Sandia National Laboratories, together with New Mexico State University, is developing algorithms that they hope have the potential to create a self-healing grid.
The researchers say that by creating a library of algorithms they can code those algorithms into grid relays so that an electric system can quickly restore power to as many hospitals, grocery stores and homes as possible before grid operators can begin repairs or provide instructions.
“The ultimate goal is to enable systems to self-heal and form these ad hoc configurations when things go really bad,” Michael Ropp, Sandia electrical engineer and the project lead, said in a statement. “After the system is damaged or compromised, the system can automatically figure out how to get to a new steady-state that provides power to as many customers as it possibly can; that’s what we mean by ‘self-healing.’ The key is that we’re doing it entirely with local measurements, so there is no need for expensive fiber optics or human controllers.”
Ropp envisions an electrical grid of the future with more renewable energy sources, such as rooftop solar panels and wind turbines, and banks of batteries, many of which will have the ability to form microgrids that can island power around hospitals, water treatment plants, and other critical infrastructure if the main grid is down. The Sandia project aims to enable such microgrids to automatically heal themselves when damaged and connect with one another to share power and serve as many customers as possible.
Those microgrids would need to automatically perform critical functions such as balancing energy production with energy consumption and reconfiguring if part of the system becomes damaged or unavailable.
To achieve this in microgrids using power inverters, operators must install expensive high-speed communications that can be unreliable during disasters and vulnerable to cyberattacks. “The purpose of this project,” Ropp said, “is to support self-healing using only the measurements that each individual device can make, reducing cost while increasing reliability.”
One key function that microgrids with lots of inverters need to do is to shut off a few customers when the demand for electricity becomes larger than the supply, the Sandia researchers said.
In grids powered by natural gas, coal or nuclear power plants, existing relay algorithms can detect a drop in frequency caused by a demand-supply imbalance and disconnect power to portions of the grid. But when inverters designed to power microgrids are used, they could be programmed with an algorithm that would decrease voltage to tell relays when to disconnect power to less vital customers.
The Sandia researchers are also working on a solution to the problem of what to do when a power line that normally is at the end of the system has to move more current than it is rated for. They came up with a Morse-code-like method where an overloaded line relay modulates the voltage by opening and closing in a specific pattern, and the relays for lower-priority customers can detect this pattern and disconnect themselves until the line is no longer overloaded.
Ropp said that he and his team would like to work with manufacturers of line and load relays to incorporate their library of algorithms into the companies’ products, first to test them in a hardware-in-the-loop testbed and then possibly in real life at test facilities such as Sandia’s Distributed Energy Technologies Laboratory or at a similar medium-voltage facility at New Mexico State University.
“We definitely want this to become something that people can really use, especially low-income communities that can’t afford fiber optic communications at every single point on every single electrical circuit,” Ropp said. “You can actually get very good performance and very good resilience using our library of algorithms. And if you do have the communications, this can be a backup.”
