This thesis aimed to analyze the supercapacitor behavior to verify the possibility of the estimation of its internal parameters for diagnostic purposes. The target has been reached firstly by a theoretical analysis which showed that the crucial parameters for diagnostic purposes are the voltage of the non-linear capacitance, since it gives a measure of the stored charge, and the parasitic resistance which limits the maximum allowable current and influences losses. Secondly it has been verified when a supercapacitor parameters are observable and finally an extended Kalman filter to obtain such parameters has been set up. The Thesis demonstrated that a supercapacitor can be modelled by a 2-branch Double-Layer capacitor including a non-linear capacitance, it is observable thanks to the fact that such SC can be characterized by a parabola in the state space region in which the observability is not guaranteed. It has been shown that this curve usually does not cross the normal operating region corresponding to a part of the first quadrant of the state space plane. Then the internal parameters have been estimated by an Extended Kalman Filter , or EKF . A windowed-EKF , or wEKF , has been used for learning the EKF behavior, when it has to engage with measured the output y with respect to pre-configured time ranges. The main parameter to be estimated has been identified in the voltage of the non-linear capacitance since it gives a measure of the stored charge and of the parasitic resistance. The goal of diagnostics is reached since a very low error between the real and estimated values of the voltage on the non-linear capacitance has been obtained. The assessed method can be operated on-line: during the lifecycle of a SC , some values could differ from rated ones; so that, a possible SC degradation can be detected. In this case the SC replacement can be programmed with benefits for operators and equipment.
|Titolo:||Diagnostic of Supercapacitors based on State Estimation through Extended Kalman Filter|
|Citazione:||Rodono', G.Diagnostic of Supercapacitors based on State Estimation through Extended Kalman Filter.|
|Appare nelle tipologie:||4.2 Tesi di dottorato|