Research Direction

I am broadly interested in fundamental challenges that arise when power electronics are connected in networks—both in localized contexts (e.g. modular multiphase power converters) and in highly distributed contexts (e.g. grid-interfaced renewable energy). My research explores power electronics simultaneously from a circuits and systems perspective. I leverage fundamental theory from an array of interdisciplinary domains—including decentralized optimization, networked control systems, and statistical signal processing—to develop revolutionary circuit and network architectures that are validated with industry-quality hardware prototypes. In particular, my doctoral dissertation introduced and validated the notion of system-aware power electronics, that is, power electronics that are designed in tandem and adaptively co-optimized for each other and the system they are a part of—and can offer transformative leaps in performance, efficiency, resiliency, and power density. My vision is to translate these technical innovations into practical and scalable solutions to emerging societal-scale challenges in renewable energy, electrified transportation, miniaturized and on-chip power, wireless power transfer, and energy infrastructure and distribution.

Research Highlights


Minimum Distortion Point Tracking

dc-dc converter

My Ph.D. dissertation introduces Minimum Distortion Point Tracking (MDPT): a control paradigm for interconnected dc-dc converters where switching waveforms are optimally phase shifted to minimize the total dc-bus ripple power. In a sense, MDPT generalizes the ubiquitous concept of interleaving in balanced multiphase dc-dc converters to a broad class of asymmetric input- or output-parallel connected dc-dc converters. Realizing power-quality improvement with control design implies that a drastic reduction in passive input or output filters can be achieved (10X reductions have been experimentally demonstrated to date). Minimum Distortion Point Tracking has a number of promising high-impact applications, including harmonic cancellation for dc microgrids, asymmetric dc-dc converters, and ac- and series-connected systems.

Representative Literature


Fundamental Techniques for Highly Available and Resilient Power Electronics Systems

nanogrid

The increasing ubiquity of power electronics within electric networks has introduced an array of new challenges, particularly with respect to availability, reliability, and system security and safety. Switching power converters introduce new failure points in a power distribution network. Moreover, the interactions between converters and the propagation or cascading effect of faults through an electric network remain open research questions.

The aim of this project is to develop a generalized methodology for enabling next-generation resilient and fault tolerant electric networks with high penetration of power electronics devices. Towards this end, we have introduced a suite of new algorithms, circuit techniques, and system architectures that can provide order-of-magnitude improvements in reliability and MTTF for a broad class of power electronics circuits and systems.

Representative Literature


DC Microgrids for Electrification in Emerging Regions

dc microgrid

There are currently 1.3 billion people in rural developing regions without access to electricity. This number is projected to increase despite increased grid-tied generation since there is still a significant power deficit in urban areas. Microgrids have been viewed as a viable option to provide electricity for rural areas where the cost of grid extension is prohibitive. In recent years, the falling cost of solar energy has sparked increasing interest in developing renewable methods for rural electrification. However, battery costs have not declined at the same rate as solar photovoltaic (PV) panels. Since the predominant residential usage is during night-time hours, the cost of stored electricity use is a key figure of merit. In this regard, dc microgrids have demonstrated promise as a viable method of enabling improved efficiency and scalability for off-grid systems.

In this project, we demonstrated a novel dc microgrid architecture that provides a scalable solution for rural electrification. The calculated LCOE of the dc microgrid, based on BOM costs of the proposed system and field surveys carried out by research partners, is favorable in comparison to presently deployed solar microgrid systems and also with grid power rates on certain Hawaiian islands. Moreover, a proof-of-concept prototype validated the favorable improvements in performance, efficiency, and overall robustness.

Representative Literature


Hardware-in-the-Loop for Power Electronics Systems

hardware-in-the-loop

This work has been spun-off into Typhoon HIL, Inc.

In recent years, hardware-in-the-loop (HIL) testing for power electronics has shown significant promise to serve as a comprehensive rapid prototyping platform for advanced power electronics systems. HIL testing is a technique that replaces a physical model, such as an electric vehicle, with a real-time mathematical representation that fully describes the salient dynamics of the physical model. Hardware-in-the-loop enables the testing of closed-loop device-under-test controllers under realistic operating conditions without the need to interface with a high power system. In this way, a power electronics HIL environment provides a rapid prototyping platform for the design and testing of power electronics hardware, software, and firmware. In particular, HIL tools enable: (1) accelerated testing and validation; (2) reduced testing time needed in the lab; (3) simulation of all operating points and scenarios that are difficult or impossible to recreate with a real system; (4) fault injection capability; (5) real-time access to all signals that are difficult to measure in a real system.

In 2009, we demonstrated the world's first hardware-in-the-loop platform dedicated for power electronics circuits and systems, powered by a real-time, one microsecond-time step switched linear simulator. Extensive validation and application demonstrations have validated the utility of HIL for power electronics, and in large part, laid the foundation for the power electronics HIL market that exists today.

Representative Literature


last updated: September 2018