Elektronika ir Elektrotechnika http://eejournal.ktu.lt/index.php/elt <div>ELEKTRONIKA IR ELEKTROTECHNIKA is&nbsp;a peer-reviewed bimonthly research journal of Kaunas University of Technology.</div> <p>The research journal ELEKTRONIKA IR ELEKTROTECHNIKA publishes previously unpublished manuscripts that will have a high impact in the field of electronics and electrical engineering. It targets not only certain field specialists, but the wider public also.</p> Kaunas University of Technology en-US Elektronika ir Elektrotechnika 1392-1215 <p>Copyright terms are indicated in the Republic of Lithuania Law on Copyright and Related Rights, Articles 4-37.</p> Title http://eejournal.ktu.lt/index.php/elt/article/view/24820 Elektronika ir Elektrotechnika Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 1 1 Editorial Board http://eejournal.ktu.lt/index.php/elt/article/view/24821 Elektronika ir Elektrotechnika Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 2 3 Environment Mapping Algorithm Using Semantic Description and Constrained Delaunay Triangulation http://eejournal.ktu.lt/index.php/elt/article/view/24818 <p>The article discusses the issue of creating an environment’s map with semantic division of areas. This simplifies some aspects of mobile robot control and permits the robot to carry out tasks issued in a human-understandable form. The article presents an innovative algorithm for mapping the environment by a mobile robot. Its novelty stems from the use of a semantic description of the world and Delaunay triangulation method with constraints. This description is used to segment the map of the environment and to reduce redundant information. The developed algorithm is based on the idea of extending the borders of the already discovered areas; they are expanded as the new data are collected from the environment. These data contain information about the location of semantic types in the explored space and is used to update the areas during analysis of the environment’s map. The beforementioned triangulation method is used in that process. The performance of the proposed algorithm is tested in simulation studies. The obtained results show a good computational efficiency of the method, which is crucial in the problem of environment exploration by mobile robots with limited computational resources.</p> Daniel Figurowski Pawel Dworak Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 4 7 10.5755/j01.eie.25.6.24818 MSSB to Prevent Cable Termination Faults for Long High Voltage Underground Cable Lines http://eejournal.ktu.lt/index.php/elt/article/view/24819 <p>Cable termination fault is one of the most important problems for high voltage underground cable lines (HVUCL). Harmonic current (HC) and the sheath current (SC) are causes of cable termination faults of HVUCL. The sheath voltage (SV) of cable increases due to SC and HC also. So, the electroshock risk for human occurs. In this study, cable termination faults are examined for long HVUCL that is connected to electric network with high harmonic distortion rate. In literature, solid bonding (SB) and sectional solid bonding (SSB) methods are used to reduce harmonic distortion rate and SC effect in HVUCL. However, when SB and SSB methods are used for bonding of long HVUCL, harmonic distortion limit and touch voltage limit are exceeded. Therefore, the modified SSB (MSSB) method is developed for bonding of long HVUCL. SV of HVUCL should be known to use MSSB for bonding of long HVUCL. Then SV of HVUCL is forecasted by using artificial neural network and hybrid artificial neural networks (HANN) before the long HVUCL is installed. MSSB parameters should be optimized, so that optimization methods are used for optimization of MSSB and HANN. When MSSB method is used for bonding of long HVUCL, harmonic distortion limit and touch voltage limit are not exceeded under high harmonic distortion conditions.</p> Bahadir Akbal Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 8 14 10.5755/j01.eie.25.6.24819 A Novel Hybrid Compensation Method Reducing the Effects of Distorted Input Voltages in Matrix Converters http://eejournal.ktu.lt/index.php/elt/article/view/24830 <p>Matrix converters have the most compact and efficient AC-AC converter structure due to the lack of the DC intermediate components. The matrix converter makes a single-stage conversion directly connecting any terminal of voltage source to any terminal of load. This outstanding feature leads to some problems that must be overcome under the distorted input voltage conditions. A matrix converter has low immunity to power source disturbances, because it has no DC intermediate circuit. Any disturbance in the power source creates a negative effect on the load of the matrix converter and on the current drawn from the source. In this study, a novel compensation method, which provides immunity against input voltage disturbances, is suggested for the matrix converter. The suggested method has a hybrid structure, which includes both feedforward and fuzzy logic controller based feedback methods. The effectiveness and accuracy of the suggested new hybrid compensation approach are proved by the various results obtained.</p> Hulusi Karaca Ramazan Akkaya Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 15 21 10.5755/j01.eie.25.6.24830 Electronically Isolated Measuring Circuit for Multicell Traction Battery Modules Identifying State of Charge (SOC) Values http://eejournal.ktu.lt/index.php/elt/article/view/24822 <p>Paper focuses on the topic related to State of Charge (SOC) estimation of the battery modules. The design issues of the electronic circuit suited for very accurate voltage and current measurement used for evaluation of the SOC parameters of battery module (NexSys 12&nbsp;V) are presented. The SOC evaluation is not described here, but the principles are based on the open-circuit voltage measurement in combination with the coulomb counting method. Both methods are considered within the practical design of the measuring circuit of traction lead-acid batteries connected in series (3 cells). The circuit proposal is verified by the simulation model and consequently by the experimental measurement. Mutual comparisons are done for each battery within the module. The results show a very high accuracy between the simulation and measurement, while the relative tolerance varies from - 7&nbsp;% to 1&nbsp;% within wide measuring ranges.</p> Michal Pipiska Michal Frivaldsky Matus Danko Jozef Sedo Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 22 27 10.5755/j01.eie.25.6.24822 Electronically Adjustable Emulator of the Fractional-Order Capacitor http://eejournal.ktu.lt/index.php/elt/article/view/24823 <p>This paper presents a design of the controllable emulator of the FOC (Fractional-Order Capacitor) and its application. The circuit is based on 5<sup>th</sup>-order RC topology (type Foster I), where the passive elements in the topology are replaced by electronically adjustable components. The proposed emulator is based on OTA (Operational Transconductance Amplifier) and VDCC (Voltage Differencing Current Conveyor). The electronically controllable resistors are implemented by OTAs. The electronically tunable capacitors are implemented using capacitance multipliers, which employ VDCCs. The proposed structure provides the electronic control of the order and electronic shifting of the frequency band of the approximation validity. The proposed FOC emulator is also used for fractional-order filter design. The proposed circuits are verified using PSpice simulations.</p> Jan Dvorak David Kubanek Norbert Herencsar Aslihan Kartci Panagiotis Bertsias Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 28 34 10.5755/j01.eie.25.6.24823 A Hardware Approach of a Low-Power IoT Communication Interface by NXP FlexIO Module http://eejournal.ktu.lt/index.php/elt/article/view/24824 <p>This article describes implementation possibilities of specialized microcontroller peripherals, as hardware solution for Internet of Things (IoT) low-power communication, interfaces. In this contribution, authors use the NXP FlexIO periphery. Meanwhile, RFC1662 is used as a reference communication standard. Implementation of RFC1662 is performed by software and hardware approaches. The total power consumption is measured during experiments. In the result section, authors evaluate a time-consumption trade-off between the software approach running in Central Processing Unit (CPU) and hardware implementation using NXP FlexIO periphery. The results confirm that the hardware-based approach is effective in terms of power consumption. This method is applicable in IoT embedded devices.</p> Libor Chrastecky Jaromir Konecny Martin Stankus Michal Prauzek Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 35 39 10.5755/j01.eie.25.6.24824 Performance Assessment of a High-Powered Boost Converter for Photovoltaic Residential Implementations http://eejournal.ktu.lt/index.php/elt/article/view/24825 <p>This paper introduces a new boost converter operating in several duty cycles with a high powered and no transformer design for Photovoltaic residential implementations. The proposed converter is performed without any extra power switch by a voltage pre-amplifier unit between the input inductor and the power switch and is derived with a simple structure. The designed converter provides a voltage gain by 38 times for the operation of 90% of the duty cycle. This condition shows that the proposed converter has more efficient compared to the conventional boost converters. Besides, a higher amount of DC gain is possible by adding a cascade blocks connection of switched-capacitor (SC) in the converter’s output. The operational principles are evaluated to justify the utility of converter for residential PV systems in the study. Also, a 200&nbsp;W powered prototype converter is implemented by applying a commercial PV panel in the laboratory. The experimental results confirm both the mathematical and simulation results.</p> Davood Ghaderi Gokay Bayrak Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 40 47 10.5755/j01.eie.25.6.24825 A New Heuristic Approach for Treating Missing Value: ABCimp http://eejournal.ktu.lt/index.php/elt/article/view/24826 <p>Missing values in datasets present an important problem for traditional and modern statistical methods. Many statistical methods have been developed to analyze the complete datasets. However, most of the real world datasets contain missing values. Therefore, in recent years, many methods have been developed to overcome the missing value problem. Heuristic methods have become popular in this field due to their superior performance in many other optimization problems. This paper introduces an Artificial Bee Colony algorithm based new approach for missing value imputation in the four real-world discrete datasets. At the proposed Artificial Bee Colony Imputation (ABC<sub>imp</sub>) method, Bayesian Optimization is integrated into the Artificial Bee Colony algorithm. The performance of the proposed technique is compared with other well-known six methods, which are Mean, Median, k Nearest Neighbor (k-NN), Multivariate Equation by Chained Equation (MICE), Singular Value Decomposition (SVD), and MissForest (MF). The classification error and root mean square error are used as the evaluation criteria of the imputation methods performance and the Naive Bayes algorithm is used as the classifier. The empirical results show that state-of-the-art ABC<sub>imp</sub> performs better than the other most popular imputation methods at the variable missing rates ranging from 3&nbsp;% to 15&nbsp;%.</p> Pinar Cihan Zeynep Banu Ozger Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 48 54 10.5755/j01.eie.25.6.24826 Research on Big Data Mining Technology of Electric Vehicle Charging Behaviour http://eejournal.ktu.lt/index.php/elt/article/view/24827 <p>Thousands of electric vehicles (EV), which are large in number and flexible in their use of electricity, will be connected to the power system in the near future, which will bring more uncertainty to the power system. Therefore, it is necessary to study the general characteristics of EV charging behaviours. In the charging process, big data regarding charging behaviour of EVs are generated. This paper proposes a big data mining technique based on Random Forest and Principle Component Analysis for EV charging behaviour to identify and analyse clusters with different charging characteristics from the big data. This paper uses Dundee’s January 2018 EV charging data to conduct experiments, and obtains the charging behaviour clusters of the workdays, weekends, and holidays of January. The superiority of the random forest algorithm in the EV clustering problem is reflected when compared to the Euclidean distance method. The clusters obtained by the random forest algorithm have clearer characteristics, including the user’s charging method and travel behaviour. The results show that the charging behaviour of EVs has certain regularity, and the charging load has obvious peak-to-valley difference that is necessary to be regulated.</p> Yujun Liu Yi Hong Cheng Hu Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 55 61 10.5755/j01.eie.25.6.24827 A Similarity-Inclusive Link Prediction Based Recommender System Approach http://eejournal.ktu.lt/index.php/elt/article/view/24828 <p>Despite being a challenging research field with many unresolved problems, recommender systems are getting more popular in recent years. These systems rely on the personal preferences of users on items given in the form of ratings and return the preferable items based on choices of like-minded users. In this study, a graph-based recommender system using link prediction techniques incorporating similarity metrics is proposed. A graph-based recommender system that has ratings of users on items can be represented as a bipartite graph, where vertices correspond to users and items and edges to ratings. Recommendation generation in a bipartite graph is a link prediction problem. In current literature, modified link prediction approaches are used to distinguish between fundamental relational dualities of like vs. dislike and similar vs. dissimilar. However, the similarity relationship between users/items is mostly disregarded in the complex domain. The proposed model utilizes user-user and item-item cosine similarity value with the relational dualities in order to improve coverage and hits rate of the system by carefully incorporating similarities. On the standard MovieLens Hetrec and MovieLens datasets, the proposed similarity-inclusive link prediction method performed empirically well compared to other methods operating in the complex domain. The experimental results show that the proposed recommender system can be a plausible alternative to overcome the deficiencies in recommender systems.</p> Zuhal Kurt Kemal Ozkan Alper Bilge Omer Nezih Gerek Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 62 69 10.5755/j01.eie.25.6.24828 A New Method in Pilot Reuse Factor Selection in Spectrum Efficient Massive MIMO Systems http://eejournal.ktu.lt/index.php/elt/article/view/24829 <p>Spectrum efficiency studies of Massive MIMO systems have continued and still have not been fully explored in the literature. Therefore, the spectrum efficiency definition of a particular user in a cell in a Massive MIMO network is expressed in this paper. In addition, the uplink spectrum efficiency expressions for the Rayleigh fading are included. The Monte Carlo simulations are performed to verify these expressions. Due to the expectation of reaching to a thousand antennas together with the millimetre wave structure in the next years, in this study, it is contributed to the literature by explaining how to select the pilot reuse factor. The realization of this contribution is based on Zero Forcing (ZF) and Maximum Ratio Combining (MRC) schemes. The results of this study are useful for optimal design conditions, such as the number of antennas on the base station and pilot reuse factor selection for the next generation networks in order to obtain spectrum efficiency in Massive MIMO systems.</p> Osman Dikmen Selman Kulac Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 70 77 10.5755/j01.eie.25.6.24829 Reviewers http://eejournal.ktu.lt/index.php/elt/article/view/24831 Elektronika ir Elektrotechnika Copyright (c) 2019 Elektronika ir Elektrotechnika 2019-12-06 2019-12-06 25 6 79 79