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.

The article is part of the approach of finding the signatures for the individual household consumers using the voltage-current trajectories. Four classes of signatures are presented, known as: discontinuous tangent, tangent, ellipse, and hybrid. The functions describing the signatures are defined using a method based on non-linear regression and genetic algorithms. The method is implemented, with concrete results, on consumers from each of the four classes, starting with pairs of voltage-current values measured at low frequency, of approximately 20 Hz. This represents an important aspect from a practical point of view. There are four examples of signatures determined for: a laptop, a vacuum cleaner, a TV, and a fridge.

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The current study proposes a novel network control structure based on local and remote placed control elements, together with a nonlinear network transmission model recently proposed by the authors. For rejecting the disturbance effect of the network, a switched PD compensator is proposed. The control design methodology encompasses both analytical and numerical methods, so that both the stabilization and the tracking control objectives are met. The stability is assessed by considering the overall system as a switched linear system. Finally, the results are validated on a numerical example.

The Delayed Message Authentication Protocol (DeMA protocol) is a protocol that can be used in order to exchange authentic information between two entities by using a one-way chain (i.e. an array of elements generated by a one-way function) on each entity's side. The use of the discrete power function in the DeMA protocol offers the advantage that the length of the chains does not influence the computational time. In this paper we are concerned with the particular case of the discrete squaring function which offers more computational advantages since the elements of the one-way chains may be efficiently computed in a time-memory trade. The complete description of the DeMA protocol in the case of the discrete squaring function is given and also some experimental results are presented which help on understanding the computational performance of the protocol. By using this implementation of the DeMA protocol message authentication can be assured at the cost of almost one modular multiplication for each exchanged message.