Observability of a 2-branch Double-Layer-Capacitor

Abstract

Abstract. The paper proposes a study of the observability of a 2-branch Double-Layer Capacitor (DLC) mathematical model, derived from its well known 2-branch nonlinear physical model. The study is a basis to perform the diagnosis of the system by employing observers. The analysis is carried out by means of the sufficient rank condition of the observability matrix for nonlinear models. It is shown that the rank condition is satisfied everywhere in the two-dimensional state space, except for a characteristic curve in the plane defined by the two state variables. This curve is usually outside the usual range of operation of Double-Layer Capacitors available on the market. Finally, it is shown that the above curve is sensitive to the resistance of the branch containing the nonlinear capacitance, i.e. the faster branch. In particular, increasing this resistance can cause the curve to intersect the region of usual range of operation of a DLC.Keywords. DLC, SC, supercapacitor, observability, state-space, diagnosis. List of variables Variables(s) DescriptionDim.