Energy Storage Systems for EVs with Two Propulsion Machines

Three different energy storage system (ESS) topologies; battery-only, battery/ultra-capacitor (UC) and battery/UC/fuel-cell (FC) are studied for the electric vehicles (EVs) with two complementary propulsion machines. Convex optimization are utilized to optimize the power-split in hybrid energy storage system (HESS) so that the battery lifetime can be extended and the all-electric-range (AER) can be improved. The UC and FC can improve the performance of electric vehicles with two propulsion machines. The three systems are designed to have the same weights, and they are compared in terms of battery lifetime and the AER using simulation. According to simulation results, the longest AER is obtained via battery/UC/FC topology, and the best battery lifetime is achieved using the battery/UC topology.