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.