Електротехнички факултет [Научни радови] / Faculty of Electrical Engineering [Scientific papers]

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A Comparative Study of Voltage, Peak Current and Dual Current Mode Control Methods for Noninverting Buck-Boost Converter
(Academic Mind, Belgrade, 2016) Bošković, Marko Č.
This paper presents a comparison of voltage mode control (VMC) and two current mode control (CMC) methods of noninverting buck-boost converter. The converter control-to-output transfer function, line-to-output transfer function and the output impedance are obtained for all methods by averaging converter equations over one switching period and applying small-signal linearization. The obtained results are required for the design procedure of feedback compensator to keep a system stable and robust. A comparative study of VMC, peak current mode control (PCMC) and dual-current mode control (DCMC) is performed. Performance evaluation of the closed-loop system with obtained compensator between these methods is performed via numerical simulations.
A robust control design for multi-input LTI systems using discrete-time arbitrary order sliding mode approach
(Elsevier, 2024) Peruničić-Draženović, Branislava; Milosavljević, Čedomir; Huseinbegović, Senad; Veselić, Boban; Petronijević, Milutin
This paper proposes a robust digital sliding mode control design for multi-input linear systems that provides the closed-loop system dynamics of an arbitrary order having a specified feasible spectrum of poles. By appropriate selection of auxiliary outputs according to the controllability indices of the system, the system is decoupled into a set of subsystems. The number of these subsystems is equal to the number of control inputs. The desired dynamic of the considered system is achieved using discrete-time higher order sliding mode, where the discrete-time sliding mode of appropriate order is realized in each subsystem. The robustness is based on the fact that the previous values of the matched disturbances are directly reflected in the present value of the switching variables and it will be enhanced by using an estimator/compensator based on integral of sliding function. This control structure looks like discrete-time super-twisting control. Effectiveness of the proposed control is analyzed and its impact on the control system performances is derived. The proposed control approach is illustrated by simulation examples.
A Survey on Writer Identification and Recognition Methods with a Special Focus on Cultural Heritage
(CEUR Workshop Proceedings, 2022) Ćosović, Marijana; Janković Babić, Radmila; Amelio, Alessia
This paper reviews the state-of-the-art contributions for writer identification and recognition with a special focus on applications in the domain of cultural heritage. The task of writer recognition has only recently been recognized as a problem that can be solved by the methods available in the computer vision domain. A number of researchers have explored the performance of deep learning and transfer learning techniques for writer identification in historical documents, and for this purpose various datasets have been used, including the Avila Bible dataset, Historical-WI, HisFragIR20, IAM, HWDB and others. This paper analyses relevant methods used for writer identification and recognition in historical and medieval documents. It also makes a distinction between classification based on words, patches, or whole pages. The results indicate that the current literature supports using deep learning and transfer learning methods, as they are found to achieve the highest performance.
A telehealth system for automated diagnosis of asthma and chronical obstructive pulmonary dise
(2018) Gurbeta, Lejla; Badnjevic, Almir; Maksimovic, Mirjana; Omanovic-Miklicanin, Enisa; Sejdic, Ervin
This paper presents the development and real-time testing of an automated expert diagnostic telehealth system for the diagnosis of 2 respiratory diseases, asthma and Chronic Obstructive Pulmonary Disease (COPD). The system utilizes Android, Java, MATLAB, and PHP technologies and consists of a spirometer, mobile application, and expert diagnostic system. To evaluate the effectiveness of the system, a prospective study was carried out in 3 remote primary healthcare institutions, and one hospital in Bosnia and Herzegovina healthcare system. During 6 months, 780 patients were assessed and diagnosed with an accuracy of 97.32%. The presented approach is simple to use and offers specialized consultations for patients in remote, rural, and isolated communities, as well as old and less physically mobile patients. While improving the quality of care delivered to patients, it was also found to be very beneficial in terms of healthcare
A Zonal Approach for Wide-Area Temporary Voltage Quality Assessment in a Smart Grid
(MDPI, 2024) Forcan, Miodrag; Simović, Aleksandar; Jokić, Srđan; Forcan, Jovana
Wide-area voltage quality assessment represents one of the mandatory objectives for distribution system operators in the development of advanced distribution management systems supporting smart grid requirements. This paper introduces a zonal approach for wide-area temporary voltage quality evaluation in a distribution network. The concept of temporary voltage quality evaluation and assessment is recommended to incentivize active/online management of voltage quality issues. A decision support system based on simple deterministic rules is proposed for rating the voltage quality zones in a distribution network and making recommendations to the distribution system operator. Voltage RMS level, unbalance, and total harmonic distortion are considered voltage quality indices representing the inputs in the decision support system. Residential, commercial, and industrial load types are considered when setting the thresholds for voltage quality indices. The proposed zonal approach for the division of distribution networks in voltage quality zones is applied to the example of a typical European-type distribution network. The operation of a decision support system is tested using the developed distribution smart grid model. The following simulation case studies are conducted: loads with low power factors, manual voltage regulation at MV/LV transformers, unbalanced loads, integration of solar power plant, and nonlinear loads. The obtained simulation results reveal the benefits of the proposed voltage quality assessment approach. Cybersecurity challenges that may impact the proposed approach are addressed, including security vulnerabilities, data privacy, and resilience to cyber threats.
An Algorithm for transformer hot spot temperature determining
(Wydawnictwo SIGMA - N O T Sp. z o.o., Poland, 2017) JOKIC, Srdjan; MIJIC, Danijel; MATIC, Petar
This paper presents an algorithm for the winding temperature change estimation and the hot spot temperature determining of an oil filled power transformer. The proposed algorithm is based on the functional relation between the change of winding resistance and the measured oil temperature. The temperature changes approximation is based on the method of least squares. The proposed method is applied in the software for a field test instrument and verified by the field experiments.
An Assessment of Extrapolated Field Strengths Versus Distance, Measurement Time, and Induced Traffic From 5G Base Station in C-Band
(Institute of Electrical and Electronics Engineers Inc., 2024) WALI, SANGIN QAHTAN; SALI, ADUWATI; ŠUKA, DARKO; AERTS, SAM; ALKURAYŞI, MOHAMMED; LI, LU; ISMAIL, ALYANI; HASHIM, FAZIRULHISYAM; ALSAIDOSH, YASSER A.; GIL JIMÉNEZ, VÍCTOR P.; RUTTNER, MANFRED; OSMAN, ANWAR FAIZD
This study evaluates the maximum theoretical exposure to radiofrequency (RF) electromagnetic fields (EMFs) from a Fifth-generation (5G) New Radio (NR) base station (BS) while using four commonly used mobile applications: YouTube for video streaming, WhatsApp for voice calls, Instagram for posting pictures and videos, and running a Video game. Three factors that might affect exposure, i.e., distance of the measurement positions from the BS, measurement time, and induced traffic, were examined. Exposure was assessed through both instantaneous and time-averaged extrapolated field strengths using the Maximum Power Extrapolation (MPE) method. The former was calculated for every measured SS-RSRP (Secondary Synchronization Reference Signal Received Power) power sample obtained with a sampling resolution of 1 second, whereas the latter was obtained using a 1-min moving average applied on the applications’ instantaneous extrapolated field strengths datasets. Regarding distance, two measurement positions (MPs) were selected: MP1 at 56 meters and MP2 at 170 meters. Next, considering the measurement time, all mobile application tests were initially set to run for 30 minutes at both MPs, whereas the video streaming test (YouTube) was run for an additional 150 minutes to investigate the temporal evolution of field strengths. Considering the traffic, throughput data vs. both instantaneous and time-averaged extrapolated field strengths were observed for all four mobile applications. In addition, at MP1, a 30-minute test without a User Equipment (UE) device was conducted to analyze exposure levels in the absence of induced traffic. The findings indicated that the estimated field strengths for mobile applications varied. It was observed that distance and time had a more significant impact than the volume of data traffic generated (throughput).
AN INTEGRATED FUZZY AHP AND TOPSIS MODEL FOR SUPPLIER EVALUATION
(University of Belgrade, Serbia, 2016) MAKSIMOVIĆ, Mirjana; MILOŠEVIĆ, Vladimir
Wireless Sensor Networks (WSNs) consist of wireless sensor nodes, where the choice of their deployment scheme depends highly on the type of sensors, their application, and the environment they will operate in. The performance of WSNs can be affected if the network is deployed under different topologies. In this paper various strategies for positioning nodes in WSNs for fire detection (grid, triangular and strip) are discussed. We propose the proper placement of the smoke sensors to satisfy two important network design objectives: to maximize the network lifetime after fire ignition, and to achieve full coverage by using a minimum number of sensors (especially in a deterministic node deployment).
Analysis of the Band-Pass and Notch Filter with Dynamic Damping of Fractional Order Including Discrete Models
(ETF – School of Electrical Engineering, University of Belgrade, 2018) Bošković, Marko; Šekara, Tomislav B.; Rapaić, Milan R.; Lutovac, Budimir; Daković, Miloš; Govedarica, Vidan
The paper presents analysis of the second order band-pass and notch filter with a dynamic damping factor βd of fractional order. Factor βd is given in the form of fractional differentiator of order , i.e. βd=β/s, where β and  are adjustable parameters. The aim of the paper is to exploit an extra degree of freedom of presented filters to achieve the desired filter specifications and obtain a desired response in the frequency and time domain. Shaping of the frequency response enables achieving a better phase response compared to the integer-order counterparts which is of great concern in many applications. For the implementation purpose, the paper presents a comparison of four discretization techniques: the Osutaloup’s Recursive Algorithm (ORA+Tustin), Continued Fractional Expansion (CFE+Tustin), Interpolation of Frequency Characteristic (IFC+Tustin) and recently proposed AutoRegressive with eXogenous input (ARX)-based direct discretization method.
Application of internet of things in food packaging and transportation
(Inderscience Enterprises Ltd, 2015) Maksimović, Mirjana; Vujović, Vladimir; Omanović-Mikličanin, Enisa
Food safety is a scientific field which includes a number of routines and inspections at every stage of the food chain that should be adopted to avoid potentially dangerous health risks. Novel and efficient solutions across the supply chain are the consequence of constant upgrades of information and communication technologies. With the help of internet of things (IoT) connected testing equipment, food quality can be monitored at any point from farm to table, connecting at the same time food producers, transportation and hospitality/retail companies. Relying on the fact that food transporting and packaging units are the most critical points in food production, the survey of IoT applications in food packaging and transportation is given in this paper. To demonstrate the significance of IoT appliance and defined concepts, a proposal of low cost solution based on IoT for real-time food traceability and monitoring in food transportation process is presented.
Application of the Voltage Control Technique and MPPT of Stand-alone PV System with Storage
(2022) HIVZIEFENDIC, Jasna; VUIC, Lejla; LALE, Srdjan; SARIC, Mirza
To provide a stable operation of a standalone microgrid based on the photovoltaic system in the most efficient way, various mechanisms and control strategies need to be engaged simultaneously. Modeling, simulation, and analysis of the microgrid system composed of PV generator, battery energy storage system (BESS), and DC/AC converter are presented in the paper. The PV generator operates in maximum power point (MPP) mode, while the BESS is deployed to enable power flow between the storage and consumers using the charge/discharge cycle of the battery. The maximum power point tracking (MPPT) control at the PV side, combined with battery control, is obtained by Perturb and observe (P&O) and Fuzzy Logic Control (FLC) algorithms. Simulation based voltage control strategy is performed by using both DC/DC buck-boost converter and DC/AC converter with aim to obtain stable voltage for different power inputs. Modeling and simulations are performed in MATLAB/Simulink software. It is demonstrated that proposed methods ensure a stable microgrid operation and PV system operation in MPP mode. Both MPPT algorithms, P&O and FLC, provided accurate responses with very high efficiency above 95%.
APPLICATION OF TIME-AVERAGED AND INTEGRAL-BASED MEASURE FOR MEASUREMENT RESULTS VARIABILITY REDUCTION IN GSM/DCS/UMTS SYSTEMS
(Oxford University Press, 2019) Šuka, Darko; Pejović, Predrag; Simić-Pejović, Mirjana
Since EMF levels from wireless telecommunication networks are non-stationary and exhibit large temporal variations, the use of continuous measurements during extended periods (preferably 24 h or longer) with a data-logging system is required. Because of the short-term variations of E field, the 6-min measurements and 6-min averaged results to obtain the mean level strength at a given place appear to be dependent on the time of measurements during the day. This paper presents a new (integral-based) measure to evaluate electromagnetic exposure. The new measure is a pure physical descriptor of the amount of exposed energy density (a parameter accumulated from instantaneous power density values in time). To confirm previous observations, continuous measurements with personal exposure metre were recorded 24 h a day for two weeks at every location in urban area, 14 different locations in total. Additionally, to check temporal variations and repeatability of exposure assessment, a week of prolonged measurements was taken 6 months later, making in total three weeks of measurements at 2 locations. Day-to-day repeatability of RF-EMF exposure was analysed through the time-averaged and integral-based measure. The analysis is based on approximately 5.1 million data samples (1.7 million for each band). The ratio between the maximum and minimum instantaneous (maximum and minimum 6-min averaged) E field values during the day could reach up to 25 dB (20 dB). Therefore, great variability in the results may occur. By applying the 24 h time-averaged and integral-based measure on a 24 h data set of measurements, the variability of daily exposure could stay within ±20% of the week mean level obtained either with the time-averaged or integral-based measure. Both, the time-averaged E field and integral-based power density exposures of the general public in all locations were found to be well below the general public exposure limits of the ICNIRP guidelines.
BGP Anomaly Detection with Balanced Datasets
(University of Osijek, 2018) OBRADOVIĆ, Slobodan; ĆOSOVIĆ, Marijana
We use machine learning techniques to build predictive models for anomaly detection in the Border Gateway Protocol (BGP). Imbalanced datasets of network anomalies pose limitations to building predictive models for anomaly detection. In order to achieve better classification performance measures, we use resampling methods to balance classes in the datasets. We use undersampling, oversampling and combination techniques to change class distributions of the datasets. In this paper we build predictive models based on preprocessed network anomaly datasets of known Internet network anomalies and observe improvement in classifier performance measures compared to those reported in our previous work. We propose to use resampling combination techniques on datasets along with Decision Tree and Naïve Bayes classifiers in order to achieve the best trade-off between (1) the F-measure and the length of model training time, and (2) avoiding overfitting and loss of information
BGP Anomaly Prediction Using Ensemble Learning
(2019) Cosovic, Marijana; Junuz, Emina
This paper investigates anomalies such as worms, power outages, and routing table leak (RTL) events occurring in Border Gateway Protocol (BGP) that can cause connectivity and data loss issues. Ensemble learning is a machine learning model employing multiple classifiers in order to reliably identify network anomalies. We use bagging, boosting, and random forests ensemble models trained on network anomaly datasets for classification improvement. Models were compared with respect to the following performance metrics: F-measure, Matthews correlation coefficient (MCC), Receiver operating characteristic (ROC) curve, precision-recall (PR) curves and model execution time. We observed improvement in performance measures when ensemble classifiers realized in Python were used in comparison to our previously reported results on single classifiers. Further improvement in most performance measures was observed by using sampling techniques (oversampling and undersampling) on anomalous datasets. This approach increases model execution time which is not favorable for real-time anomaly detection models.
Cloud-based System for Real-Time Reading of Smart Meters’ Data over 5G New Radio
(2021) Forcan, Miodrag; Maksimović, Mirjana; Forcan, Jovana; Jokić, Srđan
The potential of the combined application of Cloud computing and the fifth generation of cellular network technology (5G) in Smart Grid (SG) could be revolutionary in terms of empowering the Advanced Metering Infrastructure (AMI). The model of a real-time 5G-based communication system for remote reading of Smart Meters’ data is developed and presented in this paper. Online monitoring of power demand has been performed using the Cloud-based platform ThingSpeak. The proposed 5G communication model and online monitoring function have been tested and validated using a power demand variation scenario in a well-known IEEE 13 node network. The obtained results confirm the model accuracy and reveal the potential of AMI based on realtime data transmission between Smart meters (SM) and Cloud computing platform using a 5G communication network.
DESIGN OF ESP COURSE FOR GROUPS OF STUDENTS FROM DIFFERENT DEPARTMENTS WITHIN HUMANITIES AND SOCIAL SCIENCES
(University of Niš, Serbia, 2023) Kovačević, Darko
In today’s practice of teaching ESP at the university level, especially at the faculties with a great number of departments, it sometimes happens that the students from different departments are grouped to attend ESP lessons. Such a situation occurs due to different circumstances and conditions, such as a disproportional number of students at individual departments, the number of allocated lessons per week, classroom organization of the teaching process, etc. The paper will present, elaborate and discuss, the design of an ESP course for groups consisting of students from different departments within humanities and social sciences, in the duration of four semesters (four subjects, two academic years), with a special emphasis on the selection and creation of course materials. In doing that, both relevant and current ESP literature and practical experiences will be used. The outcome of the paper will be the creation of a detailed course plan, containing all the components relevant to its practical application.
Development of Integral Environment in Matlab/Simulink for FPGA
(VSB-Technical University of Ostrava, Czech Republic, 2014) JOKIC, Dejan; LABURA, Slobodan; STANKOVSKI, Stevan
In this paper is presented realization of integral environment which consists of software and hardware components for the purpose of programming Altera DE boards. Software component is Toolbox FPGA Real Time which enables simple use of Matlab/Simulink with DSP Builder for the purpose of realization of control structures. Hardware component are Interface cards that make connection of DE board with object of control possible. Simulation and experimental results of DC motor control indicate the usefulness of the proposed concept.
Experimental Evaluation of Distortion Effect for Grid-Connected PV Systems with Reference to Different Types of Electric Power Quantities
(MDPI, 2022) Ikić. Marko; Mikulović, Jovan
Aware of the fact that the installed PV capacity and its power production rapidly increased in the last decade, with the huge impact that has been done to the power system, the distortion effects for grid-connected PV systems with reference to different types of electric power quantities will be presented in this article. The impact of the frequent fluctuation of solar irradiance on the behavior of the grid-connected PV system, due to cloud movements and resulting shadows and in terms of power quality and the evaluation of power components, is the topic of analysis in this research. Besides the simulation results of certain study cases, an experimental evaluation of electric power quantities on an actual PV system in real weather conditions was also performed. The experimental setup, formed through the combination of a PC and multifunctional I/O board with an appropriate software solution, was established and used for obtaining the target results. The methodology used for the evaluation of electric power quantities relied on the current physical components (CPC) theory for power definition. The experimental results were obtained for three different cases, namely, the low, medium, and high solar irradiance cases. On the basis of these results, the conclusions about distortion effects are given.
Fast and Reliable Locating of Points with the Maximum Value of Total Electromagnetic Fild Using a Modern Experimental Method for Radio Coverage in Urban Environment
(Hindawi, 2014) Medjedovic, Petar S.; Suka, Darko S.
This research has been performed within the project “prediction, measurement, and analysis of composite electromagnetic field of artificial radiation sources,” funded by theMinistry of Science and Technology of the Republic of Srpska, Bosnia and Herzegovina. The ultimate goal of the project is the installation of a monitoring network for continuous measurement and recording of nonionizing electromagnetic (EM) radiation levels in the wider area of Banja Luka city centre covering about 10 km2. For this reason it was necessary tomake an optimal choice from a dozen ofmeasurement points with themaximumvalue levels of total EM field. It was a difficult task, because in this case, with the resolution of 5m× 5m, approximately 400,000 points should be examined. Therefore, the pedestrian zones, areas, and routes with significantly smaller surfaces but with the largest flow of people have been examined, so the time required for their mapping with values of total EM field has been reduced to a more realistic framework. In this paper, in the volume allowed by the defined criteria, a fast and reliable experimental method has been described, which has been examined at one of the studied areas in the named project, with surface of 0.008 km2.
Game-Based Learning in Museums—Cultural Heritage Applications
(MDPI, 2020) Ćosović, Marijana; Ramić Brkić, Belma
As traditional museums migrate to the virtual world, they offer wider access to the exhibit collections but often fail to present content of those collections in more engaging way. Game-based learning is one of the solutions to mitigate this inevitable transition and support active learning in the process. It is increasingly gaining interest from the cultural heritage scientific community for the purpose of promoting cultural heritage, raising awareness of its importance and motivating users to visit cultural institutions such as museums more often. There are numerous examples of serious games that are based on or contain heritage content. Tangible cultural heritage is more represented in the virtual worlds and mainly based on applications of 3D technology. Recently, intangible cultural heritage is gaining more visibility within cultural heritage scope as a domain in which game-based learning could assist in its preservation. This paper attempts to address pros and cons of game-based learning in general and reflect on the choices of using serious games in the museum environment.

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