PROGRAM AREA OVERVIEW

29. ADVANCED POWER ELECTRONICS TECHNOLOGIES

Unique applications for conversion of power, either from electrical to mechanical form or vice versa, often require unique approaches. With recent advances in power electronics and generator/motor technology, several new areas of emphasis have evolved that require innovation to achieve their expected effect on energy conversion technology. This topic solicits new materials technology for power electronics components, as well as technology for using power electronics in new applications. Grant applications must clearly show how the research effort will proceed to hardware development, fabrication, testing, and manufacture of power electronics components and devices. Grant applications are sought only in the following subtopics:

a. Advanced Power Electronics Component Materials—Over the past 10 years, advanced silicon power chips have revolutionized power conversion with the use of new power semi-conductor devices such as Integrated Gate Bi-Polar Transistors (IGBTs). Although these devices continue to improve in performance and power handling capability, there exist alternative materials that could revolutionize the performance of power electronic components. Materials such as gallium-arsenide, diamond, and, in particular, silicon-carbide (SiC) offer potentially outstanding properties for power conversion: large band-gap, high breakdown field, good thermal conductivity, and a high saturation velocity. In addition, SiC has high elastic modulus and toughness, and SiC devices can operate at temperatures up to 600^oC. Grant applications are sought to develop technology to further the use of these materials in improved power electronics devices. Areas of interest include: overcoming micro-pipe defects in SiC wafers (i.e., small tubular voids that run through the wafers in a direction normal to the polished wafer surface), innovative thermal management, advanced bonding and soldering techniques that can withstand higher temperatures, incorporating long-life capacitors in advanced SiC components, insulated metal substrates, elimination of wire bonds, automated manufacturing, and innovative packaging.

Another target of opportunity relates to the thermal properties of materials used in existing power modules. These modules are constructed by bonding the die, copper layers, substrate, and the base plate together. The whole module is then mounted on a heat sink using thermal interface materials. Unfortunately, existing thermal interface materials that can withstand high temperatures have very low thermal conductivities; in fact, the thermal interface material represents 30 to 40 percent of the total thermal resistance between the junction and the heat sink. Grant applications are sought to reduce this resistance by developing thermal interface materials with increased thermal conductivity. This requirement becomes even more important for power electronics components using SiC, which operate at higher temperatures.

For both of the above areas, special consideration will be given to grant applications that address the special operating conditions and requirements (reduced size, weight, and adverse environmental operating conditions) of electric vehicles, fuel cells, and wind turbines.

b. Permanent Magnet (PM) Drives, Motors, and Associated Power Electronics—The rapidly declining cost of rare earth permanent magnets (e.g., neodymium-iron-boron), along with their improved magnetic properties, is rapidly revolutionizing the use of permanent magnet motors and generators. Rare earth PM generators and motors offer improved power-to-weight characteristics for use in electric and hybrid vehicles, wind generators, gas turbines, gas compressors, and a wide range of other applications. Increases in the magnetic properties of the magnets would allow such devices to be applied to generators in the size range of 1 to 10 MW. Improved PM generators could be more easily designed and built as direct drive units, thereby eliminating gear boxes and oil lubrication systems while improving efficiency. These improved devices also could find use as prime movers in compressors and variable speed drives. Grant applications are sought to further improve the performance of rare earth PM generators/motors by integrating them with improved power converters. This combination would provide for variable speed operation, allowing devices such as gas turbine generators and wind turbines to run at optimum operating speeds. Areas of interest include advanced design, design tools, assembly processes, alternate fabrication materials, optimized cooling, improved reliability, electrically-insulating thermally conducting materials for cooling and thermal modeling techniques – all necessary to develop units with high power density, high efficiency, and low cost of manufacture and operation.

c. Power Electronics for Renewable Energy Applications—Improved power electronic components and circuit topologies present ever changing opportunities for improving modules for a wide range of applications in renewable energy. Power converters/conditioners and controllers could provide improved performance and integration of renewable energy technologies such as photovoltaics, wind, and hydrogen.

With respect to photovoltaics (PV), a new concept known as “AC Photovoltaic Module” could revolutionize the PV industry through improved building integration. As a first step toward commercialization, grant applications are sought to develop innovative DC-to-AC micro-inverters (in the watts range) that can be integrated into a PV panel for roof-top mounting or into other small PV-powered systems on buildings (window frames, roofs, etc.). These inverters must be rugged, able to withstand the brutal environments associated with rooftops, and must have long lifetime. Goals for the concept are to significantly reduce balance-of-system (BOS) costs, improve reliability and ease of installation, reduce the cost of the micro-inverter to the range of $0.15 to $0.30 per watt, and increase the efficiency to 94% or higher, while maintaining all Underwriters Laboratory and interconnection requirements.

Most modern wind turbines operate at variable speeds and use power electronics to condition the power, changing it from variable frequency AC to DC, and back to fixed frequency AC. A key aspect of the controller is that it is an active part of the wind turbine load-control, used to control the torque on the wind generator and rotor. The existence of the DC link within the control system offers an opportunity to use the power output of the wind turbine to directly drive an electrolyzer for H₂ production. An electrolyzer requires DC input and normally has a separate power converter that draws power from the electrical grid. By eliminating one set of power electronics, the cost of H₂ production could be significantly reduced. Therefore, grant applications are sought to design, fabricate, and test a wind-hydrogen electrolyzer system, focusing on the development of an integrated power electronics package that simultaneously converts a wind turbine’s output into grid quality power and controls hydrogen generation at the 100 kW to 1 MW scale. The challenge of this approach is to develop a device that can provide load control for the wind turbine while simultaneously producing DC for an electrolyzer and AC for the grid. No existing device can currently provide all three functions, and its design will require a thorough understanding of wind turbine and electrolyzer operations, as well as the requirements for grid connection including adherence to IEEE 519 grid interconnection standards. To be successful, such a device must be able to perform the described functions without adding more than 10% to the cost of a normal wind turbine power converter, for which current costs are approximately $70/kW. Grant applications should include projections for capital and operating costs and should clearly show how the research effort will proceed to hardware development, fabrication, and testing of a prototype wnd-H₂ power converter in Phase II, with demonstration in Phase III.

d. Improved Illumination—Numerous applications for efficient, power electronics exist today in lighting applications. The most pervasive opportunity is the application of power electronics to ordinary linear fluorescent lamp (LFL) ballasts, especially ballasts with dimming capability. Grant applications are sought to reduce the complexity and component count of ordinary LFL ballasts, while simultaneously conserving electricity and providing new functionality (such as integrated controls for networking, dimming, or diagnostics) at little or no additional costs. Advanced ballast features of interest include programmed controlled start, lumen-driven current controls to minimize output variations near the end of lamp life, continuous power factor correction, and automatic adaptation to differing lamp types and currents. These features may all be possible with new, novel ballast designs that also could increase lamp life, installation value, and most importantly, system efficacy.

In addition to fluorescent lamps, improved power electronics offer opportunities for other types of high power discharge lamps. For example, advanced power electronics may enable the use of low-power, high-intensity-discharge (HID) lamps that may be more energy efficient, have longer life cycles, and be more cost-competitive than the conventional lamps they may replace. Most significantly, the magnetic ballasts of conventional lamps possess limited functionality: while these ballasts may be adequate for many of today’s industrial applications, they fail to provide the flexible service demanded by other markets, such as retail and residential. Therefore, grant applications are sought to integrate advanced power electronics into these high intensity lighting systems to provide new service features such as programmed controlled start, dimming (even within a limited range), networking, lumen maintenance, and diagnostic interfaces. Of particular interest are approaches that also reduce the cost differential between fixed-output ballasts and dimming ballasts.

Finally, innovations in power electronics and controls could have application for solid state lighting (SSL). Existing power supplies for SSL are derived from commercial, off-the-shelf (COTS) supplies that are not optimized for the SSL devices, applications, or controls. Grant applications are sought to apply power electronics technology to efficiently power and control SSL, such that the range of performance is extended beyond, and yet costs remain competitive to, the COTS options.

References:

1. Aglan, O., Losses and Thermal Analysis of a High-Speed PM Generator for Microturbines, October 2003. (Available at: http://eme.ekc.kth.se/eme/publications/pdf/2003/aglen_loss_ieee2003.pdf)

2. Mekhiche, M., et al., High Speed Motor Drives for Industrial Applications, SatCon Technology Corporation, Cambridge, MA (Available at: http://www.satcon.com/pdf/hsmtia.pdf )

3. Ben-Yaakov, S. and Gulko, M., “Design and Performance of an Electronic Ballast for High Pressure Sodium (HPS) lamps,” IEEE Transactions on Industrial Electronics, 44(4):486-491, 1997. (ISSN: 0018-9456)

4. Ben-Yaakov, S., “Modeling the High Frequency Behavior of a Fluorescent Lamp: A Comment on ‘A PSPICE Circuit Model...’by T.-F.Wu, et al.,” IEEE Transactions on Industrial Electronics, 45(6):947-950, 1998. (ISSN: 0018-9456)

5. Ben-Yaakov, S., et al., “Statics and Dynamics of Fluorescent Lamps Operating at High Frequency: Modeling and Simulation,” IEEE Transactions on Industry Applications, 38(6):1486-1492, 2002. (ISSN: 0093-9994)

6. Schwarz-Kiene, P. and Heering, W, “Electronic Ballast for Pulsed Operation of Dielectric Barrier Discharges,” Proceedings of 8th International Symposium on the Science and Technology of Light Sources (LS-8), Greifswald, Germany, Aug. 30-Sept. 3, 1998, pp. 278-9, Institute for Low Temperature Plasma Physics, 1998. p.278-9 of viii+416 pp., 1998. (ISBN: 3-00-003105-7)

7. Advances in Switched-Mode Power Conversion, a collection of papers published by Caltech Power Electronics Group, 1983. (For ordering information, see: http://www.teslaco.com/books.htm) (For titles of papers, see: http://www.smpstech.com/books/bookm.htm )

8. Agarwal, A. K., et al., “SiC Power Devices,” Naval Research Reviews, 51(1):14-21, 1999. (ISSN: 0028-145X)

9. Shenai, K., et al., “Optimum Semiconductors for High Power Electronics,” IEEE Transactions on Electron Devices, 36(9):1811-1823, September 1989. (ISSN: 0018-9383)

10. Ozpineci, B., et al., “Effects of Silicon Carbide (SiC) Power Devices on PWM Inverter Losses,” The 27th Annual Conference of the IEEE Industrial Electronics Society (IECON'01), Denver, CO, Nov. 29-Dec. 2, 2002, pp. 1187-1192. (ISBN: 0-7803-7108-9)

11. Ozpineci, B., et al., “Testing, Characterization, and Modeling of SiC Diodes for Transportation Applications,” 33rd Annual IEEE Power Electronics Specialists Conference (PESC'02), Cairns, Australia, July 23-27, 2002, pp. 1673-1678, 2002.

12. Ozpineci, B., et al., “System Impact of Silicon Carbide Power Devices,” International Journal of High Speed Electronics and Systems, 12(2):439-448, 2002. (ISSN: 0129-1564)

13. Tolbert, Leon and Ozpineci, B., et al., “Impact of SiC Power Electronic Devices for Hybrid Electric Vehicles”... (Full text available at: http://www.ornl.gov/~webworks/cppr/y2001/pres/113883.pdf)

14. Trivedi, M. and Shenai, K., “High Temperature Capability of Devices on Si and Wide Bandgap Materials,” Transactions of the 33^rd Annual Meeting of the IEEE Industry Applications Society, St. Louis, MO, October 12-15,1998, pp. 959-962, 1998. (ISSN 0093-9994)

15. B. Ozpineci, L. M. Tolbert, S. K. Islam, “Comparison of Wide Bandgap Semiconductors for Power Electronics Applications,”10th European Conference on Power Electronics and Applications - EPE 2003, Toulouse, France, September 2-4, 2003. (Full text available at: http://www.ornl.gov/~webworks/cppr/y2001/rpt/118817.pdf)

16. Summary Report on the Systems Driven Approach for Inverter Research and Development Workshop, Baltimore, MD, June 2003, Technical Report, Albuquerque, NM: Sand National Laboratories, 2003. (Full text available at: http://www.eere.energy.gov/solar/sda_04_03.html)

17. Bower, W., “The AC PV Building Block Ultimate Plug-N-Play That Brings Photovoltaics Directly to the Customer,” Proceedings of the National Center for

Return to the Complete List of Topics.