Monitoring the condition of electrolytic capacitors in practical applications is a topic that has been and remains the subject of much research. This article is part of research in this area. It develops a parameter observer (PO) and proposes its use for the determination of the equivalent capacity and equivalent serial resistance of electrolytic capacitors. The observer is an integral-open-loop type second-order system, the input of which is the voltage at the capacitor terminals measured during a two-stage capacitor’s discharging process through a variable resistor. The PO estimates the so-called time constant of the discharging circuit for each of the two stages from which values the capacitor’s parameters are calculated. The use of PO is illustrated for determining the output capacitor parameters of a buck DC–DC converter. The experiments were performed with two electrolytic capacitors with the nominal values 100 μF and 470 μF. Compared with other monitoring methods that use observers, the proposed observer is faster in tracking error mitigation, e.g., 10⁻³ s in comparison with 5·10⁻³ s or more. The low computational volume of the discrete-time PO allows the prospect of implementation in real time.

This paper describes the implementation of a parameter observer (PO) intended to estimate the capacitance and equivalent serial resistance of a capacitor (ESR). The implemented observer consists of a dynamic second-order discrete-time system. The input signal of the observer is the voltage at the terminals of the capacitor measured during its discharge across a variable resistance in two steps. The implemented observer can be used in quasi-online or offline mode. The theoretical and experimental supporting materials provide a comprehensive picture of the implementation and conditions of use of the PO. The experimental verification was carried out with a microcontroller with Cortex^®-M7 core architecture. The sampling time of the PO was 20 μs, and the estimation of the parameters was obtained before the end of the discharge of the capacitor. In the cases described in the paper, this means approximately 25 ms. Due to the PO’s capabilities (estimation speed, reduced computational complexity and precision)—proved by the experiments carried out on three electrolytic capacitors of 100 μF, 220 μF and 440 μF—the implementation is of interest for several applications, primarily in the field of power electronic applications.

The article focuses on devising solutions for monitoring the condition of the filter capacitors of DC-DC converters. The article introduces two novel DC-DC buck converter designs that monitor the equivalent series resistance (ESR) and the capacitance of capacitors using a parameter observer (PO) and simple variable electrical networks (VEN). For the first scheme, the PO processes in real time the voltage at the capacitor terminals during a discharge-charge cycle. For the second scheme, the filtering is performed with two or more capacitors in parallel, and the PO processes the voltage at the terminals of each capacitor during two discharge processes without interrupting the filtering operation of the converter. The paper presents the principles and theoretical support on which the two schemes of DC-DC buck converters are based, design details regarding PO and VEN, as well as experiments performed with each of the schemes. In the experimental schemes, the PO is implemented with a microcontroller, and the parameters of some aluminum electrolytic filter capacitors are calculated in a real-time manner of about $40 \mathrm{m}\mathrm{s}$. The calculation accuracy of the equivalent capacity is very good. Regarding the calculation accuracy of the ESR, it is shown that it depends on the fulfillment of certain ratios between the VEN resistances, on the one hand, as well as between them and the ESR, on the other hand.

Since 1992 (G. W. Hart [5]) the researchers started to take interest (focus) in developing a link between energetic signatures and household devices. In the ideal case, the main objective of the signature is to uniquely identify a device. One important characteristic of the signature is to be as compact as possible. In the present context, this paper proposes to use analytic expressions in form of transcendent function as signature for devices from the same consumption category: laptop, LCD-TV, washing machine, air conditioner. The paper presents a method to determine a signature based on the tangent function and genetic algorithm. Two case studies are shown. They will prove that it is possible to obtain an individual signature for household devices, and separate them from a common consumption.

Load current signatures are commonly used to characterize household electricity consumers. This paper introduces a new load signature class, the ellipse class, in addition to the tangent class already used in [10]. For both classes the signature consists of the set of parameters assigned to the two types of analytical functions. Signature determination is based on the operation of samples obtained at a very low frequency of approximately 20 Hz. This paper illustrates applications to both a single consumer and two consumers of the same class or of different classes.