the voltage source behavior forms one of the core performance metrics for GFM resources. The report includes test methods that are well accepted by industry as well as new methods that are still evolving and not yet widely used. And it provides example specifications and performance metrics for test methods that can be tailored to the characteristics of the system where a GFM resource is going to be installed.