Power Electronics Lab Drives Renewable Energy Research

October 1, 2010

The MSU Power Electronics and Motor Drives Laboratory hums with high-energy activity as researchers here develop technologies that will keep pace with increasing consumer demand for cleaner, more efficient, and more affordable energy.

Meet two of these researchers.

Fang Z. Peng (in photo at right) professor of electrical and computer engineering and director of the laboratory, specializes in wind and solar energy research as well as hybrid electric vehicle research. An IEEE Distinguished Lecturer who has given lectures to industry in the United States and abroad, Peng has been involved with power conversion technology since his days as a PhD student. He is currently working on novel Z-source inverter technology, which potentially offers a more efficient, more reliable, and more economical conversion system than the traditional inverter in many applications.

Bingsen Wang (in photo below, left), assistant professor of electrical and computer engineering, who joined the college this year, is working specifically on methods of reliability in connecting renewable energy to the energy grid.

So while Peng’s team is developing utility interfaces for renewable energy sources and high power electronics for smart power grids, Wang’s team is focusing on improving the reliability of those power converter interfaces.

High power electronics for smart power grids is a high-demand, high-challenge area for power conversion. “In recent years, renewable energy is more in demand and there are different challenges, like complexity and the need for higher and higher power; this is the frontier for power electronics,” says Peng.

For example, says Peng, “A wind turbine generator generates electricity, but you need to convert that energy to a usable form.” And wind turbines are much bigger than they were 10 or 15 years ago, so a higher voltage and higher power converter/inverter systems are needed.

Peng goes on to explain that the power utility grid is 60 Hertz fixed voltage. But a high-power wind turbine generator generates a frequency that is variable with wind speed, so the energy that’s generated cannot be used directly. It must first be converted into electricity of the correct frequency and voltage, then sent to the utility grid, and then transmitted to the end user.

“We can utilize high power electronics to control the power flow from point A to point B to point C— reliably and efficiently,” says Peng.

However, Wang says, “Reliability is one of the biggest challenges in power electronics. This issue needs to be resolved before power electronics can be utilized in widespread applications.”

Currently, converters that use electrolytic capacitors are the most commonly used in power electronics. But by its nature, this type of component is not reliable. “My approach,” says Wang, “is to focus on some of the topologies that do not use electrolytic capacitors—such as current source converters and matrix converters.”

One aspect of Peng’s work is to make energy systems “self-healing through power electronics-based control devices,” which means that in the event of equipment failures or outages, a system would continue to provide power. Using strategically installed intelligent communications sensors, a self-healing device can deal with contingencies—outages or damage (by man or nature)—by redirecting the power flow, much like a road detour reroutes vehicular traffic during road construction.

In addition to reliability, the demand for power quality is increasing. “We need to make sure that we have the correct formats and connections, to ensure that the quality is there,” says Wang. “Customers don’t want to get voltage distortions and power interruptions.”

Wang says it’s possible that the results of his research could be utilized in real-world applications as early as 2013.

Long term, Wang is also interested in the methodology used to assess the reliability of a system. “Quantifying the reliability of the system by simply tallying the numbers and multiplying the reliability of the components—that’s not the answer. It’s the interactions among the components that are important.”

Peng’s long-term project involves working with automotive companies and suppliers in developing a new conversion circuit to control electric motors more efficiently. “Car companies envision this in use in next-generation hybrid and electric vehicles,” says Peng. He has been working with more than 30 collaborators across the United States, as well as overseas—Japan, South Korea, China, Europe, and the UK. The goal is to reduce the cost and increase the efficiency of hybrid and electric vehicles by using new power electronic circuits and developing a better battery-based energy storage system that is smaller, lighter in weight, and less expensive than those currently in use. What that means, in the long run, is that hybrid and electric vehicles would be affordable for the average consumer.

Peng and his team are also working to develop technologies that could make solar energy more cost effective.

“Researchers in the Power Electronics and Motor Drives Lab are developing many ways to make energy systems more efficient and more affordable,” says Peng. “The entire energy system— from generation, to transmission, to utilization—is not as efficient as it should be. There is still a lot of work to be done.”