Design and analysis of a current-mode controlled battery/ultracapacitor hybrid

Abstract

This paper presents the design and analysis of a current-mode controlled battery/ultracapacitor hybrid operated with a pulsed power load. The system Ragone-type plot is constructed based on the steady-state analysis for power and efficiency design and optimization. The closed-loop control system is derived from a small-signal analysis for a compensator design to improve the steady-state accuracy and transient characteristics. The designed system allows the battery to be operated at a low-level constant current for a better cycle life, while the ultracapacitor, paralleled with the load, "free-wheels" a large current to enhance the power. The compensator is a simple proportional controller that can eliminate potential instabilities resulted from the high resistance mode of the battery.