Robust control of an ultracapacitor-based hybrid energy storage system for electric vehicles

This paper presents a new robust control scheme for the efficiency optimization of an ultracapacitor-based hybrid energy storage system. The purpose is to improve the performance of the battery supply with the addition of an ultracapacitor as an auxiliary energy storage device for electric vehicles applications. The control scheme is based on an internal hysteresis-based current control loop combined with an external synergy-based control loop for dc bus voltage regulation. The improvement in performance is demonstrated through numerical simulation. The results show that efficient power balance is achieved between the two embedded storage units. The ultracapacitor is able to absorb the sudden load variations and achieve more efficient use of the batteries.