Power electronics and the world's largest machine

Rolando Burgos in the CPES High-Power Laboratory

Rolando Burgos in the CPES High-Power Laboratory. The research center is adding more high-power capability and willsoon inaugurate its new medium voltage network for research testing.

Power electronics technology has successfully enabled energy and cost savings in many low- and medium-power applications. Recent advances in materials and modularization have poised the technology to achieve similar savings for high-power applications — including the power grid, which is sometimes called the world's largest machine.

Rolando Burgos joined ECE as an associate professor last fall to help lead the high-power efforts in the Center for Power Electronics (CPES). Power electronics is expected to interface two-thirds of all electrical loads connected to the grid leading to tremendous energy savings potential, he says.

Working closely with industry members in the Renewable Energy and Nano-grid (REN) mini-consortium at CPES, Burgos helped map out a new high-power research direction, involving three major topics: developing new modular, multi-level power converters for both AC and DC power distribution systems; investigating new dynamic interaction aspects triggered by the control system of grid-connected power converters — which could lead to unstable operating conditions; and the exploration of DC distributed systems for both low and medium voltage.

Integrating renewable resources into the grid

In AC power systems, the group is investigating distribution systems that have a high penetration ofrenewable energy sources. "The big question is, how can power electronics help integrate these renewable resources into the grid in an efficient, reliable, safe, and sustainable way" he says.

Part of the answer will involve the development of advanced Flexible AC Transmission System (FACTS) devices, according to Burgos. "We believe enhanced FACTS devices can enable the integration of larger amounts of renewable energy," he says."They can increase the power transmission capability, help direct the power flow and optimize the control of the whole power system, especially under strong power fluctuations and intermittency which are inherent to renewables." Integrating the next generation of FACTS devices will involve more than developing appropriate power converters, but also the use of new synchronization and control methods maximizing their true potential.

"It's a difficult problem," he says. Renewable energy sources like solar and wind are subject to powerfluctuations and intermittency. "They come and go. Their integration carries the risk of driving the grid into unstable conditions and eventually a full voltage collapse."

The challenge for renewable energy is how to tap the abundant resources that are often located in remote areas far from consumption centers. Burgos cites another power electronics solution that is taking care of this — high voltage direct current (HVDC) transmission, which represents the most efficient way to transport large amounts of energy over long distances.

"How much renewable energy you can integrate into the grid is ultimately the main issue that needs to be addressed," he says.

DC distribution systems yield energy savings

Burgos and the CPES team are also involved with developing DC distribution systems for residential and higher-power distribution systems. DC distribution is gaining much support in recent years, with supporters saying that the energy-saving potential of DC distribution is significant given the elimination of redundant AC/DC and DC/AC conversion stages typical of present-day AC distribution systems.

Developing power electronics technology for both AC and DC distribution means that power electronics will be useful in patching and updating the current AC grid, or in establishing new DC grids. "We don't know what will happen with powergrids," Burgos says. "Will the newer technology replace the old grid or operate alongside" He points out that cellular telephone networks operate alongside the landlines, even as they replace existing wired networks. The future power grid, or super grid, israpidly evolving, although in an unknown direction. "Only time will show which structure will prevail, but either way, it will be a power electronics-based network," he believes.

While power electronics holds great promise for future generations of power grids, research in high-powerelectronics presents a new set of challenges due to the hazardous testing conditions and the lack of test equipment capable of operating in such environments. "This makes the research more difficult in terms of laboratory facilities," according to Burgos.As a result, CPES is slowly transitioning towards high power testing, and it will soon conduct its inaugural measurements using a 4160 VAC medium voltage network. "There are very few universities with a medium voltage lab at present, and we are proud to be one of them," he adds.

Spotlight on New Faculty Members

Rolando Burgos joined ECE after serving three and a half years at ABB Corporate Research as principal scientist. He also held an adjunct position as an associate professor of ECE at N.C. State University. Burgos received a B.S. in electronics engineering in 1995, an electronics engineer professional degree in 1997, an MSEE in 1999, and a Ph.D. in 2002,all from the University of Concepcion, Chile.

Power Engineers 2.0

In applying power electronics to power transmission and distribution systems, power electronics engineers are venturing into a body of knowledge that has traditionally been the domain of power systems engineers. Today it is becoming more common to hear both groups asking the same questions and working on the same problems. This is a natural progression from integrating an enabling technology in an established complex system.

The Department of Energy (DoE) is encouraging universities to promote the integrations and expose engineers to both sets of knowledge. "The power engineers of tomorrow will face exponential growth in demand for electricity, plus the management of renewable energy, and of smart-grid technology," says Rolando Burgos. "DoE is concerned that the requirements of power engineers are increasing at the same time that many power engineers and power engineering professors are retiring. Tomorrow's power systems engineers need both sets of skills."

Under a Virginia Tech College of Engineering effort, Burgos is co-advising a graduate student with Yaman Evrenosoglu, a power systems faculty member. The student, Chi Li, is working on FACTS devices and their synchronization and controls methods. "At Virginia Tech, we have very strong programs in both areas and educating students across these bodies of knowledge will ensure that our graduates can take leadership positions in the field," he says.