Development of a hybrid energy storage system (HESS) for electric and hybrid electric vehicles

Extensive use of internal combustion engine (ICE)-based vehicles has contributed to severe adverse impacts on the environment and accelerated depletion of fossil fuel reserves, leading to considerable rise in price of gas over the past two decades. These challenges, plus the low efficiency associated with the conventional drivetrains, have made the automotive industry seriously consider and move towards drivetrain electrification in vehicular systems. In electrified vehicles, the propulsion is fully or partially provided by electric motors, powered by onboard energy storage systems. In an attempt to make up for the limitations of the existing energy storage devices and contribute to vehicle electrification movement, this paper examines the feasibility and capability of a hybrid energy storage system (HESS), composed of battery and ultra-capacitor units, through simulation and experimentation using a laboratory prototype. The choice of HESS topology has been made based on simplicity of power and control circuits, cost and performance. The design takes into consideration the required power, the converter losses, limitations of energy storage devices, and quality of the current drawn from battery cells. Experimental results are provided to verify the analytical expectations and simulation results.