State of Charge Estimation for Ultracapacitors based on the Fractional Calculus

In recent times, ultracapacitors (UCs) have been extensively used energy storage device in various industrial applications. An enabling energy management system should portray the reliable and efficient operation of the system, in which monitoring of the state of charge is a crucial factor. In UC powered systems, accurate modeling and charging status prediction of UCs are vital for reliable as well as safe operation. In this paper, fractional calculus-based model is developed to emulate UCs dynamics based on series resistance, constant phase element (CPE) and Walburg element. Fractional observer technique is introduced to estimate State of charge (SOC) of UC from fractional order representation. The simulation result shows that the fractional order model with reasonable error provides an acceptable accuracy in SOC estimation.