21 January 2020

No more long hours of blackout

Under the leadership of Siemens Corporate Technology, a research project funded by the U.S. Department of Energy will develop innovative solutions for situational awareness, distributed control during cyber attacks or natural disasters, and autonomous restoration after power outages. The power system will become more resilient to cyber attacks and natural disasters with the technologies developed while also helping to minimize the hazards for utility employees.

Severe storms can cause massive outages in the United States

In September 2018, Hurricane Florence cut off the power supply for hundreds of thousands of people in the state of North Carolina for several days. Between 2017 and 2018, around 25 million people in the US experienced power outages for more than one hour. Compared to the European power grid where much of the power line infrastructure is buried underground, the power grid in the US is more vulnerable to natural disasters due to the pervasiveness of overhead power lines. They stretch over thousands of miles, even supplying remote areas such as densely forested mountains.

“When a tree branch touches a power line, a chain reaction that takes entire regions off the grid can start, as was the case for the major power outage in the Northeastern United States in 2003,” explains Ulrich Münz, a researcher at Siemens Corporate Technology in Princeton, New Jersey.

He will lead the AURORA project (Autonomous and resilient operation of energy systems with renewables) in partnership with the National Renewable Energy Laboratory (NREL), Columbia University School of Engineering and utility company Holy Cross Energy. Over the next three years, the AURORA project team will develop a range of functions and assistance systems to make power systems in the US more resilient. Depending on the state of the power grid, the researchers will split the grid into several microgrids to supply electrical loads either individually or collectively. Microgrids are playing an increasingly important role as power generation becomes more decentralized. Siemens has developed the SICAM™ Microgrid Controller (MGC) and the Spectrum Power™ Microgrid Management System (MGMS) for this reason and has used them in several research, pilot and commercial projects all over the world.

Cyber attack or a branch on the line?

In the first stage of the project, Siemens is working with Columbia Engineering to find out how network operators can detect critical events faster and identify their root causes. The aim is to detect line failures due to physical incidents as well as cyber attacks on substations or control centers. “We compare the real behavior in the power system with its digital twin and want to find out how to quickly identify the cause of a malfunction,” explains Münz. In addition, preventive measures are investigated to prepare the power grid for predictable disruptions. “If the connecting line to a remote town leads through a wild fire area, the town can be prepared for a failure of this line by starting local generation units such as diesel generators,” explains Münz. In this way, a power outage in a remote town could be prevented. In the second stage, the research project will investigate how the power supply can be maintained after cyber attacks on the power system control center or the communication network. According to Münz, the aim is “to ensure that in the event of a control center failure, the microgrids coordinate with each other in order to continue supplying power to critical loads such as hospitals”. In the AURORA project, researchers from Siemens and NREL are developing new control methods for coordinating the microgrids, which automatically balance the decentralized generation and the load among each other in such a way that no further failures occur.

Power restoration bottom-up approach

In the future, it will no longer take several days to restore power after a complete outage such as the one caused by Hurricane Florence. Currently, the power system must be manually restored by first gradually connecting the large conventional power plants to the grid and then connecting loads such as cities and industrial plants. In many cases, this is a very time-consuming process due to human intervention including the risk mitigation processes that must be followed to protect the workers. In AURORA, Siemens and NREL are investigating a revolutionary bottom-up system restoration approach, how the many decentralized generation units that exist today could restart the grid by automatically reconfiguring and collectively stabilizing the grid after a blackout. “We are developing special control functions that make an autonomous black start within the microgrids possible,” says Münz. These control functions can be installed in smart inverters of residential solar power systems, batteries, or wind turbines that successively build microgrids to provide electricity to streets and small towns. A key secondary benefit to autonomous black start is that it decreases the risk exposure to the utility workers. Solar power plant of Holy Cross Energy, one of the research partners in Colorado. In the back 13,400 ft Mount Sopris in the Rocky Mountains. Each research partner contributes their expertise to AURORA: Columbia University has experience in detecting cyber attacks on power grids; NREL understands how renewable energy resources contribute to the stability and reconstruction of power grids, and how to optimize these resources in real time; Siemens contributes its expertise in microgrid control technology and digital twins of power grids. To test the new algorithms and assistance systems, the research consortium is building two laboratory-scale demonstrators: One will be located at Siemens Corporate Technology in Princeton. “This is where we will test our newly-developed smart inverter control functions,” says Münz. All developed technologies will be implemented in a larger demonstrator at NREL, where they will have to prove their capabilities in realistic scenarios. For this purpose, the power system of Holy Cross Energy is simulated in real time in the demonstrator and extended by two laboratory-scale microgrids consisting of 50 smart inverters from Siemens. This power grid will then be divided into microgrids controlled by SICAM MGC and coordinated by Spectrum Power MGMS. The newly developed functionality will be implemented in the smart inverters as well as MGC and MGMS, and then tested in various scenarios.

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