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Research Staff

NREL's distributed grid integration research staff work to strengthen and diversify the electric power system through NREL's Power Systems Engineering Center.

Photo of James Cale

James Cale, Distributed Energy Systems Integration Group Manager

Ph.D., Electrical Engineering, Purdue University
M.S., Electrical Engineering, Purdue University
B.S., Electrical Engineering, MS&T

Dr. James Cale is an expert in the field of power electronics and electrical machine modeling and simulation. His background and research interests are in the areas of high-penetration PV integration on the electric grid, control of power electronic devices, microgrids, electromagnetics, and multi-objective optimization. James currently manages the Distributed Energy Systems Integration group at NREL.

Prior to joining NREL, James worked as a member of technical staff at Advanced Energy, where he simulated and designed controls for advanced utility-scale PV inverters.

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Nathan Ainsworth, Engineer

Ph.D., Electrical Engineering, Georgia Institute of Technology
B.S., Computer Engineering, Purdue University

Nathan joined NREL in 2014 after finalizing his Ph.D. work at Georgia Institute of Technology with a joint appointment as a Grid Innovation Leaders (GIL) Fellow at Oak Ridge National Laboratory. Prior to pursing his doctoral degree and following the completion of his bachelor's degree, he joined the staff of DRS Test and Energy Management, LLC, as a control and product development engineer for a line of power management systems for U.S. military vehicles. Nathan's experience includes a multidisciplinary background in embedded systems, distributed control theory, power electronics, and power and energy systems.

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Ravel Ammerman, Research Associate

Ph.D., Engineering Systems (Electrical), Colorado School of Mines
M.S., Electrical Engineering (Power and Control), University of Colorado
B.S., Engineering (Power and Instrumentation Specialty), Colorado School of Mines

Dr. Ravel Ammerman is a teaching professor, specializing in energy systems, in the Electrical Engineering and Computer Science Department at Colorado School of Mines. He also works part time as a research associate at NREL. Ravel has over 30 years of combined teaching, research, and industrial experience. His research interests include distributed grid integration, arc flash hazard analysis, electrical safety, computer applications in power system analysis, and engineering education.

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Tom Basso, Senior Engineer

M.S., Engineering Thermodynamics, Applied Analysis, State University of New York, Stony Brook
B.E., Engineering Science, State University of New York, Stony Brook

Tom started at NREL when it was the Solar Energy Research Institute in 1980. Tom is the codes and standards principal investigator for the DOE Office of Electricity NREL Electricity Program and DOE EERE NREL photovoltaics. He is an internationally recognized NREL professional and subject matter expert for electricity grid integration and interconnection of renewables and Smart Grid standards and related activities.

Tom contributes to program development, conducts analytical engineering and subcontract management, and is representative and vice chair for IEEE Standards Coordinating Committee and, its IEEE 1547™ interconnection and IEEE 2030™ smart grid activities. Tom also represents renewables in International Electrotechnical Commission standards groups. Previously at NREL, Tom conducted outdoor accelerated-weathering tracking system testing of PV modules, and was NREL project manager for the NREL PV Advanced R&D Project Management work package.

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Murali M. Baggu, Senior Engineer

Ph.D., Electrical Engineering, Missouri University of Science and Technology, Rolla
M.S., Electrical Engineering, University of Idaho, Moscow
B.Tech., Electrical and Electronics Engineering, Kakatiya University College of Engineering, Warangal, India

Murali Baggu is an expert in distribution system modeling and visualization for Volt-VAr control/optimization and mitigation of distribution grid issues arising due to high penetration of PV. His research interests include grid integration of renewables systems (wind and PV), energy storage system integration, distributed energy resources, distribution automation, power systems, power electronics, electric machines and drives.

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Robert Butt, Jr., Senior Engineer

M.S., Electrical Engineering, University of Arizona, Tucson
B.S., Electrical Engineering, University of Arizona, Tucson
Registered Professional Engineer, Arizona, Colorado, Missouri, Montana, New Mexico, Oregon, Washington, and Wyoming

Bob Butt supports the assessment and deployment of renewable technologies into electric power systems at NREL through site assessments, software simulations, development of options/cost analyses, and formal reports. Bob has 30 years of experience in medium- and low-voltage power distribution, including planning and studies, design, construction, testing, and commissioning of power system electrical infrastructure, electrical equipment, and buildings.

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Sudipta Chakraborty, Senior Electrical Engineer

Ph.D., Engineering Systems, Electrical, Colorado School of Mines
B.E., Electrical Engineering, Bengal Engineering College, India

Sudipta joined NREL in 2007. His recent research activities include development of advanced and modular power converters for renewable and distributed energy resources, development and testing of new smart electrical distribution modeling, and hardware-in-loop validation techniques. His other specialty areas include power electronics and control for microgrid systems; inverter and hybrid vehicle grid integration testing; control and optimization (classical, neural network, fuzzy logic); variable frequency drives; and active filtering.

Sudipta is the primary author of two published software copyrights and two provisional patents on modular power electronics. Various other intellectual properties developed by him on PV inverter hardware and software are currently under NREL-DOE review for future patents and copyright applications. Sudipta is a senior member of the IEEE and currently serving in IEEE-IES technical committees on power electronics and renewable energy systems. He worked as one of the guest editors for the IEEE Transactions on Industrial Electronics special section on renewable energy systems. Recently Sudipta co-edited a book titled "Power Electronics for Renewable and Distributed Energy Systems: A Sourcebook of Topologies, Control and Integration" (Springer).

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Mike Coddington, Senior Engineer

B.S., Electrical Engineering, Colorado State University
Master Electrician, Electrical Contractor, State of Colorado

Michael Coddington is a senior electrical engineering researcher and principal investigator in distributed grid integration. His work at NREL focuses on the integration of distributed generation systems to the electric distribution system, with a focus on high-penetration PV concerns and solutions. He has authored and collaborated on dozens of technical reports and whitepapers focusing on integrating distributed generation systems onto the grid. Michael is also active in standards and codes development, is a senior member of the IEEE, was secretary of IEEE 1547.6, and is a member of the UL1741 Standards Technical Panel.

Prior to NREL, Michael worked in the electric utility sector for 20 years in distribution planning and key account management.

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Julieta Giraldez, Microgrid Engineer III

MS, Electrical Engineering, Colorado School of Mines
Bachelor of Technical Engineering in Mining, Energy Resources and Explosives, Madrid School of Mines (UPM), Spain

Julieta Giraldez works at NREL as an electrical engineer in the Distributed Energy Systems Integration grop where she is currently involved in microgrid and smart grid related projects. She is an important contributor to the Marine Corps Air Station Microgrid project, and is now leading several other microgrid projects such as the US Air Force Academy Microgrid.

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Peter Gotseff, Senior Research Technician

M.S., Electrical Engineering, Colorado School of Mines
M.S., Environmental Engineering, Colorado School of Mines
M.S., Mechanical Engineering, Portland State University
B.S., Engineering Physics, University of Colorado

Peter joined NREL in 2001 as a research technician at the Solar Radiation Research Laboratory supporting solar resource measurement activities. In 2010 he transitioned to the Distributed Energy Systems Integration group, where he provides support with solar resource inputs to electrical system models as well as continued support of the solar resource group. His recent activities include evaluation of improved processing methods on satellite based solar resource data and creating solar resource input datasets for distribution system models designed to evaluate system impacts due to PV variability.

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Kevin Harrison, Senior Engineer

Ph.D., Energy Engineering, University of North Dakota
M.E., Energy Engineering, University of North Dakota
B.S., Electrical Engineering, University of Rochester

Kevin began working at NREL as a summer intern, returning for two more summers until he was hired as a senior engineer in charge of all experimental research for the renewable electrolysis task. At NREL, he leads the technical aspects of the Renewable Electrolysis task and Wind-to-Hydrogen demonstration project where the objective is to improve the efficiency and reduce the capital costs of renewable hydrogen systems. Dr. Harrison also leads the International Energy Agency, Task 24, Subtask B researching opportunities for wind-to-hydrogen system improvements. He has also participated in NASA's Regenerative Fuel Cell Task Team researching the feasibility of such devices for lunar missions.

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Andy Hoke, Engineer III

M.S., Electrical Engineering, University of Colorado
B.A., Engineering Physics, Dartmouth College

Andy joined the Distributed Energy Systems Integration group in 2014 having worked most recently as a Research Assistant at the University of Colorado, Boulder, as well as a Graduate Research Participant at NREL. His experience includes research in the fields of power electronics hardware and controls, advanced inverter design and testing, battery system optimization, distribution system modeling for renewables integration, microgrid modeling, and power hardware-in-the-loop experimentation. Andy is currently an electrical engineering Ph.D. candidate at the University of Colorado, Boulder, and has authored several journal articles, conference proceedings, and technical reports.

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Randy Hunsberger, Senior Engineer

M.S., Civil Engineering, Building Systems Program, University of Colorado
B.S., Mechanical Engineering, Oakland University
B.A., English, Oakland University

Randy has been working as a mechanical engineer since 1987 and has worked in renewable energy since 1999. He spent three years working at NREL's National Wind Technology Center while working on his master's degree. He then spent eight years in consulting, working primarily on biomass heat and power projects around the country, before returning to NREL in 2010. In addition to biomass projects, Randy has been involved in studies for landfill gas, solar, geothermal, and wind energy projects. In the biomass arena, Randy has worked on a variety of projects, including heating, power production, combined heat and power, anaerobic digestion of animal manures and municipal solid waste, biomass densification, and waste-to-energy.

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Brian Johnson

B.S., Physics, Texas State University
M.S., Ph.D., Electrical and Computer Engineering, University of Illinois at Urbana

Brian was awarded a National Science Foundation Graduate Research Fellowship in 2010. His research interests are in nonlinear control theory, power electronics, distributed generation, and renewable energy systems.

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Blake Lundstrom, Electrical Engineer

B.S., Engineering, Colorado School of Mines
M.S., Electrical Engineering, Colorado School of Mines

Blake has been employed at NREL since 2009. His research is focused on integration of distributed and renewable energy resources into the electric distribution system. Specifically, his research involves distribution system modeling, advanced power electronics development, modeling and evaluation of microgrid systems, and advanced modeling and evaluation methods for grid interconnection systems using real-time hardware-in-the-loop techniques. Blake also plays a key role as a member of the operations team for NREL's Energy Systems Integration Facility. He has taught courses in electrical engineering as an adjunct faculty member at Colorado School of Mines. Blake is a member of IEEE and a registered engineering intern in the State of Colorado.

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Barry Mather, Electrical Engineer

Ph.D., Electrical Engineering, University of Colorado
M.S., Electrical Engineering, University of Colorado
B.S., Electrical Engineering, University of Wyoming

Barry's research in the Distributed Energy Systems Integration group is focused on the integration of high penetration levels of PV generation in to the distribution grid. He works with host utilities to model, simulate, and measure the impacts of PV integration on their system. PV inverters with advanced functionality specifically developed for mitigating the impacts of distributed PV integration are also being modeled and tested in both lab and field environments. He is also involved an effort to characterize the variability of PV generation through high-speed data acquisition of an operating PV plant. His research interests also include distribution system modeling, advanced anti-islanding algorithms, micro-inverters, and digital control of power electronic systems. Barry is a member of IEEE, the Power Engineering Society, and the Power Electronics Society.

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Peter McNutt, Senior Engineer

M.S., Electrical Engineering, University of Colorado
B.S., Electrical Engineering, University of Colorado

Peter has been working with NREL since 1997 as an electrical engineer. He has experience inspecting, testing, and commissioning PV systems. He has worked with utilities and system integrators to monitor the impact PV systems have on distribution systems. He is also the chair of the IEEE SCC21 PV battery working group, responsible for writing and coordinating national standards. He started at NREL conducting performance and reliability testing of PV arrays and systems. He has provided technical support for local, national, and international PV systems and laboratories. He has assisted in the design of PV/hybrid power systems to power reverse-osmosis water purification plants, remote outpost science stations, and off-grid PV systems. Peter is a registered Professional Electrical Engineer in the State of Colorado and a senior member of IEEE.

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Austin Nelson, Engineer

M.S., Electrical Engineering, University of Wisconsin — Madison
B.S., Electrical Engineering, University of St. Thomas, St. Paul, Minnesota
B.A., Physics, University of St. Thomas, St. Paul, Minnesota

Austin joined NREL in 2014, having spent the previous two years as a research assistant at the University of Wisconsin – Madison in the Power and Energy group within the Electrical and Computing Engineering department. Prior to that, Austin worked on new product design, compliance testing, and failure analysis for residential and commercial grid-tied solar inverters at PV Powered/Advanced Energy. His master's thesis work focused on the design of a new microgrid testbed for future distributed energy research at the Wisconsin Energy Institute. Austin is a licensed Professional Engineer.

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Amy Osten, Project Manager

PMP, Project Management Institute
Supply Chain Management, Master Planning of Resources, Detailed Scheduling and Planning, APICS
B.S. (in progress), Organizational Leadership, Colorado State University

Amy joined NREL in 2014 as a Project Manager for the Distributed Energy Systems Integration group. Prior to joining NREL, she worked as the Global Service Contract Manager/O&M Manager at Advanced Energy, where she managed a department that monitored and maintained over 350 MW of solar power. Her experience includes managing complex R&D and engineering programs for DC, low-/mid-frequency, and high-voltage power systems along with solar PV inverters through manufacturing product release and offshore transfers. Amy has a proven track record of developing business strategies and operational excellence in the thin film and solar energy industries. She has experience in utilizing Six Sigma methodologies and was selected to participate in Advanced Energy's 2012 Leadership Summit. Amy is a Mile High Chapter member of the Project Management Institute.

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Bryan Palmintier, Senior Engineer

Ph.D., Engineering Systems, MIT
Mechanical Engineering, Stanford University
M.S., Aero/Astro Engineering, Stanford University
B.S., Aerospace Engineering, Georgia Tech

Bryan joined NREL in 2013 as a DOE/EERE SunShot Postdoctoral Fellow. His research interests include high-penetration distributed solar; interactions among renewables, buildings, vehicles, and the grid; stochastic analysis for power systems; hardware-in-the-loop testing; impacts of operational flexibility on unit commitment and planning; and co-simulation of distribution and transmission systems. Prior to NREL and his Ph.D., Bryan worked with the Energy and Resources Team at Rocky Mountain Institute; consulted with Energy Solutions in Oakland, CA; spent six years on adjunct faculty and research staff at Santa Clara University's Robotics Systems Lab; and worked as a staff energy researcher at Stanford University. He also teaches mountaineering and leadership for the National Outdoor Leadership School and has supported fish research at McMurdo Station in Antarctica, built satellites for Stanford's Space Systems Development Lab, and designed hybrid rockets at the Naval Center for Space Technology.

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Annabelle Pratt, Senior Engineer

Ph.D., Electrical Engineering, Oregon State University
M.S., Electrical and Electronic Engineering, University of Stellenbosch, South Africa
B.S., Electrical and Electronic Engineering, University of Stellenbosch, South Africa

Annabelle joined NREL in 2014 with 14 years of industrial research and development experience, most recently as a research engineer for the corporate research and development division of Intel Corporation. During her tenure at Intel, Annabelle worked in the areas of automated energy management, microgrid energy management, advanced digital control of voltage regulators, direct current power delivery for data centers, and high-efficiency server power supplies. Prior to Intel, Annabelle spent five years as a design engineer and project manager at power conversion equipment manufacturer Advanced Energy.

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Siddharth Suryanarayanan

Ph.D., Electrical Engineering, Arizona State University
M.S., Electrical Engineering, Arizona State University
B.E. Electrical and Electronics Engineering, Madras University, India

Sid Suryanarayanan holds a primary appointment at Colorado State University as an Assistant Professor in the ECE department, a joint appointment at NREL. His research interests are in the area of modern electric power systems, with specific focus on design, operation, and economics of finite-inertia systems; applications of cyber-physical systems to the electricity domain; and integration of renewable energy systems to electric grids.

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Hongyu Wu, Postdoctoral Researcher

Ph.D., Systems Engineering, Xi'an Jiaotong University, China
B.S., Power and Energy Engineering, Xi'an Jiaotong University, China

Hongyu joined NREL in 2014, having worked most recently as a senior research associate at the Robert W. Galvin Center for Electricity Innovation at the Illinois Institute of Technology in Chicago, Illinois. His experience includes stochastic modeling and optimization of large-scale power systems, high penetration renewable energy applications, and smart grid applications.