A smaller, more efficient grid-tied power converter garners top prize for researchers

ECE News

Claire Hettinger, ECE ILLINOIS
1/12/2016

Story Highlights

  • Graduate student Shibin Qin, along with Professor Robert Pilawa, won the Best Paper Award at the IEEE Workshop on Control and Modeling for Power Electronics (COMPEL) Conference in Vancouver, Canada.
  • The team was able to invigorate and reduce the size of grid-connected power converters with their research.
  • The key innovation was a new circuit architecture and digital control method that enabled the power filtering to be accomplished with less overall power conversion.

ECE ILLNOIS researchers' new technique for invigorating and reducing the size of grid-connected power converters is broad: it could affect anything that connects to the grid can use this technique, including computer servers, solar inverters, grid storage, and electric vehicles.

Shibin Qin accepting the best paper award at the COMPEL conference.
Shibin Qin accepting the best paper award at the COMPEL conference.
For their work, graduate student Shibin Qin, along with Professor Robert Pilawa-Podgurski, won the Best Paper Award at the IEEE Workshop on Control and Modeling for Power Electronics, COMPEL, Conference in Vancouver, Canada.

“We were able to greatly reduce the size of  grid-connected power converters," Pilawa said. "So if for instance, you are trying to fit an onboard charger into an electric car, or an inverter on the back of a solar panel, there is only so much weight and volume you can allow for your power converter. Our new converter is now six times smaller. That’s a big benefit."

Students Yutian Lei, Christopher Barth, and Wen Chuen Liu also contributed to the paper, “Architecture and control of a high energy density buffer for power pulsation decoupling in grid-interfaced applications.”

The work demonstrated in the prize-winning paper is a new power decoupling buffer architecture. Many things we plug into the power outlet require power decoupling: LED lights, battery chargers for laptops, phones, and more. Rooftop solar panels also require them. Power decoupling buffers are widely used in grid-tied power converters, as well.

Robert  Pilawa-Podgurski
Robert Pilawa-Podgurski
“What we came up with was a way of using a few more semiconductors and a much smaller capacitor filter together with a more sophisticated control technique to achieve the same level of power decoupling, but in a much smaller size," Pilawa said. "Another significant advantage of the new method is that the overall efficiency has also been greatly improved, where we have measured an efficiency of more than 99.5 percent."

A high efficiency is of particular importance when the overall power converter size shrinks, since any loss is dissipated as heat, which becomes more and more difficult to remove as the physical size is reduced.

“Compared to current state-of-the-art solutions, we have demonstrated a 3-5 times reduction in power losses, which directly leads to cooler electronics, with longer lifetime," he said.

The key innovation was a new circuit architecture and digital control method that enabled the power filtering to be accomplished with less overall power conversion, he said. Smaller overall power conversion leads to lower power losses, and increased efficiency.

With less power conversion, the passive components (inductors and capacitors) can also be made smaller, because their physical size is proportional to how much power they process. A key enabling technology of this work is a sophisticated digital control method that keeps the system operating smoothly, both during regular operation, and during startup, shutdown, and during any faults.

Shibin Qin
Shibin Qin
“Shibin did an outstanding job coming up with a very innovative and clever control algorithm to make this new idea work in practice," Pilawa said. "Given this, I was particularly happy to see this new concept be awarded with a best paper prize at COMPEL, which is the top control conference in power electronics."

The research could have broad implications, Qin said.

“From an engineering application perspective, this technique can make many things we plug into the wall smaller, more efficient, and more reliable,” he said.

In addition to the typical consumer electronics such as laptop chargers and TVs, their work could also have implications for renewable energy, especially in making electronics more reliable.

“If you can put this in a solar panel that will last 25 years, we can build a much more reliable circuit,” Qin said.

Qin and Pilawa’s paper introduced a fundamentally new concept and a sophisticated control implementation with a significant academic contribution, but also a design for practical applications, Qin said.

“We are able to show in an actual hardware prototype this significant reduction in size, and improvement in efficiency,” Qin said. “We included a strong execution of the idea, which I think was very much appreciated.”

Texas Instruments supported the research team, and its members used a TI micro-controller to implement the control algorithm and drive the electronics, Pilawa said.

“We have demonstrated to Texas Instruments what you can do with such an advanced controller in this important application,” he said. “The results were so exciting that we are now working with TI to see whether we can further modify a controller to achieve even better results.”

In addition to financial support of the research, TI provided industry-relevant feedback to ensure that many practical concerns were addressed.

"Our partners at TI - Shamim Choudhury, Mike DiRenzo, Brian Carpenter, and Anand Dabak – offered great feedback on both the micro-controller capabilities and product considerations in monthly conference calls,” Pilawa said.

TDK, which is a capacitor manufacturer, also supported the team’s work by providing capacitor samples and engineering know-how through Product Manager Mike Cannon (BS Ceramic Engineering '93). TDK is interested in this research because it could open up new markets for its higher reliability capacitors, Pilawa said.

“Right now we’ve demonstrated this concept,” Pilawa said, “some future work is studying the optimal size cost benefit, how to optimize it, and then it’s a matter of applying it to the right applications.”

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