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Electronic Combination of Energy Sources, 03-9087

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Principal Investigators
Joe Steiber
Craig M. Wall
Jack J. Harris

Inclusive Dates: 07/01/98 - Current

Background - Ultracapacitors and flywheels have been identified as sources or storage devices for auxiliary power in commercial, electric and hybrid, and military (air and ground) vehicles such as the More Electric Aircraft, the Future Scout, and the Future Combat Vehicles. While batteries are high-specific energy storage and low-specific power systems, ultracapacitors and flywheels are high-specific power and low-specific energy systems. Conceptually, an ideal system possessing high specific energy and power capacity, could be obtained by combining the disparate energy sources of batteries and ultracapacitors. However, dissimilar properties reflected in voltage-level mismatch create an enormous challenge of electrically connecting the two forms of energy sources. This search for a high-specific energy and power storage system cannot be ignored since the passenger and combat vehicles of the next century will, eventually, be equipped with these devices. The electronic power conversion community, however, still lacks a technique that efficiently combines energy systems of different types and promises both high power and energy capabilities as required in these applications. Hence, the development of an electronic technique to combine various forms of energy sources would provide the capability to develop the next-generation energy sources.

Approach - The Institute has devised a technique that uses an electronic circuit for efficient combination of energy sources. A novel bidirectional DC/DC power converter (patents pending) is being investigated for prototype development to regulate and control power flow in both directions (input to output and output to input). Additionally, regulation of the output voltage provides a feature not available in passive energy sources such as chemical batteries. The anticipated benefits of this power-electronic energy-conversion solution, called the Electronic Combination of Energy Sources (ECES), include low production cost; enhanced performance and output voltage regulation; increased regenerative braking energy capture; and reduction in conversion losses, resulting in increased operational efficiency. Additional benefits include extended battery life, increased energy storage system life cycles, reduced thermal problems with batteries; and integration of the ECES concept into SwRI and external hybrid/electric vehicle developmental projects.

Accomplishments - PSPICE computer models of the analog and digital elements constituting the ECES hardware have been developed and simulated, providing preliminary validation of the concept. In addition, a simplified version of the circuitry as well as a full-size printed circuit board were designed and fabricated. Preliminary testing of the simplified hardware validated the computer model predictions and demonstrated two of the five possible modes of operation. Test results have shown that the bidirectional power converter can indeed operate two independent energy sources with mismatched voltage levels by using state-of-the-art, high-power, fast-acting switching (up to 20 kilohertz) and an innovative topology.

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The SwRI-developed electronic energy coupling system provides an innovative method of regulating and controlling power flow in both directions

Electronic Systems and Instrumentation Program
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