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 - 09/30/00

Background - Conceptually, an ideal energy storage for hybrid and electric vehicles is one with high specific energy and high power capacity. Rather than developing one "super battery," the same result could be obtained by combining these disparate energy sources (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 because the passenger and combat vehicles of the new century will, eventually, be equipped with these devices. The electronic power conversion community, however, still lacks a technique that efficiently combines different types of energy systems and that promises the high-power, high-energy capabilities required by 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 an electronic circuit for efficiently combining 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. In addition to being integrated into SwRI's and other external hybrid/electric vehicle developmental projects, the anticipated benefits of this power-electronic energy conversion solution, called electronic combination of energy sources (ECES), include:

  • Low production cost

  • Enhanced performance, output voltage regulation

  • Substantially increased regenerative braking energy capture

  • Significant reduction in conversion losses, resulting in increased operation efficiency

  • Extended battery life

  • Increased energy storage system life cycles

  • Reduced thermal problems associated with batteries

Accomplishments - Mathematical computer models of the analog and digital elements constituting the ECES hardware were developed and simulated for selected conditions to validate the concept. In addition, a simplified version of the circuitry and a full-size printed circuit board were designed and fabricated using techniques not previously used at SwRI. Test results confirmed the results obtained through simulation. More importantly, test results confirmed that the innovative topology of the bidirectional power converter can operate two independent energy sources with mismatched voltage levels. State-of-the-art, high-power, fast-acting switching devices with operation exceeding 20 kHz were used. Additional analysis and testing are planned to further demonstrate the new system capabilities.

The Institute's full-size printed circuit board of the ECES is shown during testing.

Materials Research and Structural Mechanics Program
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