Online state and parameter estimation of Battery-Double Layer Capacitor Hybrid Energy Storage System

Hybrid Energy Storage Systems (HESS) are gaining popularity due to their ability to compensate for the deficiencies of the conventional single energy storage solution. Battery-Double Layer Capacitor (DLC) is one of such HESS that is being adopted for different applications such as vehicle propulsion, auxiliary power unit and renewable energy storage. Real-time estimation of the states and parameters of such HESS is crucial for safe, efficient and optimal operation. In this paper, an online state-parameter estimation scheme is presented based on the electrical and thermal dynamics of the battery and DLC. The estimation scheme consists of two separate state-parameter estimators for battery and DLC each of which exploits a cascaded observer-based structure. The observers are designed based on sliding mode methodology. Theoretical verification of the overall state-parameter estimation is provided using Lyapunov´s argument. Effectiveness of the scheme is verified via simulation studies.