A novel hybrid energy storage system for electric vehicles

A novel Hybrid Energy Storage System (HESS) for Electric Vehicles (EVs) is proposed in this paper. It consists of a battery pack and an ultra-capacitor module (UC), which are suitably coupled through a Three-Level Neutral-Point Clamped Converter (NPC). Particularly, although the UC is integrated within the DC-link, its voltage can be varied within a wide range, thus assuring its full exploitation without the need of any DC-DC converter. This is achieved by means of an appropriate HESS control system, which also prevents the battery pack from handling sudden power fluctuations. The effectiveness of the proposed HESS is verified through a simulation study, which refers to an electric propulsion system based on a Surface-Mounted Permanent Magnet Synchronous Machine (SPM), which is supplied by the proposed HESS through the NPC.