Adaptive control of an ultracapacitor energy storage system for hybrid electric vehicles

An Ultracapacitor-based Energy Storage System (UESS) as an alternative to batteries is becoming attractive for Hybrid Electric Vehicles. This energy storage concept requires innovative control methods. In this paper, an UESS composed of two ultracapacitor banks and a boost converter is studied. The control objective is to regulate the output voltage subject to unpredictable incoming and outgoing energy flows. A hybrid control strategy, namely Gain Scheduling with Fuzzy Logic Control, is proposed. It consists of an Linear Quadratic Regulator (LQR) and a Fuzzy Logic Controller (FLC). At each system operating point, properly-designed LQR can achieve fast damping for short-term or small disturbances on input and load currents. When system operating point changes, FLC can trace the changes and adaptively adjust the parameters for the LQR controller. The proposed control method is simulated for validity.