Like TV pickup, where advert breaks in television cause surges in power demand.
The classic example is everyone making a cup of tea at the same time during the World Cup half time break.
Something as common as predictable as every minute should be simple to model in.
The article says as much:
> The identified synchronization mechanism is not specific to UPSs or battery systems, but reflects a general property of digitally controlled devices operating with external timing signals or periodic software routines