Development of Supercapacitor Technology and Its Potential Impact on New Power Converter Techniques for Renewable Energy

Abstract

To overcome short-term input energy fluctuations, and to offer complete 24-h energy solutions based on renewable resources such as solar and wind, energy storage devices are mandatory. A relatively new storage family is the supercapacitor (SC), which were developing rapidly over the last 15 years, and are yet to compete with rechargeable batteries. Today with three different commercially available SC families developing rapidly, with 1-70 000 F per single cell, at least one of them is reaching the specific energy of lead-acid batteries. All new families of SCs have charge/discharge life cycles of several orders larger than rechargeable battery chemistries, and their usage in energy storage systems is rapidly advancing. The SC-assisted converters are a new family of very low-speed converters, where a power electronic building block is combined with an SC bank to achieve high end-to-end efficiency, with the added advantage of dc-uninterruptible power supply (UPS) capability within the converter. This article provides an overview of the new SC-assisted loss management theory applied to SC-assisted converters, with practical examples of implementation useful in renewable energy systems such as SC-assisted low dropout regulator, SC-assisted LED, SC-assisted server rack power architecture, and SC-assisted wide-input inverter. In developing these new converters, useful in renewable energy systems, SCs are considered as a new device family with five to six-order larger capacitance for the same canister size, helping the achievement of the long time constant circuits.