Selection and design of ultra-capacitor modules for power conversion applications: From theory to practice

Electrochemical double layer capacitors (EDLC), well known as ultra-capacitors have been used intensively in power conversion applications such as controlled electric drives, active filters, power conditioners and uninterruptible power supplies. In such applications, an ultra-capacitor is used as a short-term energy storage device that can be fully charged/discharge within few seconds. This paper gives a comprehensive procedure and guideline for selection and design of ultra-capacitor module. Selection of main parameters, such as voltage and capacitance rating, is discussed in details. Conversion losses and efficiency as well as thermal design of the ultra-capacitor module are also discussed. In last part of the paper, design of voltage balancing circuit is addressed. At the end of the paper, a design example is given and the experimental results presented.