Hybrid approach optimizes grid

Hybrid Approach Optimizes Grid
Jie Liu, a Ph.D. candidate in industrial engineering, recently received IBM’s Ph.D. Fellowship Award, one of the industry’s most competitive sources of funding for Ph.D. students. Credit: Christa Neu

The modern "smart" city, says Jie Liu, is a web of networks that should run like a healthy, well-tuned circulatory system.

This is especially true, says Liu, a Ph.D. candidate in industrial engineering, for the power grid, which directs electricity from to consumers. Electric power should flow through the grid in a way that utilizes as efficiently as possible the resources that are used to produce the power.

This streamlined flow, says Liu, is made possible by machines that process large quantities of data in real time and make optimal decisions.

Liu and his colleagues, Martin Takáč, assistant professor of industrial and systems engineering and Liu's Ph.D. adviser, and Jakub Mareček of IBM Research, have made considerable progress in solving optimal power flow problems in the past two years.

For his contributions, Liu recently received IBM's Ph.D. Fellowship Award, one of the industry's most competitive sources of funding for Ph.D. students.

A power system, say the researchers, often contains many power stations, which produce , and a central entity, called the transmission system operator, which coordinates the production and transmission of power.

The goal of the operator is to transmit electricity from power stations to customers with maximum efficiency and minimal losses. If a wire carries too much electric current, it incurs losses and could overheat, possibly causing a blackout.

Operators of power plants and transmission systems cannot choose where power will flow, say the researchers, because power follows the laws of physics. But they can decide where to generate power and how to set the transformers along the way.

The physics of the alternating-current model of flows makes these decisions difficult to make, says the group. But they correspond to polynomial optimization problems (POPs), which are a hot topic today in the field of mathematical optimization.

Until recently, researchers could apply the so-called Newton method to POPs to obtain a solution quickly. Or, as suggested by Mareček and his colleagues, they could solve a sequence of surrogate problems to obtain the best possible solution.

The second approach often took too long, though, causing Liu, Mareček, and Takáč to seek conditions under which one could switch from the surrogate problems to the Newton method without obtaining solutions that would be wrong. Using recent developments in numerical algebraic geometry, the group has developed such conditions and designed methods to test them efficiently. One can therefore solve the surrogate problems quickly and, when it is safe, switch to the Newton method.

"This revolutionizes the field of polynomial optimization," says Mareček.

The first in a series of papers by the group, "Hybrid Methods in Solving Alternating-Current Optimal Power Flows," has just been accepted in IEEE Transactions on Smart Grid. That article is coauthored with Alan Liddell of the University of Notre Dame.

Liu enrolled at Lehigh in 2013 after completing his M.S. in mathematics from the State University of New York at Buffalo. He holds a B.S. in mathematics from Nankai University in Tianjin, China.

Prior to receiving the IBM Ph.D. Fellowship, Liu received the Dean's Doctoral Assistantship and Dean's Fellowship from Lehigh's P.C. Rossin College of Engineering and Applied Science, the Gotshall Fellowship from Lehigh, and the American Express Machine Learning Contest Award.

At Lehigh, Liu is part of a research group called Optimization and Machine Learning (OptML), which includes Takáč; Katya Scheinberg, the Harvey E. Wagner Endowed Chair Professor of Industrial and Systems Engineering; and Frank Curtis, associate professor of industrial and .

Students in the OptML group receive support to present their work at international conferences and are encouraged to do industrial internships. Liu has worked with Siemens Corporate Research, Mitsubishi's Electricity Research Laboratories (MERL), and Argonnes National Laboratory near Chicago, outside of IBM.

"These are amazing opportunities," he says. "These are different companies, totally different. These internships connect us to industry. They give us the chance to do something we're interested in and to learn new knowledge at the same time.

"The professors in our group are very supportive. They really help us learn how we can contribute and make an impact."


Explore further

Optimizing power networks for tomorrow's smart cities

More information: Hybrid Methods in Solving Alternating-Current Optimal Power Flows. arXiv:1510.02171 [math.OC] arxiv.org/abs/1510.02171
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Jul 14, 2017
"Electric power should flow through the grid in a way that utilizes as efficiently as possible the resources that are used to produce the power."


Not really. The electric grid is there to serve its customers' needs primarily, and the efficient utilization of resources is a secondary parameter which may be reached after everyone's got the electricity they need and want, in that order of importance.

The smart grid, smart city, etc. ideas all seem to come from central planning engineers and bureaucrats that see the delivery system as the point to optimize at the expense of the users, who are forced to adopt technologies and measures that may often be inconvenient or require other adjustments - they're operating from the point of view that the people serve the system, instead of the system serving the people.

Jul 14, 2017
They're operating from the point of view that they own the system, and if you don't want what they're selling you can go get it yourself.

You are choosing to ignore the fact that if the system fails due to overloading, nobody will get power at all. The system operators will be held at fault if there's a blackout because their job is to manage it so that doesn't happen.

Since you know that, it seems you are making that choice just to take a swipe at "central planners and bureaucrats."

There's a reasons libertarians live in the dark.

Jul 15, 2017
"You are choosing to ignore the fact that if the system fails due to overloading, nobody will get power at all. "


On the contrary. That's my entire point: if the operators choose to build a system that only works by limiting and rationing power to its customers, they've failed their purpose.

The problem here is that central planners and bureaucrats are forcing this "solution" on everyone, whether its greedy utility operators trying to cut too much cost, or politicians trying to force unstable and unreliable power generation onto the grid to get kickbacks from the industry.

-"if you don't want what they're selling you can go get it yourself."


Way to blame the victims. The power company has a monopoly, and forcing its customers to go off-grid because of poor service is again a failure in the books of an utility that's meant to serve the public.

Jul 16, 2017
No one has "failed their purpose" by creating a better system. The old system is a monopolistic - single source system that creates massive amounts of pollution. This plant eats 40,000 tonnes of coal per day - with associated air pollution, coal ash, and mining destruction. https://atomicins...-burner/ Monopolies are bad. Single source systems are bad. Air, water, land pollution are bad. I am in favor of a multi source, distributed, low carbon, low pollution system. Once again I am struck by the need to write a thesis, on why progress cannot happen...

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