Hybrid Energy Storage System (HESS) in vehicular applications: A review on interfacing battery and ultra-capacitor units

One of the key components of every Electric Vehicle (EV)/Hybrid Electric Vehicle (HEV) is the Energy Storage System (ESS). The most widely-used ESS in electric drivetrains is based on batteries. As the specific power of batteries is normally low, they are hybridized with high-specific power storage elements such as ultra-capacitors in a Hybrid Energy Storage System (HESS) to meet harsh power requirements of the vehicle during acceleration and regenerative braking. This paper provides a thorough literature review on various configurations for interfacing battery and ultra-capacitor units to the DC bus forming a HESS in EV/HEV applications. It also reviews the energy management mechanisms used to split the power demand between battery and ultra-capacitor units.