Aaron Cramer

Department Chair, TVA Professor of Electrical and Computer Engineering, Lewis Honors Faculty

The SCOPE Laboratory has contributed to a variety of projects in simulation, control, and optimization of power and energy systems as described below.

Current Projects

Analysis and design techniques for effective resource utilization, ONR

Advances in shipboard power systems are creating new opportunities to apply energy to meet the mission needs of the warfighter, but the growing complexity of such systems is creating new challenges for the control systems that must govern them. Improvement in analysis and design techniques will improve resource utilization, allowing the system to operate more efficiently and/or with greater performance.

The proposed research seeks to advance the metric-based evaluation of control system performance by addressing two primary objectives:

1. Vignette-based statistical characterization of control system performance and
2. Characterization of control system states with respect to alternative uses using optimal-control-based analysis.

Contributions in these areas will immediately improve the capability of control system evaluation and will ultimately lead to new techniques for the development of control systems for complex, multi-mission systems. The approach for addressing these objectives includes the development of statistical metrics based on performance of a system over a range of representative operational vignettes, the development of multi-mission valuation of control-system states, and the integration of control-system state evaluation into mission-based optimal control for evaluation of engineering state capability.

The proposed analysis and design techniques can be used for electric warship power system control. The performance of candidate control system concepts can be analyzed, and these types of analyses can be used for requirements specification. The techniques can also be used to improve the design of such control systems, which may reduce the overall engineering cost associated with shipboard power system control. This effort will advance a systematic framework for evaluating the interaction of equipment sizing and placement, mission requirements, and control strategies, which will be necessary in order to field capable multi-mission platforms.

Novel axial flux ultra-high polarity and high-frequency electric machines for wide band gap power electronic drives, NSF (with Dan Ionel)

Electric motors account for more than 60% of the electricity consumed and electric machines and associated power electronic drives represent a multi-billion dollar industry. The research will develop fundamental knowledge and innovative concepts for high-efficiency and high-performance electric machines and drives through a synergetic combination of transformational designs, multiphysics analysis, and the latest developments in power electronics, including wide band gap devices. The project will train graduate and undergraduate research students, lead to engineering teaching and training curriculum development, publically disseminate the results, and support STEM middle and high school outreach activities and increased efforts to attract students, including women and minorities, to higher education in science and engineering.

Raising the fundamental operating frequency for electrical machines results, in principle, in increased power density, provided that the typical challenges of higher losses, lower material utilization, and more complicated constructions, which are specific to conventional designs, can be overcome. The research will provide innovative solutions in this respect and study two novel axial flux permanent magnet machine topologies, which are best fitted for ultra-high number of poles and operation with high fundamental frequency, ensured through controlled supply from power electronics with wide band gap devices. One construction, suitable for high-speed operation, employs a coreless stator with an innovative continuous-wave phase winding arrangement in multiple layers. Another construction, suitable for low-speed direct drive operation, employs special rotors and innovative ferromagnetic-core stators with a winding pattern such that the stator coils and teeth are one order of magnitude lower than the number of rotor poles, a design feature that far exceeds the characteristics of known topologies. This machine also incorporates a torque magnification effect, which contributes to size reduction and efficiency increase for given power output. For two-phase machine designs, innovative hybrid H-bridge inverters comprising one leg with wide band gap devices and another leg with silicon devices are proposed for control and system integration. Computational studies include multi-physics analysis for electromagnetic, thermal, and mechanical stress, and differential evolutionary algorithms for mathematical optimization, and systematic comparison of thousands of candidate designs. Experimental studies include building prototype demonstrators and laboratory testing. The outcomes are ultra-high power density and efficient electric machine-drive systems.

Model and graph theory-based differential-evolution optimization framework for power, propulsion and energy storage systems of electric aircraft, NASA Kentucky Space Grant (NASA) (with Dan Ionel and James Lumpp)

This graduate fellowship proposal fully aligns with the NASA current mission for turboelectric and all electric aircraft. A major objective of this project will be the pioneering development of a model and graph theory based multi-objective stochastic optimization framework in order to enable lightweight, highly efficient, and reliable electric and turboelectric aircrafts. The new transformational and highly-generalized approach will enable the very topology of an electric aircraft to be a variable to be optimized through a novel differential-evolution algorithm. The proposed methodology employs a network graph domain, such that thousands of distinct candidate topologies, as determined by the optimization algorithm, can be taken into account by modifying the graph parameters. More specifically, each network graph uniquely represents a power system configuration, which is solved in order to calculate outputs including fuel consumption over a mission profile, mass, cost and reliability. As a result of the automated optimization, the system topologies that best meet the objectives will be identified. The findings from the proposed study, which will be demonstrated, in collaboration with the NASA advising team, on a MW class turboelectric aircraft power system, as well as on a fractional MW urban air mobility vehicle, will serve to establish optimum power system layouts, as well as quantify the limitations of current subsystem and component technologies. System reliability, which is of paramount critical importance in aviation, will be specifically considered as a constraint in the multi-objective optimization studies. In addition, the proposed work includes the development of a unified model-based real time condition-monitoring algorithm for power electronics converters and battery energy storage systems. This part of the work builds upon the success of last year’s NASA KY GF program, including computational models and laboratory hardware development.

Previous Projects

• Market-based control and optimal simulation techniques for small orbital satellite power systems, NASA Kentucky Space Grant (NASA)
• Market-based control of shipboard integrated engineering plants, ONR (ONR Young Investigator award)
• Foundations for engineering education in distributed energy resources (FEEDER): A distributed technology training consortium, University of Central Florida (DOE)
• Bi-directional dc/dc three port converter, WBG dc/ac drive and distributed controls for electric and hybrid airplanes, NASA Kentucky Space Grant (NASA)
• Experimental hardware system for measurement and analysis of electric power, University of Kentucky Vice President for Research
• A modular electrical power system architecture for small spacecraft, NASA Kentucky Space Grant (NASA)
• Electric power distribution system optimization in the presence of renewable distributed generation, Southeastern Center for Electrical Engineering Education
• Electric warship early design space methods incorporating dynamic energy storage, United States Naval Academy (ONR)
• Market-based power allocation with energy storage, PC Krause and Associates (NASA)
• A modular electrical power system architecture for small spacecraft, NASA Kentucky Space Grant (NASA)
• NGIPS early design space assessment, ONR

If you would like more information about any of these projects, please contact Dr. Cramer (aaron.cramer@uky.edu).

Members of the SCOPE Laboratory have published results in leading journals and presented at top conferences in these research areas. You can find details of these publications below.

Journal Papers

1. Y. Q. Zhang and A. M. Cramer, “Formulation of rectifier numerical average-value model for direct interface with inductive circuitry,” IEEE Trans. Energy Conversion, vol. 34, no. 2, pp. 741–749, Jun. 2019.
2. S. Ibrahim, A. M. Cramer, and Y. Liao, “Integrated control of voltage regulators and distributed generation inverters,” Electric Power Systems Research, vol. 169, pp. 45–52, Apr. 2019.
3. T. Lim, A. Cramer, S. Rawashdeh, and J. Lumpp, Jr., “A modular electrical power system architecture for small spacecraft,” IEEE Trans. Aerospace and Electronic Systems, vol. 54, no. 4, pp. 1832–1849, Aug. 2018.
4. S. Ibrahim, A. M. Cramer, X. Liu, and Y. Liao, “PV inverter reactive power control for chance-constrained distribution system performance optimisation,” IET Generation, Transmission & Distribution, vol. 12, no. 5, pp. 1089–1098, Mar. 2018.
5. M. Liu and A. M. Cramer, “Computing budget allocation in multi-objective evolutionary algorithms for stochastic problems,” Swarm and Evolutionary Computation, vol. 38, pp. 267–274, Feb. 2018.
6. Y. Q. Zhang and A. M. Cramer, “Numerical average-value modeling of rotating rectifiers in brushless excitation systems,” IEEE Trans. Energy Conversion, vol. 32, no. 4, pp. 1592–1601, Dec. 2017.
7. D. C. Cambron and A. M. Cramer, “A lithium-ion battery current estimation technique using an unknown input observer,” IEEE Trans. Vehicular Technology, vol. 66, no. 8, pp. 6707–6714, Aug. 2017.
8. X. Liu, A. M. Cramer, and F. Pan, “Generalized average method for time-invariant modeling of inverters,” IEEE Trans. Circuits and Systems I: Regular Papers, vol. 64, no. 3, pp. 740–751, Mar. 2017.
9. A. M. Cramer, X. Liu, and M. Liu, “Electric power distribution system optimization in the presence of renewable distributed generation,” Trans. Techniques in STEM Education, vol. 2, no. 1, pp. 11–15, Oct.–Dec. 2016.
10. Y. Q. Zhang and A. M. Cramer, “Unified model formulations for synchronous machine model with saturation and arbitrary rotor network representation,” IEEE Trans. Energy Conversion, vol. 31, no. 4, pp. 1356–1365, Dec. 2016 (Best Paper 2016-2017).
11. M. Liu and A. M. Cramer, “Genetic algorithm with integrated computing budget allocation for stochastic optimization,” Int. J. Metaheuristics, vol. 5, no. 2, pp. 115–135, Nov. 2016.
12. H. Chen, A. M. Cramer, and X. Liu, “Average-value modeling of hysteresis current controlled three-phase inverters,” Electric Power Components and Systems, vol. 44, no. 6, pp. 693–700, Mar. 2016.
13. X. Liu, A. M. Cramer, and Y. Liao, “Reactive power control methods for photovoltaic inverters to mitigate short-term distribution system voltage magnitude fluctuations,” Electric Power Systems Research, vol. 127, pp. 213–220, Oct. 2015.
14. E. A. Paaso, Y. Liao, and A. M. Cramer, “Dual-layer voltage and var control approach with active participation from distributed generations,” Electric Power Components and Systems, vol. 43, no. 8–10, pp. 854–865, May 2015.
15. E. A. Paaso, Y. Liao, and A. M. Cramer, “Formulation and solution of distribution system voltage and var control with distributed generation as a mixed integer non-linear programming problem,” Electric Power Systems Research, vol. 108, pp. 164–169, Mar. 2014.
16. S. Z. Aljoaba, A. M. Cramer, S. A. Rawashdeh, and B. L. Walcott, “Thermoelectrical modeling of wavelength effects on photovoltaic module performance – Part II: Parameterization,” IEEE J. Photovoltaics, vol. 2, no. 3, pp. 1034–1037, Jul. 2013.
17. S. Z. Aljoaba, A. M. Cramer, and B. L. Walcott, “Thermoelectrical modeling of wavelength effects on photovoltaic module performance – Part I: Model,” IEEE J. Photovoltaics, vol. 3, no. 3, pp. 1027–1033, Jul. 2013.
18. A. M. Cramer, B. P. Loop, and D. C. Aliprantis, “Synchronous machine model with voltage-behind-reactance formulation of stator and field windings,” IEEE Trans. Energy Conversion, vol. 27, no. 2, pp. 391–402, Jun. 2012.
19. A. M. Cramer, S. D. Sudhoff, and E. L. Zivi, “Metric optimization-based design of systems subject to hostile disruptions,” IEEE Trans. Systems, Man, and Cybernetics, Part A: Systems and Humans, vol. 41, no. 5, pp. 989–1000, Sep. 2011.
20. A. M. Cramer, S. D. Sudhoff, and E. L. Zivi, “Performance metrics for electric warship integrated engineering plant battle damage response,” IEEE Trans. Aerospace and Electronic Systems, vol. 47, no. 1, pp. 634–646, Jan. 2011.
21. A. M. Cramer, S. D. Sudhoff, and E. L. Zivi, “Evolutionary algorithms for minimax problems in robust design,” IEEE Trans. Evolutionary Computation, vol. 13, no. 2, pp. 444–453, Apr. 2009.

Conference Papers

1. A. Flath, III, A. Cramer, and J. Lumpp, “Mathematical programming based approach to modular electric power system design,” in IEEE Aerospace Conf., Big Sky, MT, 2–9 Mar. 2019.
2. D. F. Opila, J. Stevens, and A. Cramer, “The role of future information in control system design for shipboard power systems,” in Int. Ship Control Systems Symp., Glasgow, UK, 2–4 Oct. 2018.
3. V. Rallabandi, J. Wu, A. M. Cramer, D. M. Ionel, and P. Zhou, “Optimal design of outer rotor switched reluctance machines for direct drive rim installations,” in 2018 IEEE Energy Conversion Congr. and Expo., Portland, OR, 23–27 Sep. 2018.
4. Y. Q. Zhang and A. M. Cramer, “Unified model formulations for synchronous machine model with saturation and arbitrary rotor network representation,” in 2018 IEEE PES General Meeting, Portland, OR, 5–9 Aug. 2018, paper invited for presentation based on IEEE Trans. Energy Conversion paper.
5. D. Lawhorn, V. Rallabandi, A. Cramer, and D. Ionel, “Distributed propulsion power electronics drive-train architectures for hybrid and solar electric vehicles and airplanes,” in AIAA/IEEE Electric Aircraft Technologies Symp., Cincinnati, OH, 12–13 Jul. 2018.
6. A. W. Flath, III, A. M. Cramer, and Y. Q. Zhang, “Market-based control as a paradigm for power system control,” in Advanced Machinery Technology Symp. 2018, Philadelphia, PA, 27–29 May 2018.
7. S. Ibrahim, A. Cramer, and Y. Liao, “Integrated distribution system optimization using a chance-constrained formulation,” in 49th North American Power Symp., Morgantown, WV, 17–19 Sep. 2017.
8. Y. Q. Zhang and A. M. Cramer, “Market-based control of electric ship power systems,” in 2017 IEEE Electric Ship Technologies Symp., Arlington, VA, 15–17 Aug. 2017.
9. A. Flath, III, A. M. Cramer and X. Liu, “Control system modeling in early-stage simulation for cyber vulnerability assessment,” in 2017 IEEE Electric Ship Technologies Symp., Arlington, VA, 15–17 Aug. 2017.
10. E. Oh, D. Opila, J. Stevens, E. Zivi, and A. Cramer, “Ship design and evaluation using multi-period power flow,” in 2017 IEEE Electric Ship Technologies Symp., Arlington, VA, 15–17 Aug. 2017.
11. X. Liu, A. M. Cramer, V. Rallabandi, and D. M. Ionel, “Switching Frequency Selection for Ultra-Low Inductance Machines,” in IEEE Int. Electr. Machines and Drives Conf. 2017, Miami, FL, 21–24 May 2017.
12. A. Omosebi, Z. Li, X. Gao, N. Holubowitch, J. Landon, A. M. Cramer, and K. Liu, “Deionization and energy recovery in capacitive systems with inverted operation characteristics,” in Pacific Rim Meeting on Electrochemical and Solid-State Science 2016/Electrochemical Society 230th Meeting, Honolulu, HI, 2–7 Oct. 2016.
13. X. Liu and A. Cramer, “Three-phase inverter modeling using multifrequency averaging with third harmonic injection,” in 2016 IEEE Energy Conversion Congr. and Expo., Milwaukee, WI, 18–22 Sep. 2016.
14. X. Liu and A. Cramer, “Hybrid position observer for brushless dc motor drives with improved noise immunity,” in 2016 IEEE PES General Meeting, Boston, MA, 17–21 Jul. 2016.
15. A. M. Cramer, E. L. Zivi, and J. D. Stevens, “Light-weight, early-stage power system model for time-domain simulation,” in Advanced Machinery Technology Symp. 2016, Philadelphia, PA, 25–26 May 2016.
16. M. Liu, A. M. Cramer, and B. P. Loop, “Automated stability evaluation of interconnected systems for spacecraft power systems” in 2016 IEEE Aerospace Conf., Big Sky, MT, 5–12 Mar. 2016.
17. A. M. Cramer, X. Liu, Y. Zhang, J. D. Stevens, and E. L. Zivi, “Early-stage shipboard power system simulation of operational vignettes for dependability assessment,” in 2015 IEEE Electric Ship Technologies Symp., Alexandria, VA, pp. 382–387, 22–24 Jun. 2015.
18. J. D. Stevens, A. M. Cramer, D. Opila, and E. L. Zivi, “Operational vignette-based electric warship load demand,” in 2015 IEEE Electric Ship Technologies Symp., Alexandria, VA, pp. 213–218, 22–24 Jun. 2015.
19. A. Omosebi, X. Gao, J. Landon, K. Liu, A. Cramer, and Z. Li, “Bi-directional dc/dc converter coupled with capacitive deionization for efficient desalination,” in 2014 Electrochemical Society and Sociedad Mexicana de Electroquímica Joint Int. Meeting, Cancun, Mexico, 5–10 Oct. 2014.
20. F. Pan and A. Cramer, “Reduced-order multifrequency averaging in naturally sampled PWM converters,” in 2014 IEEE Energy Conversion Congr. and Expo., Pittsburgh, PA, pp. 3010–3015, 14–18 Sept. 2014.
21. X. Liu and A. Cramer, “Inverter power control to support distribution system voltage variability mitigation,” in 2014 IEEE Energy Conversion Congr. and Expo., Pittsburgh, PA, pp. 689–694, 14–18 Sept. 2014.
22. H. Chen and A. M. Cramer, “Average-value modeling of hysteresis current controlled brushless dc motor drives,” in 2014 IEEE Transportation Electrification Conf. and Expo., Dearborn, MI, 15–18 Jun. 2014.
23. S. Z. Aljoaba, A. M. Cramer, and B. L. Walcott, “Active optimal optical filtering of wavelengths for increasing the efficiency of photovoltaic modules,” in 2014 IEEE 40th Photovoltaic Specialists Conf., Denver, CO, pp. 1329–1334, 8–18 Jun. 2014.
24. A. M. Cramer and L. Holloway, “Electric power systems education for multidisciplinary engineering students,” in 2014 ASEE Ann. Conf., Indianapolis, IN, 15–18 Jun. 2014.
25. A. M. Cramer, F. Pan, H. Chen, and E. L. Zivi, “Modeling and simulation for early-stage quantitative assessment of medium-voltage dc power system protection schemes,” in Electric Machines Technology Symp. 2014, Philadelphia, PA, 28-29 May 2014.
26. X. Liu, A. M. Cramer, and Y. Liao, “Reactive-power control of photovoltaic inverters for mitigation of short-term distribution-system voltage variability,” in 2014 IEEE PES T&D Conf. and Expo., Chicago, IL, 14–17 Apr. 2014.
27. A. M. Cramer, B. P. Loop, and D. C. Aliprantis, “Synchronous machine model with voltage-behind-reactance formulation of stator and field windings,” 2013 IEEE Power and Energy Society General Meeting, Vancouver, BC, 21–25 Jul. 2013, paper invited for presentation based on IEEE Trans. Energy Conversion paper.
28. A. M. Cramer, H. Chen, and E. L. Zivi, “Shipboard electrical system modeling for early-stage design space exploration,” in 2013 IEEE Electric Ship Technologies Symp., Arlington, VA, pp. 128–134, 22–24 Apr. 2013.
29. Y. Liao, W. Fan, A. Cramer, P. Dolloff, Z. Fei, M. Qui, S. Bharracharyya, L. Holloway, and B. Gregory, “Voltage and var control to enable high penetration of distributed photovoltaic systems,” in 2012 North American Power Symp., Urbana-Champaign, IL, 9–11 Sep. 2012.
30. L. Holloway, Y.-T. Cheng, D. G. Colliver, A. Cramer, P. A. Dolloff, B. Gregory, J. G. Groppo, Jr., Y. Liao, S. M. Lipka, J. Neathery, J. M. Parker, V. Singh, J. Sottile, T. R. B. Taylor, and R. Andrews, “A multidisciplinary power and energy engineering program,” in 2012 ASEE Ann. Conf., San Antonio, TX, 10–13 Jun. 2012.
31. S. Z. Aljoaba, A. M. Cramer, and B. L. Walcott, “Experimental characterization of a thermo-electrical model of photovoltaic modules,” in 2012 38th IEEE Photovoltaic Specialists Conf., Austin, TX, pp. 3380–3385, 3–8 Jun. 2012 (best student presentation finalist).
32. A. M. Cramer, D. C. Aliprantis, B. P. Loop, “Advanced generator modeling in medium voltage dc power systems,” in Electric Machines Technology Symp. 2012, Philadelphia, PA, 23–24 May 2012.
33. A. M. Cramer, E. L. Zivi, and S. D. Sudhoff, “Modeling and simulation of an electric warship integrated engineering plant for battle damage response,” in Proc. 2011 Grand Challenges on Modeling and Simulation Conf., The Hague, Netherlands, pp. 230–237, 27–30 Jun. 2011.
34. S. Z. Aljoaba, A. M. Cramer, and B. L. Walcott, “Thermo-electrical modeling of light wavelength effects on photovoltaic cell performance,” in 2011 37th IEEE Photovoltaic Specialists Conf., Seattle, WA, p. 192–, 19–24 Jun. 2011.
35. S. D. Sudhoff, B. P. Loop, J. Byoun, and A. M. Cramer, “A new procedure for calculating immittance characteristics using detailed computer simulations,” in IEEE Power Electronics Specialists Conf., 2007, Orlando, FL, pp. 901–908, 17–21 Jun. 2007.
36. B. N. Cassimere, R. R. Chan, J. Cale, A. M. Cramer, and S. D. Sudhoff, “Evolutionary design of electromagnetic and electromechanical devices,” in IEEE Electric Ship Technologies Symp., 2007, Arlington, VA, pp. 150–157, 21–23 May 2007.
37. A. M. Cramer, S. D. Sudhoff, and E. L. Zivi, “Performance metrics for electric warship integrated engineering plant battle damage response,” in IEEE Electric Ship Technologies Symp., 2007, Arlington, VA, pp. 22–29, 21–23 May 2007.
38. A. M. Cramer, R. R. Chan, S. D. Sudhoff, Y. Lee, M. R. Surprenant, N. S. Tyler, E. L. Zivi, and R. A. Youngs, “Modeling and simulation of an electric warship integrated engineering plant,” in SAE Power Systems Conf., New Orleans, LA, 7–9 Nov. 2006.

If you would like more information about any of these publications, please contact Dr. Cramer (aaron.cramer@uky.edu).

Aaron Cramer

Aaron Cramer is the leader of the SCOPE laboratory at the University of Kentucky. Dr. Cramer is the Kentucky Utilities Associate Professor of Electrical and Computer Engineering and the director of graduate studies for the electrical engineering graduate programs in the Department of Electrical and Computer Engineering in the College of Engineering at University of Kentucky.

Teaching

• Average teaching evaluations of 4.79/5
• Outstanding Electrical and Computer Engineering Teacher Award in 2014 and 2018
• Tau Beta Pi Most Outstanding Professor in the College of Engineering Award in 2016
• Undergraduate and graduate courses in electric machinery, power electronics, and power systems

Research

• Simulation, control, and optimization of power and energy systems
• 60 publications, including 21 journal papers
• $2,572,719 in total funding at University of Kentucky, including $929,281 as principal investigator
• Office of Naval Research Young Investigator in 2015
• Advised 7 Ph.D. students and 18 M.S. students
• Currently advising 1 Ph.D. student

Service

• Member of University Senate and University Senate Council and chair of Senate Academic Programs Committee
• Faculty associate of Power and Energy Institute of Kentucky
• Previous member of search committee for multiple positions
• Previous member of College of Engineering Research Team, Office of Research Web Focus Group, First-Year Engineering Program Engineering Computing Committee
• Previous departmental representative for International Teaching Assistant Language Screening and College of Engineering Graduate Recruitment Weekend.
• Editor of IEEE Trans. Energy Conversion and guest editor for special sections
• Treasurer for IEEE Electric Ship Technologies Symp. 2019
• Technical program co-chair for IEEE Int. Electric Machines and Drives Conf. 2017
• Reviewer for numerous journals, conferences, and research sponsors
• Senior member of IEEE and member of IEEE Power and Energy Society

Alumni

Alumni

• If you find your information missing or out of date, please contact Dr. Cramer (aaron.cramer@uky.edu) to update your information.