Restoring regularity

Print edition : August 21, 2015

WHEN a rhythm stalls, the effect can be fatal: in a power grid it can mean a blackout and in the human heart even death. A research team, comprising scientists from China, India, Russia, the U.S., the U.K., Macedonia and Germany, has developed a new approach to stabilise rhythm and prevent any irregularity in the periodicity of the oscillations. The issue of power grid stability is what triggered this research.

The alternating current (AC) power transmitted has a certain frequency: in India and Europe it is 50 hertz and in the U.S. it is 60 Hz. This regular behaviour can get disturbed when the power input fluctuates over time. The power from coal-fired plants is nearly steady but input from renewable energy sources such as wind is variable. As more and more renewable energy is being wheeled into power grids, the problem of power grid stress could be more frequent. “If the rhythm gets disturbed, the system cannot continue working properly,” said Jürgen Kurths, of the Potsdam Institute for Climate Impact Research in Germany, head of the research team. The work has been published in the journal Nature Communications. The scientists have demonstrated the workability of the method in experiments using chemical reactions. “We demonstrated that the theory applies to an experiment in which the rhythmicity can be restored in a small network of current generating chemical reactions. These reactions involve an ensemble of complex physical and chemical processes with many variables and uncertainties, so it is really surprising how well the purely mathematically derived approach proves to work here. This indicates a remarkable generality,” said Istvan Kiss of Saint Louis University in the U.S.

The scientists studied the interaction of coupled oscillating systems, like two swings oscillating around a common bar, which are known to mutually suppress their vibrations. Related phenomena are known from neuroscience, chemical reactions, and electronic circuits. But until now, one did not know how to restore the rhythm. “We show that subtly delaying the impulse which goes from one element of the system to another, for instance in a power grid, can efficiently restore the previously disrupted oscillations,” said Wei Zou of Huazhong University of Science and Technology, China, the lead author. “Even a feeble deviation can make a huge difference here. Now we hope it will open a door for future research in the field of complex systems science....” They believe that future research could enable their findings to be applied to other complex networks, including processes within body cells and even the cardiovascular system.