A new configuration for enhanced integration of a battery-ultracapacitor system

The principal shortcoming of the batteries in electric vehicles is their limited specific power. The potential solution is having a hybrid energy storage system (HESS) that integrates the ultracapacitor (high specific energy) with the battery (high specific energy), thus ensuring high specific energy and power. Classically, a bidirectional DC-DC converter integrates the two sources, but the converter introduces a delay during the charging-discharging transition of the ultracapacitor. This work proposes a novel converter topology that interfaces the two sources, eliminating an existing transition delay, providing a fault -tolerant operation in case of a switch failure, and efficiently charging the ultracapacitor. Additionally, an algorithm is presented that facilitates energy sharing between the battery and the ultracapacitor, preventing overloading of the battery and ensuring that the ultracapacitor contributes to the peak load demand. The proposed configuration and energy management algorithm are validated experimentally using a 24V laboratory prototype.