Pilawa earns PELS young engineer award
For almost any electronic applications — from solar to smartphones to electric vehicles and beyond — power converters are essential. In a smartphone, small dc-dc converters are integrated into the circuitry: one boosting voltage for the display, for instance, another for the audio. To eke more functions out of the phones without necessitating mid-day charging, more efficient, yet small and inexpensive power converters are needed.
Today people know how to make highly efficient power converters, but then they become quite large and quite expensive, said ECE Assistant Professor and ITI researcher Robert Pilawa-Podgurski. Our contribution has really been to make efficient power converters that are also very small and cheap. ... We have to always keep in mind that we want someone to use it. ... That's how we kind of judge our success.
To address this size-and-cost problem for power converters, Pilawa and his students have worked on increasing the speed at which the converters pulse on and off. This is the so-called switching frequency — a means of regulating voltage. At the faster speeds, smaller energy storage components can be used: smaller inductors or capacitors, smaller transformers.
Yet the increased switching frequency and smaller components come at a cost. Every time you switch you lose a little energy, Pilawa said. So a lot of our techniques are trying to minimize that loss that happens when we switch.
In part, this requires algorithmic innovations, like recent developments in his lab for dithering digital ripple correlation control, which leverages existing ripples in solar photovoltaic power converters to achieve inexpensive and efficient energy extraction, about 10 times more accurate than the previous state-of-the-art approaches. At the same time, even the algorithmic solutions must be demonstrated with physical hardware, which Pilawa and his students build in the lab.
It's a very interdisciplinary field, Pilawa said. You have to be a good circuit designer. ... You have to understand the material properties. You certainly have to be hands on and build things, but at the same time, you have to code the control algorithms. On top of that you have to understand the electromagnetics that govern your inductors, transformers, and capacitors. Now that I'm in the field, that's what I like about it, that you are exposed to so many different aspects of electrical engineering.
Another design solution that Pilawa and his students have been exploring is the use of capacitors, rather than inductors, in dc-dc converters. These components are used to temporarily store charge before releasing it at a new voltage. For the same power rating, capacitor-based converters can be smaller, although there is more power loss. Some of Pilawa's recent work has focused on a hybrid, coupling a capacitor-based converter with a small inductor to effectively gain the size and efficiency benefits of both.
Pilawa initially delved into power-converter research as a graduate student, drawn by an interest in renewable energy. I quickly discovered that whether it's solar, wind, thermoelectric, any of these new energy sources ... all of those involve a power converter, he said. I found it to be a great opportunity to ... work with any existing renewable energy sources and also ideally be part of the new ones that are coming.
As the price of the solar cells has plunged in recent years, Pilawa indicated that the converters and other power electronics are becoming a substantial part of the overall system cost. Accordingly, several hardware implementations that he and his students have demonstrated pertain to solar power production. I wouldn't call it a bottleneck, but they are really becoming a critical thing that we have to keep innovating, Pilawa said.
Like Pilawa, the members of his lab — there are currently 12 graduate students and several undergraduates — often come with an interest in renewable energy, although not exclusively. Quite a few of them are also just interested in power electronics in general, Pilawa said. It's fun. You can actually see it, touch it, build it.
As for the PELS Award, Pilawa credits the hard work of his students for the success. He will officially accept the award in September at the IEEE Energy Conversion Congress and Expo, the main societal conference, which will be held in Pittsburgh.
At that meeting — as with their highly referenced journal, IEEE Transactions on Power Electronics — the society facilitates technical innovations ranging from the effective use of power electronic components to the application of circuit theory and design techniques to the development of analytical tools for efficient conversion, control, and condition of electric power.
As I look back at past recipients, it's a very impressive list, Pilawa said of the award. Past winners ... are now very well-recognized experts, sort of the top people in our area.
As a matter of fact, the list includes Pilawa's graduate research adviser, David Perreault, who is now the associate department head of electrical engineering and computer science at the Massachusetts Institute of Technology. And as the innovations in power converters keep coming from Pilawa, and as students continue to be trained in his lab, that lineage of young, successful engineers is guaranteed to keep growing.
Editor's note: media inquiries should be directed to Brad Petersen, Director of Communications, at bradpillinois [dot] edu or (217) 244-6376.