Review of alternate energy storage systems for hybrid electric vehicles

Batteries, ultra capacitors, and fuel cells are widely being proposed for electric and plug-in hybrid electric vehicles (EVs/PHEVs) as an electric power source or an energy storage unit. Implementation of several control methods have been presented in the past, with the goal of improving battery life and overall vehicle efficiency. It is clear that the control objectives vary with respect to vehicle velocity, power demand, and state-of-charge of both the batteries and ultra-capacitors. Hence, an optimal control strategy design is the most critical aspect of an all-electric/plug-in hybrid electric vehicle operational characteristic. This paper initially discusses energy storage characteristics, and then describes types of hybrid electric vehicle energy storage systems (ESS), energy source models, and type of DC/DC converters.