Researchers from Case Western Reserve University in Cleveland, Ohio, concerned that the software underlying the safe operation of an upgraded grid isn’t keeping up with the technological advances in the physical components of those grids, are proposing a method to correct lagging software in large-scale distribution systems.

"We need new methods for calculations of emerging distribution systems to properly model and calculate these systems in faulted conditions," said Luka Strezoski, a doctoral student at Case Western Reserve University and an author on the paper.

For traditional grid systems, the power alternates currents, resulting in a fault if the current encounters a pathway without resistance. A short-circuit fault can produce power at 30 times the intended rate, which can result in power disruption, fire and damage to equipment.

"The biggest difference between modern distributed generators and traditional alternating current machines [if a fault occurs]... is that the short-circuit currents of modern distributed generators are controlled, whereas traditional alternating current machines lose their control," Strezoski said. It may sound safer to maintain control, but the difference causes several problems.

Using the current range calculated by a short-circuit computation, engineers established the relay limits for the whole system. While the computation method used on traditional systems is reliable and accurate, the same computation on a distributed generation system with decentralized power dispersal is not— introducing high errors with subsequent miscalculations for the rest of the system.

"The real-time short-circuit computation needs to satisfy two necessary assets: it needs to be fast, and it needs to be highly accurate," said Strezoski.

Researchers were able to make real-time operating decisions quickly based on an algorithm capable of predicting every possible future and past state of a system. Researchers eventually combined that algorithm with another algorithm capable of modeling traditional and modern power systems. The method was used in four large-scale simulations, accurately optimizing the system in 74 milliseconds.

The researchers are currently investigating how to predict and correct other fault types in addition to developing possible control strategies for emerging distributed energy resources.

The study is published in IEEE/CAA Journal of Automatica Sinica (JAS), a joint publication of the IEEE and the Chinese Association of Automation.