Solutions for power system vigilance and resilience
Electricity powers so much of modern life that it’s hard to imagine a world without it. From keeping the lights on to energizing phones and laptops to controlling indoor climate and fueling transportation, a reliable flow of electricity is essential to daily living.
ORNL researchers have long been engaged in research to protect the critical infrastructure that generates and delivers electricity. Today the work has a new sense of urgency as grid-focused cyberattacks are on the rise and utilities tackle the challenge of integrating intermittent renewable energy with traditional power plants.
It is not an easy task. Over time, the grid has been stitched together out of disparate, individually owned generation, transmission and local distribution equipment.
“There was no original blueprint of what the future grid would look like,” said Tom King, director of ORNL’s Sustainable Electricity Program. “So now the challenge is how to add new intelligent technologies and integrate them into these older legacy systems.
“Historically we’ve used a Band-Aid approach, building add-ons to protect the network. But what we need is to have security and resilience designed into the system as we modernize the grid.”
ORNL’s grid work largely falls into four areas: monitoring, modeling, controls and advanced components.
The first—monitoring—relies heavily on the lab’s history in sensors and measurements. ORNL has developed sensors that can monitor the essential elements of the grid, from the first generation of electricity to its end use in businesses and homes.
For example, ORNL scientists have developed low-cost sensors that monitor dissolved gases in transformers. An excess of acetylene gas in a transformer’s insulation oil may indicate electrical arcing. With this knowledge, operators can better assess equipment and reroute power before faults occur and cascade into blackouts. The lab is also developing sensors printed on flexible substrates that can measure current and voltage on electrical equipment ranging from high-voltage transmission lines to heating, ventilation and cooling systems at businesses and homes.
In perhaps the lab’s most ambitious monitoring program, researchers led by UT-ORNL Governor’s Chair Yilu Liu have developed a low-cost sensing system, GridEye, consisting of frequency disturbance recorders plugged into 120-volt outlets. The compact recorders transmit real-time data on the grid’s electrical frequency and voltage angle, monitoring the wide-area grid in much the way that an electrocardiogram monitors the cardiac system.
The sensors have been installed at 250 locations in North America. The system was recently refined as a mobile device, with an app known as the Mobile Grid Analyzer that enables operators to monitor the grid in the field using smart phones and tablets.
“It’s the only system in the U.S. that gives a complete view of what’s happening across the grid in North America,” Liu said. “It’s important to be able to see all areas of the grid, not just one region. What may happen in Florida will affect systems as far away as the Dakotas.”
“These next-generation sensors create situational awareness,” King said. “Operators can track and catch trends about the condition of their assets and can take action more quickly.”
Wide-area situational awareness is also important as more renewable generation sources such as solar panels and wind turbines are added to the grid, because of their intermittent nature, Liu added.
The data can be fed into simulations of the grid that can help industry better prepare for events such as storm damage or cyberintrusion as well as long-term trends like shifts in supply and demand. That’s the second area of ORNL’s grid work: modeling and simulation.
As more smart devices such as high-fidelity sensors are installed on the grid, the data flowing back to operators will grow exponentially.
“You’ll be able to see events like transients on the system that indicate anomalies, or better understand the condition of grid components so you can make better predictions,” King explained. “That’s the value proposition for operators.”
ORNL’s expertise in mathematics and computer simulation has driven modeling work that can, for instance, guide industry in how best to deploy new protection relays, which can automatically reroute power around faults like downed power lines.
Modeling can also give a wider view of the grid to help electric system coordinating agencies, industry and the government gain a better understanding of the grid’s interdependencies. ORNL and other national labs are working to model all the underpinnings of the connected grid, analyzing elements like fuel supply (such as the natural gas pipeline network), telecommunications systems, the placement and health of transmission and generation assets, and the placement of microgrids where they can be networked to support the bulk power system.
ORNL has used two of its own inventions to aid modeling and simulation work. A low-voltage test bed called SI-GRID safely tests hardware and software components intended for high-voltage systems. A digital twin of the grid—a simulation fed by real-time information on the grid state—has also been developed to test cybersecurity solutions.
Eventually, as more intelligence is built into the grid, sensors will feed into a system that provides real-time control so that outages are not just dealt with quickly but are prevented entirely.
That’s where the third thrust of ORNL’s grid work enters the picture: software and intelligent hardware controls to introduce more automation on the grid.
Controls research includes a unique, open-source microgrid controller developed at ORNL and successfully deployed by a partner utility in two residential neighborhoods. ORNL researchers have also developed transactive controls that use advanced algorithms to communicate information about power availability and market price between a consumer and the grid operator to efficiently control energy use in homes and buildings. More precise control of energy generating and consuming equipment can result in customer savings and a more resilient electricity network.
The microgrid controller helps resolve a big issue for the grid: the growing amount of electricity produced by decentralized, distributed generation sources such as solar and wind that must be integrated into the system. Using intermittent renewable generation poses a challenge for utilities accustomed to big power plants and only one-way electricity flows.
“We’re developing creative ways to integrate these local power assets and get as much benefit from them as we possibly can,” said Ben Ollis, who leads the lab’s microgrids research.
ORNL’s microgrid controller can help keep the larger grid balanced by selling its excess electricity or by supplying local customers with 100 percent of their power needs. That could happen involuntarily during a grid blackout or voluntarily in a scenario known as demand response. In times of peak demand, the utility will signal the microgrid controller with a price offer. If that offer is accepted, the microgrid will island itself in a practice known as load shedding, Ollis explained.
“Microgrid controls are about taking everything you have to consider on the larger grid and shrinking it,” Ollis said. “You have to consider demand as well as supply and be able to serve your local users on a moment’s notice” if the microgrid is islanded.
In addition, the transactive controls being developed at ORNL could harness the energy consumption of a fleet of buildings to help balance a grid’s electrical loads by, for example, preheating or precooling work and living spaces during off-peak hours without sacrificing occupant comfort.
“We want a system that’s not necessarily reactive, but proactive,” said Rick Raines, director of the Electrical and Electronics Systems Research Division at ORNL. “We want to build capabilities so that we can move ahead of where the threat of disruption might be as the operating environment changes.”
To encourage the most resilient grid possible, ORNL researchers are looking at ways to embed computing power at the grid edge. In this approach, grid controls are decentralized so that devices like protective relays and sensors can continue to function even if parts of the network are compromised and the devices cannot communicate with a control center.
“When you have these distributed, disparate and integrated networks, if you wait until something is communicated to a central location to act, you’ve already lost the battle,” Raines said.
Such a future will rely on artificial intelligence so that the trillions of data points flowing into the control system can be swiftly analyzed and addressed.
“We can use machine learning initially as forensics to analyze past events,” explained Mark Buckner, leader of the Power and Energy Systems Group at ORNL. “Then, as the system learns, it creates a predictive model that says, ‘This is what I’m expecting to see if I do this,’ and when that bears out, it builds confidence in the model. If you extend that model into smart automated controls, you have a system that understands precursors based on past events—so that the system can be proactive when those same events happen in the future.”
King added, “Artificial intelligence and machine learning will be important for the operational and controls side, but also for the cybersecurity piece of protecting the grid. We want to get to a system that can immediately determine whether an event is due to a nefarious actor attempting to disrupt the system, or that a car struck a power pole.”
One of ORNL’s largest grid projects seeks to secure the underpinning for these controls. The DarkNet project creates an architecture with underused optical fiber to construct a private, secure network for grid communication. The key objective is to get grid controls and data transfer off the public internet.
The fourth thrust of ORNL’s grid research focuses on supporting the grid of the future with devices such as power electronics, energy storage, intelligent relays and other advanced components that will enable a smart, resilient and secure system. These devices receive signals from the controls side and take action.
For instance, energy storage is a vital element for the grid. Storing energy for later use is essential to the integration of intermittent renewable power sources and to provide resilience if the grid is compromised. ORNL scientists have developed several technologies in this area: a system that stores electricity mechanically in pressurized water vessels; components for a low-cost reduction-oxidation—or redox—flow battery that stores a large amount of electricity in a cross between a conventional battery and a fuel cell; and a system that deploys used electric vehicle batteries for grid-level energy storage.
Power electronics enable the integration of energy storage, solar panels, vehicle chargers and other essential elements into the grid while ensuring reliability of service. ORNL scientists are creating inverters using heat-tolerant silicon carbide materials and low-cost 3D printing methods for both high-voltage transmission systems and lower-voltage local utility systems. These electronics accommodate the multidirectional power flow required for distributed energy and can mimic the operation of conventional power plants to maintain grid frequency—what operators refer to as the balance between electricity supply and demand.
Changes to generation sources also mean that the grid must respond rapidly to frequency fluctuations. ORNL’s protective relay research is focused on developing intelligent relays that can monitor and automatically respond to grid frequency changes, clearing faults faster to ensure a stable grid. This is a change from past industry practice, in which relays were often installed in the field with a static setting—referred to as “set-it-and-forget-it.”
To prepare for these changes, electric industry partners have increasingly turned to the national labs, working hand in hand to ensure that technological solutions are thoughtfully designed and with a low enough cost to be adopted broadly for the best system-wide outcome. The interdependent grid, after all, is just that—disruption of one part of the network can affect end-users hundreds or thousands of miles away.
“You cannot just implement all these changes quickly. There are already huge hardware investments on the grid,” Liu said. “It is our biggest challenge today to make the system resilient without adding another $5 trillion on. We need to figure out a way to make the grid resilient without gold-plating it.”
That’s where industry partnerships come in. Partners who can help guide research for the best outcome are essential for success.
ORNL has worked with multiple utilities, equipment vendors, industry research organizations and academic partners to test new technologies. Many of the sensing and control technologies developed by ORNL, for instance, have been tested on the system of the Electric Power Board of Chattanooga, Tennessee. EPB’s all-fiber-optic network provides an ideal living laboratory to test smart grid technologies—including a recent test of quantum key distribution. QKD leverages the inherent randomness of quantum mechanics to authenticate and encrypt information, potentially creating a system of grid communication that cannot be hacked.
Southern Company, one of the largest utility operators in the nation, worked directly with ORNL scientists to successfully test microgrid controls in two residential neighborhoods in Alabama and Georgia. The Tennessee Valley Authority has also been a long-standing partner to ORNL in developing generation and transmission technologies, in addition to supplying the bulk of the lab’s own power.
Some of ORNL’s advancements in monitoring have been accomplished in collaboration with another local partner, CURENT, a National Science Foundation engineering research center at the University of Tennessee. CURENT—the Center for Ultra-Wide-Area Resilient Electric Energy Transmission Networks—was the first engineering research center to be cofunded by the NSF and DOE. ORNL and UT, through CURENT, codeveloped the GridEye and Mobile Grid Analyzer. CURENT likewise works closely with industry partners to help direct its research efforts.
“If we don’t have industry partners, our research will go nowhere,” King said. “Developing key partnerships with utility companies and vendors is critical to getting these ideas to the marketplace.”