Coordinated disturbances haunt grids worldwide. Here’s how researchers solved the mystery.

Stationary batteries, including data center UPS, may soon start randomizing their charge-check intervals to prevent grid disturbances.

Researchers have identified the cause of mysterious, minute-long frequency sags plaguing power grids worldwide: the synchronized state-of-charge checks performed by battery energy storage systems, particularly Uninterruptible Power Supplies (UPS) in data centers. This anomaly, occurring every 60 seconds, was observed across continents, baffling grid operators. Initially suspected to be related to hydropower turbines and ultra-low frequency oscillations (UFLOs), the consistent, clockwork timing of the sags led Dirk Witthaut at Forschungszentrum Jülich to investigate devices with internal clocks. By deploying power quality meters and analyzing grid data, particularly from Ireland where data centers represent a significant electrical load, the team confirmed that the collective digital checks of battery charge levels create a detectable, albeit small, disturbance. While current grid infrastructure can generally accommodate these sags, their aggregation with other grid disturbances could pose a risk of blackouts.

The discovery that synchronized UPS checks are causing grid frequency sags has significant implications for the stability of electricity networks, especially as data center power consumption continues to rise globally. This phenomenon highlights a previously unrecognized systemic risk arising from the interconnectedness of digital infrastructure with physical grid operations. The solution, a simple software patch to introduce randomization in checking schedules, is straightforward but requires manufacturers and operators to implement it, potentially necessitating regulatory intervention.

This breakthrough is particularly relevant as the world relies more heavily on digital services, underscoring the need for a holistic approach to grid management that accounts for the impact of emerging technologies like large-scale battery storage and IoT devices. While the immediate threat may be manageable, the potential for similar, unaddressed synchronization issues to emerge with other interconnected digital systems warrants proactive research and standardization efforts to ensure future grid resilience.