Modelling of Ultracapacitor and Power Management strategy for the Parallel operation of Ultracapacitor and Battery in Electric Vehicle Configuration

The development of Electric Vehicles is gaining momentum due to diminishing fuel resources and environmental concerns. In Electric Vehicle, batteries form the primary energy storage. Sometimes available power from battery may not be sufficient to meet peak load demands. So, a secondary storage like ultracapacitor can be used in parallel with battery source to meet the power demand, where in the high frequency current requirements are met by ultracapacitor. The regeneration current transients can be taken by ultracapacitor, preventing battery recharge with high current transients. During regeneration, charging of battery with high current, affects battery life. The control logic can be formulated to meet these conditions, thus maintaining battery conditions optimum, thereby, reducing battery size and increasing the vehicle performance. Since, battery can be operated within safe limits battery life can be enhanced. This paper discusses Power Management strategy implementation for parallel operation of Ultracapacitor and Battery in EV Configuration. In this scheme, Ultracapacitor is connected to DC bus using bidirectional DC DC converter in CCM. Battery system is connected to bus using another bidirectional converter in VCM. Power Split Mechanism is implemented such that, drive current requirement, is met by the ultracapacitor depending on its voltage condition and remaining current requirement is met by battery. Thus the entire drive cycle requirement can be suitably achieved by using ultracapacitor in parallel with battery.