Ultracapacitors as unique energy storage for a city-car using five-level converter

A lightweight citycar, using five-level inverter and only ultracapacitors as energy storage is presented. Ultracapacitors (UCAPS) allow very fast charge and the five-level inverter permits to balance the discharge of UCAPS and also to improve the current waveforms that feed the traction motor. To get better efficiency, a brushless dc (BLDC) motor and a special control strategy is used. The main objective of this project is to be ready for replacing actual UCAPS for future elements using nanotechnology, which will be able to increase specific energy at list twenty times compared with actual UCAPS, keeping their fast charging characteristics and long cycle life.