Energy Systems

Electricity is the lifeblood of the modern world. Everything from phones and computers to electric vehicles and the international space station use electricity. Usually, the form that electricity is in when it is generated is not the same form when it is being used. The equipment that converts electrical energy from one form to another is called power electronics. My research focuses on making power electronics more efficient, smaller, cheaper, higher performing, and more reliable.

Kilby Labs Research

I was fortunate to be able to participate in several interesting research and development projects while working in Kilby Labs. Here are a few general areas of exploration:

Graduate School Research

I examined new control techniques and power conversion architectures that will improve the performance and efficiency of direct current (dc) systems. My disseration focuses on three main areas:

Ph.D. dissertation word cloud
Ph.D. dissertation word cloud

Differential Power Processing

One of the key concepts introduced in my dissertation is called differential power processing (DPP). This simple approach seeks to improve efficiency and reliability by avoiding energy conversion in the first place. Instead of focusing on optimizing the components, control, etc. of the power converters themselves, a system level perspective is taken. The goal is to reduce the total losses in the system.

How is this possible? The orthogonality lies in the system architecture. Instead of having multiple, cascaded energy conversion stages (as is common), elements (power sources or loads) are connected together in series, and differential converters provide the difference in current between series elements. It turns out that the power converter topologies that can be applied are well known. Circuits used to actively balance the energy stored in battery packs are good candidates. (An analogous approach can also be used for elements connected in parallel.) This technique can be applied to many applications: solar photovoltaic panels/cells, LED lights and displays, computer server power delivery, data centers, microprocessors, and many more.

Subpanel differential converter
Experimental subpanel solar photovoltaic differential converters

Why is it called "differential" power processing? Good question. In many ways, differential power converters work like the differential in an automobile. A differential in your car enables your tires to rotate at different speeds while power is supplied by the same engine/driveshaft. This provides a smooth ride during turns without your wheels sliding. More generally, a differential enables two devices (e.g. wheels) to operate with independent conditions (e.g. rotating speed) by managing the difference. Differential power converters have the same purpose but are used in electrical energy systems. A fun, old school video below explains how a differential works. (I suggest you skip to about 1:50.)

Converter Augmentation

Fast response to sudden, large changes in the load of a converter is often desireable. Many digital circuits powered by voltage regulators would be damaged if their supply voltage was not kept within a narrow band. The buck converters commonly used in this application have fundamental limits to how quickly they can respond to transients. To overcome this barrier, buck converters can be augmented with additional energy paths that are designed to only operate when the load changes drastically and suddenly. A picture of a hardware prototype that explored this technique is shown below.

augmented buck converter
Augmented buck dc-dc converter
Big thanks to Micah Sweeney for designing the PCB.

Master's Thesis

The research project I did for my masters thesis explored multiple module dc-dc converters. The goal is to have a modular power system that can be implemented in a distributed fashion. I introduced local control and power ratings-based load sharing in my masters thesis. A word cloud of part of my thesis is shown below.

Masters thesis word cloud
Masters thesis word cloud

Undergraduate Research Assistants

At Illinois I had the privilege of mentoring undergraduate students who worked with me on research projects. It's a win-win situation for the grad student and the undergrads. The grad student get assistance with their research and learn how to lead a team of students in solving engineering problems. Undergraduates are exposed to the research world and get hands-on experience with some cutting edge technology. This report from the Grainger CEME center describes a few experiences. Below is a list of students who I have worked with.

Former Research Assistants

Publications

For an up-to-date listing of my publications, I suggest you check my Google scholar page. Hopefully the Google bots will keep things in order but take it with a grain of salt because I've noticed some errors/omissions in the past.

Pradeep Shenoy

Energy Systems Engineer

Texas Instruments
Dallas, TX

linux
Résumé (updated April 2015)