Researchers link minute-by-minute frequency dips to UPS systems — TechCrunch
Researchers at Forschungszentrum Jülich in Germany have found that regular frequency dips in power grids in different countries may be linked to synchronized checks of the charge levels of uninterruptible power supply (UPS) systems and stationary batteries. Such minor deviations were recorded every 60 seconds in Europe, Australia, the United States and Malaysia, TechCrunch reports.
Searching for the source of the fluctuations
A team led by scientist Dirk Witthaut worked to solve the phenomenon after being contacted by Tennet Germany, the country’s largest transmission system operator. Initially, the researchers examined the possibility that hydroelectric power plants were responsible: turbine vibrations can cause resonant oscillations under certain conditions. Modeling showed that resonance with a peak once per minute was possible, but it did not explain why the signal repeated so consistently.
The team installed more than 80 smart power-quality monitoring devices on the Jülich campus. They measured frequency, voltage, current and power every three seconds. At a transformer connected to an energy storage system, the scientists detected minute-by-minute peaks similar to those observed in large power grids.
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Battery synchronization
As the team found, many stationary batteries — from UPS systems in data centers to large grid-scale energy storage systems — check their state of charge every minute. Since such devices are connected to the internet, their timing is almost synchronized. Individually, each check is virtually imperceptible to the grid, but the simultaneous operation of a large number of devices creates a measurable disturbance.
The researchers received additional confirmation from data from Ireland, where data centers accounted for 18% of electricity grid load in 2022. The amplitude of the minute-by-minute frequency drop in Ireland’s grid rose from 3 millihertz in 2016 to 12 millihertz in 2021, while more recently some individual dips exceeded 20 millihertz.
Ireland’s 50 Hz grid is designed for deviations within plus or minus 200 millihertz, although the operator aims to limit them to 100 millihertz. The team recommends that manufacturers of UPS systems and grid batteries add random offsets to the schedule for charge checks. Periodic fluctuations were also detected in some Internet of Things devices, including a smart oven and Raspberry Pi clusters.
