Volume 70 (2019): Issue 5 (September 2019)

A new concept of switches selection in the meta-heuristic optimization process of optimal distribution network reconfiguration has been proposed. Based on the adaptive set of selectable candidates, the proposed concept determines the switch status. This approach prevents the creation of unfeasible solutions (non-radial and unconnected configurations), and significantly reducing the number of searches and accelerating the optimization process. Unfeasible solutions, created by meta-heuristic optimization rules, can be corrected by means of the proposed adaptive loop concept. The correct parts of the unfeasible solution are retained, while only the defective parts are replaced by the adaptively formed loops from the currently available conditions that respect the correct switching operations. In this way, the basic characteristics of the optimization process have been retained to the greatest possible extent. Tests were performed on a two different size standard distribution networks.

The selective harmonic elimination (SHE) is a preferable modulation technique in medium and high power converters applications as it enables for using low switching frequency with high flexibility to eliminate specific harmonics. The digital implementation of the SHE is a challenging issue as it requires a very accurate generation of the switching pulses. The theoretical calculation of the switching angles cannot guarantee the same results when digitally implemented by digital controllers. The digitizing process with a relatively low sampling frequency due to the digital implementation introduces error for each applied switching angle. Consequently, the applied switching angles will not match the theoretical ones resulted in residual errors for the selected harmonics that should be eliminated. This paper presents a new approach to improve SHE accuracy by online prediction and implementing of the closest true angles to minimize the residual harmonics.

Creeping breakdown caused by metal particles on the silicone rubber/XLPE interface of prefabricated cable joints often happens. Study on the development process of such insulation defect-led partial discharge (PD) can serve as a basis for the assessment of its severity level. In this paper, metal particles are sandwiched on the rubber/XLPE interface of a 35 kV prefabricated cable joint to simulate a creeping defect.

This paper presents a design of typical multilayer on-chip inductor to determine the layout parameters of the desired inductance value of electromagnetic modeling. The inductance and quality factor of multilayer on-chip spiral inductors are determined by its layout parameters and technological parameters. These layout parameters must be optimized to obtain the maximum quality factor at the desired frequency of operation. An electromagnetic model with fewer assumptions than empirical equations and higher efficiency than full-field solvers would be welcome. So would facile comparisons of different inductor structures. This paper describes recent works on the electromagnetic modeling of on-chip inductor structures applied to the comparison of inductor geometries, including the traditional spiral inductor and a novel multilayer inductor. The electromagnetic modeling of the investigative model is presented. The modeling and simulation are implemented using the method of moments. To simulate the proposed algorithm, the EM Simulator software is used.

Many induction heating processes must be controlled in accordance with the prescribed time evolution of temperature of the heated body (bodies). This requires a correct setting of field currents (amplitudes and frequencies) in the heating inductors that can vary either continuously or by steps. The paper presents a novel model of induction annealing of cylindrical aluminum billets based on solution of nonstationary forward and inverse tasks. The methodology is described in detail and illustrated with a typical example. Some of the results were verified experimentally.

Nowadays, the technology advancements of signal processing, low-voltage low-power circuits and miniaturized circuits have enabled the design of compact, battery-powered, high performance solutions for a wide range of, particularly, biomedical applications. Novel sensors for human biomedical signals are creating new opportunities for low weight wearable devices which allow continuous monitoring together with freedom of movement of the users. This paper presents the design and implementation of a novel miniaturized low-power sensor in integrated circuit (IC) form suitable for wireless electromyogram (EMG) systems. Signal inputs (electrodes) are connected to this application-specific integrated circuit (ASIC). The ASIC consists of several consecutive parts. Signals from electrodes are fed to an instrumentation amplifier (INA) with fixed gain of 50 and filtered by two filters (a low-pass and high-pass filter), which remove useless signals and noise with frequencies below 20 Hz and above 500 Hz. Then signal is amplified by a variable gain amplifier. The INA together with the reconfigurable amplifier provide overall gain of 50, 200, 500 or 1250. The amplified signal is then converted to pulse density modulated (PDM) signal using a 12-bit delta-sigma modulator. The ASIC is fabricated in TSMC0.18 mixed-signal CMOS technology.

A four-way network with 45 deg output phase shifts for feeding antenna array is studied in this work. To widen the phase imbalance, quarter wavelength short stubs with suitable characteristic impedances are introduced and numerically analyzed. Meanwhile, the wideband magnitude imbalance is also discussed by extending the inter-stage transmission line with proper electric length. The study is further confirmed by developing a prototype feeding network centered at 3 GHz. Results from the fabricated prototype network exhibit wideband good performance, both from numerical evaluations and experimental demonstrations.

In this study, a simple, adjustable, bidirectional tilt sensor was designed using a pair of linear Hall effect sensors and magnets. Theoretical analysis and experimental results of the sensor system were presented. The working principle of the designed sensor is based on sensing the magnetic field of a mobile magnet which displaces with respect to the tilt angle. Two magnet sets were placed at the two ends of the system to apply repulsive restoring forces on the mobile magnet. The mobile magnet was coated with a light hydrocarbon based ferrofluid as a lubricant to reduce friction. Fixed Hall effect sensors were placed face to face at the two sides of the mobile magnet to monitor the magnetic field of the mobile magnet. It was shown that both experimentally and theoretically, it is possible to measure the approximate tilt angle linearly and quadratically by calculating the sum and difference of the Hall sensor voltages for the relatively small movements of the mobile magnet. Moreover, the system was also examined for the different sets of side magnets. For three different side magnet configurations, approximately 0.7, 1.1 and 1.68 V/rad sensitivity values were observed in the linear range.

This paper proposes a design of a stabilization control for one-sided Lipschitz (OSL) nonlinear systems in new reciprocal state space (RSS) framework. The main objective is to extend the state derivative feedback stabilization methods for a class of nonlinear systems where the nonlinearity of derivatives state satisfies the OSL properties in RSS. The presented controller is composed of a state derivative feedback approach in order to ensure asymptotic stability in the sense of Lyapunov. The first approach deals with the synthesis of a basic controller by adopting a simple transformation of Linear Matrix Inequality (LMI) to standard algebraic Ricatti equation (ARE). The second is an extension to adaptive version with adjustment parameters. High performances are shown through real-time implementation with a hardware in the loop (HIL) mode using digital signal processing (DSP) device (DSpace DS 1104).

This article is focused on the analysis of impacts on the cross-border transmissions between Slovakia and Hungary and between Slovakia and Ukraine after the completion of the new 400 kV transmission lines on the cross-border profile Slovakia – Hungary. A simulation model of the Slovak transmission system in software ETAP was created, which is set for exploring the impacts of the new Slovak – Hungarian transmission lines 447, 480 and 481 on the cross-border and national transmissions. Correctness of the created simulation model was confirmed by the match of the measured values from winter nationwide measurement with the calculated values from the simulation model. Subsequently, several variants of the Slovak transmission system operation before and after completion of the new power lines to Hungary were evaluated.