State-of-Charge Estimation of Supercapacitors: A Switched Systems Approach
Heng Li, Wei He, Xueying Fang, Shuo Li
Abstract
State-of-Charge (SOC) estimation of supercapacitors has been extensively studied in the literature, with most of the existing studies focusing on the SOC estimation of a single supercapacitor cell. However, in practical applications, supercapacitors are often connected to balancing circuits to eliminate cell imbalances. When the balancing circuit is activated, the system dynamics of the cell switches to a new mode, implying that existing SOC estimation methods cannot be applied directly. In this paper, we a switched systems approach to estimate the SOC of the cells. We model the switching system for the RC model of the supercapacitor with a switched resistor balancing circuit and carefully study the continuity of the state and the observability of the switched system. Then, we propose a switching observer and analyze its convergence property. We have also developed an experimental platform to verify the effectiveness of the proposed method and the performance of the different observers is compared. The design of the observer gain is explained in the discussion.