Vol. 16, No. 1, February 2019


Filip Filipović, Bojan Banković, Milutin Petronijević, Nebojša Mitrović, Vojkan Kostić
Benchmarking of Phase Lock Loop Based Synchronization Algorithms for Grid-Tied Inverter
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Abstract: In renewable energy-based generation sources a phase locked loop is one of the most popular synchronization techniques. A rapid and precise grid voltage phase and frequency estimation under a wide spectrum of possible grid disturbances is its main objective. This paper compares popular grid synchronization algorithms on grid voltage anomalies. The compared algorithms are divided in three groups: without filtering, with filtering in synchronous reference frame and with filtering in stationary reference frame. The behaviour of the algorithms is tested in a laboratory, using dSpace 1103 as a platform on which the algorithms are compiled and OMICRON CMC 356 as a program¬mable grid voltage generator. The benchmarks conducted in this paper include voltage sags, grid voltages harmonics, DC offset and frequency step change. The obtained results show that there are significant differences in tested PLL responses for some networks disturbances.
Keywords: Benchmarking, Grid synchronization, Phase locked loop, Grid disturbance.

Nenad Petrović
Model-based Approach for Semantic-driven Deployment of Containerized Applications to Support Future Internet Services and Architectures
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Abstract: Due to increasing number of connected Internet of Things (IoT) devices, enormous amount of data needs to be transmitted to the Cloud for processing, while the network is becoming Cloud computing’s bottleneck. On the other side, the privacy and security issues in more sensitive application domains could dramatically restrict the freedom of data movement, so it is not possible to offload all the data to the Cloud for processing. Furthermore, the manual operations related to tuning and deployment of these applications are time-consuming and require additional effort. In this paper, a model-based framework for automated, semantic-driven (re-)deployment of containerized applications is presented, leveraging the synergy of Virtual Network Functions (VNFs) and SDN, tackling the mentioned issues.
Keywords: Container-based virtualization, DevOps, Docker, Edge computing, Future Internet, IoT, Model-driven engineering, NFV, Ontology, SDN, Semantic technology, VNF.

Miloš Milošević, Nenad Četić, Jelena Kovačević, Tihomir Anđelić
Lighting Control Using Raspberry Pi and Oblo Living Home Automation System
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Abstract: Home automation systems are bringing comfort and safety into the life of a modern human. They are becoming more popular each day and most of the well-known software companies are fighting to offer their newest solution in this area. OBLO Living is a home automation system developed by the scientific-research institute “RT-RK”. This paper presents one successful binding of the Raspberry Pi computer and the OBLO living system. The binding was made using a C++ application developed by the authors of this paper. The developed application is executed in real time on the Raspberry Pi platform. It supports a graphical user interface and its purpose is maintaining constant illumination of the room regardless of the daylight.
Keywords: Home Automation, Lighting Control, Oblo Living, Raspberry Pi.

Olivera Tomašević, Luka Mejić, Darko Stanišić, Vojin Ilić, Filip Gašparić
A Portable Device for Physiological Measurements in Biomedical Engineering Education
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Abstract: The physiological data acquisition system described in this paper is developed for the purposes of student laboratory exercises in biomedical engineering program. The system has the functionality of electrocardiography and electromyography monitoring and can be used as a photoplethysmograph. Alongside the portability, other significant capabilities of the system are concerned with the resources that allow the system's complete functionality without the cable connections to other devices. Besides, the system's open architecture enables various types of expanding and modifications, which is suitable for student project realizations.
Keywords: Acquisition, Electrocardiography, Electromyography, Electrophysi¬ology, Photoplethysmography.

Valentin Fedosov, Andrey Legin
Wireless Data Transmission in Underwater Hydroacoustic Environment Based on MIMO-OFDM System and Application Adaptive Algorithm at the Receiver Side
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Abstract: To increase the transmission speed in wireless data transmission systems, it is necessary to change either the bandwidth or the spectral efficiency, or both simultaneously. Systems based on Multi-Input Multi-Output (MIMO) methods can significantly increase spectral efficiency through parallel transmission using several transmitters and receivers. Such systems are particularly attractive for use in underwater acoustic communications systems, which are normally bandwidth-reduced. MIMO system along with OFDM (Orthogonal Frequency-Division Multiplexing) is a popular technology used in wireless networks to provide a high data transfer rate and resistance to multipath and fading of the channel. The implementation of such a system requires being aware of the channel condition at the receiver, and can be provided by means of using channel parameter estimation schemes. The adaptation task on the receiving side, apart from peak of pattern formation in the direction of the signal expected, also includes the interference-source suppression, that is, the issue of implementing spatial filtering of interference from other directions. However, since the signal and noise direction of arrival are unknown, we get a system with adaptive antenna array (AA). In the proposed research, a phase antenna array was used with controlled weighing.
Keywords: Antenna array (AA), MIMO, OFDM, Multipath, Adaptive algorithm, Hydroacoustic channel.

Marko Popović, Branislav Kordić, Miroslav Popović, Ilija Bašičević
Online Algorithms for Scheduling Transactions on Python Software Transactional Memory
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Abstract: Designing online transaction scheduling algorithms is challenging because one needs to reconcile three opposing requirements: (i) they should be fast, (ii) they should minimize makespan and maximize throughput, and (iii) they should produce conflict-free transaction schedules. In this paper we present four online transaction scheduling algorithms, namely, RR, ETLB, AC, and AAC algorithm, we prove their correctness and time bounds, and we conduct a theoretical analysis of the transaction schedules they produce, using three different workloads (RDW, CFW, and WDW). Finally, we compare various features of the four algorithms. The results are as expected, as we go from RR, over ETLB and AC, to AAC algorithms, the quality of the resulting schedules increases at the cost of increase of algorithm’s time complexity.
Keywords: Parallel programming, Transactional memory, Transaction scheduling, Algorithms, Time complexity.

Anandh Nagarajan, Sekaran Julius Fusic
Analysis and Design of LCS Resonant Cell Based Enhanced Zero-Voltage Transition DC-DC Boosting Converter
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Abstract: An enhanced zero-voltage transition boosting converter (EZVTBC) is introduced here which belongs to higher-order family. It exhibits lower source current and load voltage ripples and also it maintains better voltage gain with respect to traditional step-up converter. The zero-voltage transition is attained with an aid of a LCS resonant cell integrating Lr  Cr resonance tank network along with an extra switch. LCS resonant cell is the modified version of conventional ZVT switch cell and the salient feature of this cell is to eliminate peak current stress and conduction losses of main switch as this remains a predominant problem in hard-switched boost converter and it also improves efficiency. Initially, time domain expressions of EZVTBC are derived using Kirchhoff’s laws for different operational stages to predict the resonant transition phenomenon. The simulation is progressed in PSIM software in order to verify its soft-switching performance on a 12 – 24 V, 30 W converter and also dynamic performance of the converter has been studied with line and load variations. It is found that for rated load conditions, efficiency of the soft-switched converter is improved 5 to 10% approximately and resulted in 97%. Moreover the peak current stress and conduction losses were eliminated.
Keywords: Enhanced ZVT Boosting Converter, LCS resonant cell, Soft-Switching, Zero-Voltage Transition, Peak Current Stress.

Andrey Richter, Vladimir Y. Ignatiev, Maretta Kazaryan, Viacheslav Voronin, Mihail Shakhramanyan
Method of Constructing a Space-Time Grid of Variable Size Images and its Application in Image Processing of Landfills
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Abstract: The paper proposes a method of slicing space images into areas of varying sizes to automate the image processing, beginning from the receipt of raw data (download pictures) up to mapping of the underlying surface indices. Indices calculation are based on one image (the surface and the vegetation indices temperature, indices of objects detection on the ground and etc.) and their time series (conducting temporal processing). The downloading of the sources of satellite images algorithm from the sites archives of geodata from the initial data download (the observation area, stage, time period, etc.) is also represented. The procedure of cutting images into segments of varying sizes is described. It allows to use the “contents” of image both in general and for each pixel of the earth's surface to have a whole time series of the spectral brightness coefficients. Examples of time series of geo-referenced source images and the individual indices of the underlying surface are automatically generated by the algorithm method, for specific problems of space debris monitoring (vegetation indices reaction, the degree of soil degradation, detection of indices).
Keywords: Satellite imagery, Image slicing, Sites, Automation, Time series, Temporal processing, Detection, Index of the underlying surface, Landfills, Dumps, Waste disposal facilities.

©2019 Serbian Journal of Electrical Engineering