Interface converters for ultra-capacitor applications in power conversion systems

Electrochemical double layer capacitors (EDLC), well known as the ultra-capacitors have been used intensively in power conversion applications such as controlled electric drives, active filters, power conditioners and uninterruptible power supplies. The ultra-capacitor is employed as the energy storage device that can be fully charged/discharge within few seconds. To achieve better flexibility and efficiency of the entire conversion system, the ultra-capacitor is connected to the power conversion system via an interface dc-dc power converter. This paper gives an overview of ultra-capacitor applications with focus on the interface converter, topology selection, analysis and hardware as well as the controller design. As an example, three-level dc-dc converter with flying output is analyzed in details. A prototype of 5.5kW was designed and experimentally verified on a general purpose controlled electric drive.