Design and control of novel power electronics interface for battery-ultracapacitor Hybrid Energy Storage System

Hybrid Energy Storage System (HESS) is combination of two or more energy sources with complementary characteristics formed to provide solution to a particular energy problem. Battery together with Ultracapacitor makes an excellent HESS for electric vehicles. However, it requires proper interface electronics and its control to get the desired benefits like longer driving range, better acceleration performance, controlled regenerative braking, smaller battery pack and longer battery life. The work presented in this paper tries to minimize the stresses on battery, present during periods of acceleration and braking of PMDC traction motor by adding ultracapacitor in parallel as an auxiliary power source. Unidirectional and bidirectional DC-DC converters are used with battery and ultracapacitor respectively to ensure proper energy flow to (and from) motor during different stages of driving cycle. State space averaging technique is used to model the converters. The power management algorithm intelligently divides the current demanded by motor between battery and ultracapacitor current The control strategy uses classical controllers, which are designed using bode plot based technique. The simulation is done on MA TLAB/SIMULINK.