Battery management for hybrid electric vehicles using supercapacitors as a supplementary energy storage system

Modeling and simulation of the energy storage system in conjunction with the converter system is a judicious and cost-effective method for extending and enhancing the increased life and increased operating range for hybrid and electric vehicles, golf carts, electric scooters, and wheelchairs. Similar optimization techniques are also of paramount significance for battery-powered backup systems such as UPS for computers and telecommunication systems. Considerable effort is put into the selection of the appropriate battery with specific regard to the battery´s State-of-Charge (SOC) and battery reserve time during the discharge profile for the various loading conditions. The addition of supercapacitors to the battery in the energy storage system both improves the energy delivery of the system and extends the life of the battery. During peak demands, the battery alone would have to deliver and receive the high peak currents. At low SOC, the battery has a higher internal resistance and would tend to overheat and not be able to handle the current peaks. Using supercapacitors, which have inherently low ESR, allows a realizable and efficient storage system for these high peak currents, and thus the performance of the energy storage system is enhanced, the efficiency and operating time improved, and the battery life extended.