The Midwest’s bulk power grid and wholesale market operator, MISO, has unveiled a new plan to improve the reliability of standalone battery energy storage systems.
MISO is proposing a framework that would require developers and asset owners to deploy batteries that incorporate “grid-forming” inverter technology as opposed to “grid-following” controls, which rely on tracking grid voltage set by other resources.
The plan, which MISO said would be “flexible” to incorporate ongoing feedback from stakeholders, includes several functional capability and performance requirements defining voltage source characteristics, as well as required simulation tests to demonstrate grid-forming characteristics and stable control responses. MISO said it is only targeting software enhancements and the plan would not require hardware upgrades.
MISO’s approach to improving battery storage system reliability reflects repeated warnings from the North American grid reliability monitor that inverter-based resources like solar and wind power plants, as well as battery storage systems, are misbehaving as a result of typical grid disturbances.
The North American Electric Reliability Corporation (NERC), which oversees the reliability of the bulk power system, has issued more than a dozen reports in recent years diagnosing the shortfalls of inverter-based resources. Some incidents are what the grid watchdog identifies as “faint signals” of broader implications. Others have teetered on complete grid collapse. The disturbances have not, to this point, caused blackouts on their own. But that’s due to IBRs playing a relatively still-small role in the power system. As renewable energy rapidly displaces fossil-fueled, synchronous sources, those “faint signals” may lead to systemic failures if the industry does not remain vigilant in addressing these underlying reliability risks.
MISO said its proposed requirements “borrow heavily” from NERC guidance and international work, including grid-forming battery storage standards established by Australia’s grid operator.
“Regardless of the precise amount of (grid-forming controls) that could be needed, NERC’s recent whitepaper points out the opportunity to act now, given commercial availability of technology and the potential cost of inaction,” MISO said.
