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XI NATIONAL CONFERENCE
WITH INTERNATIONAL PARTICIPATION
ELECTRONICA 2020
PROGRAMМЕ
23 – 24 July 2020
Sofia
National Science and Technical Centre
108 Rakovski Str.
&
Virtual rooms
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XI NATIONAL CONFERENCE WITH INTERNATIONAL
PARTICIPATION “ELECTRONICA 2020”
Organized by:
The Union of Electronics, Electrical Engineering and
Telecommunications (CEEC),
Technical University of Sofia (TU-Sofia),
IEEE Bulgarian Section,
and Faculty of Electronic Engineering and Technologies (FEET)
In cooperation with:
Federation of the Scientific and Technical Unions in Bulgaria (FNTS),
Bulgarian Academy of Sciences (BAS),
University of Applied Sciences - Offenburg,
Riga Technical University,
VDE – Germany and
Leading Electronics Companies.
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XI NATIONAL CONFERENCE WITH INTERNATIONAL
PARTICIPATION “ELECTRONICA 2020”
Honorary chairmen:
Ivan Kralov – TU - Sofia
Ivan Yatchev – FNTS and CEEC
Conference chairmen:
Ivo Iliev - TU Sofia
Seferin Mirtchev – СЕЕС
Georgi Mihov – BAS and TU - Sofia
Scientific Secretary:
Dimitar Arnaudov – TU - Sofia
Local Organizing Committee:
Nikolay Hinov – TU - Sofia
Emil Manolov – TU - Sofia
Oskars Krievs - RTU
Sanka Gateva - BAS
Georgi Stoyanov - IEEE Bul. Sec.
Anatolii Aleksandrov - TU - Gabrovo
Ilia G. Iliev - TU-Sofia
Dimitar Yudov – BFU - Burgas
Rossitza Goleva - IEEE Bul. Sec.
Radi Romanski – СЕЕС
Ivan Vassilev - CEEC
Rossen Radonov - ТУ - Sofia
Anna Andonova - TU - Sofia
Nikolay Madzharov - TU - Gabrovo
Petar Yakimov - TU - Sofia
George Angelov – TU - Sofia
Vencislav Valchev -TU -Varna
Sotir Sotirov - University "Prof. As. Zlatarov"
Bourgas
Krassimir Paskalev – Kostal SofiaSoft Bulgaria
Georgi Atanasov - Festo production
Sylvain Collot -Melexis Bulgaria
Verka Alexieva - LEM Bulgaria
Ivan Mihaylov - Visteon
Nikola Durchev - Balkantel
Nikolay Iliev – Next Lab
Krasimir Pingelov - Electron Progress
Program Committee:
Alden Dochshanov, Italy
Darius Andriukaitis, Lithuania
Davy Pissoort, Belgium
Dimitar Arnaudov, Bulgaria
George Angelov, Bulgaria
Gennady Zinoviev, Russia
Ivo Iliev, Bulgaria
Juraj Breza, Slovakia
Lykourgos Magafas, Greece
Leonids Ribickis, Latvia
Marin Marinov, Bulgaria
Marin Hristov, Bulgaria
Miglena Dontschewa, Austria
Sia Lozanova - BAS
Namyong Kim, Korea
Nicolae Muntean, Romania
Nikolay Hinov, Bulgaria
Octavian Cornea, Romania
Reinhard Bauer, Germany
Stefan Hensel, Germany
Stoyan Stoyanov, UK
Vladislav Skorpil, Czech Republic
Zenon Gotra, Ukraine
Tzeno Galchev, USA
Vassil Palankovski, Austria
Viera Stopjaková - Slovakia
Ritonja Jozef - Slovenia
Secretariat
Stefan Patchedjiev – СЕЕС
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XI NATIONAL CONFERENCE WITH INTERNATIONAL PARTICIPATION
“ELECTRONICA 2020”
Hour Event Discussion
Wednesday
22 July 15.00-18.00
Registration of participants & test
the system (Virtual room 1)
Webex software
10.00-10.30 Opening Session
Hall 3 & Virtual room 1
10.30-12.00 Scientific Session 1
Hall 3 & Virtual room 1
Virtual room 2
Virtual room 3
12.00-12.30 Lunch break
12.30-14.15 Scientific Session 2
Hall 3 & Virtual room 1
Virtual room 2
Virtual room 3 Thursday 14.15-14.30 Coffee break
23 July 14.30-15.45 Invited papers
Hall 3 & Virtual room 1
16.00-17.00
“University education in automotive
electronics and business needs".
Hall 3 & Virtual room 1
17.00-18.00 „Alumni meeting”
Informal discussion
Hall 3 & Virtual room 1
Friday
24 July
09.00 -10.15
Scientific Session 3
Hall 3 & Virtual room 1
Virtual room 2
Virtual room 3
10.15 -10.30 Coffee break
10.30 -12.00 Scientific Session 4
Hall 3 & Virtual room 1
Virtual room 2
Virtual room 3
12.00 -12.30 Lunch break
12.30-14.00 Scientific Session 5
Hall 3 & Virtual room 1
Virtual room 2
Virtual room 3
14.00 -14.30 Invited papers
Hall 3 & Virtual room 1
14.45 -16.00 Scientific Session 6
Hall 3 & Virtual room 1
Virtual room 2
Virtual room 3
16.00 -16.15 Coffee break
16.15 -17.30
Scientific Session 7
Hall 3 & Virtual room 1
Virtual room 2
Virtual room 3
17:30 Closing Session
Hall 3 & Virtual room 1
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Opening Session 10.00 - 10.30.
Hall 3 & Virtual room 1, Thursday 23 July 2020
Scientific Sessions 1, 2 10.30 -14.15
Hall 3 & Virtual room 11, Thursday 23 July 2020
Invited papers 14.30 – 15.45
Hall 3 & Virtual room 1, Thursday 23 July 2020
Design of Virtual Calibrator for Teaching Metrology in Higher Education Zivko KOKOLANSKI and Petar VIDOEVSKI - “Ss Cyrilu and Methodius”
University in Skopje
Е-mobility: looking into the technology "under the cover"
Krasimir PASKALEV and Zlatko Zlatkov- KOSTAL SofiaSoft Bulgaria
Discussion 16.00 -17.00
Hall 3 & Virtual room 1, Thursday 23 July 2020 "University education in automotive electronics and business needs".
Alumni meeting, Career forum
Virtual rooms
Scientific Sessions 3, 4, 5 9.00-14.00
Hall 3 & Virtual room 1, Friday 24 July 2020
Invited papers 14.00 - 14.30
Hall 3 & Virtual room 1, Friday 24 July 2020
WBG semiconductors, interleaving and integration of magnetics for non-isolated
DC-DC converter performance improvement Kaspars KROICS - Riga Technical University
Scientific Sessions 6, 7 14.45-17.00
Hall 3 & Virtual room 1, Friday 24 July 2020
Closing Session 17.30
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Scientific Session 1
Information and Communication Technologies
Hall 3 & Virtual room 1, Thursday 23 July, 10.30 - 12.00
Chairpersons: Seferin MIRTCHEV, Stefan PATCHEDJIEV
1.1. MACHINE LEARNING APPROACH FOR MAGNETIC FIELD CALCULATIONS Valentin Mateev, Iliana Marinova
Abstract – Here is presented a machine learning approach for 2D steady-state and harmonic
magnetic field calculations based on Poisson and Helmholtz equations for Dirichlet boundary
problems. The approach is implemented on multilayer convolutional neural network trained over
the Compumag 1b T.E.A.M. benchmark problem variations dataset. Implementation is suitable for
non-homogeneous magnetic properties domains and distributed excitation sources. Results
accuracy is estimated in comparison with Finite Element Method model of the same problem.
1.2. OPTIMIZATION OF TORQUE AND POWER DENSITY FOR COAXIAL MAGNETIC GEARS
Valentin Mateev, Iliana Marinova
Abstract – In the present work, the recent positive trend in torque and power density of the
coaxial magnetic gears is discussed. Timeline of magnetic gears development according to design
topology and magnetic materials improvements is presented. Five generations of magnetic gears
are recognized according to the torque density limitations. Analysis of possible design and material
improvement opportunities is made. Main approach for torque and power density improvement is
the maximization of the air-gap surface in magnetic gear volume. For coaxial magnetic gears this is
possible by implementation of conical and multistage rotor designs. Theoretical limitations in case
of conical and multistage rotors usage are considered.
1.3. AN ORIGINAL AND SIMPLE METHOD FOR STUDYING THE PERFORMANCE OF A VoIP NETWORK
Ivan Nedyalkov
Abstract – In the present work, an easy and simple method for estimating the working capacity
of VoIP networks, using a protocol analyzer and mathematical distributions for the moments of
arrival of the packets, is proposed. The parameter that is monitored through the protocol analyzer
is the jitter. The mathematical distribution and approximations give an additional idea of the time
delay in the observed network. A virtual network is created to verify the proposed method.
Simulation studies are carried out to test the proposed method. The results of using the method are
presented.
1.4. PROGRAMMABILITY OF CHARGING FUNCTIONALITY AT THE NETWORK EDGE
Evelina Pencheva, Ivaylo Atanasov, Aleksandar Nametkov
Abstract – Programmability is a key characteristic of next generation networks. It enables open
access to network functions for external applications. In this paper, an approach to open access to
charging functions at the network edge is proposed. The approach is based on Multi-access Edge
Computing (MEC) technology which distributes cloud capabilities in the vicinity of end users. The
co-location of MEC with distributed core functions makes it possible to open the network interfaces
for advanced applications. The paper presents a new MEC service which enables applications to
charge the end users by amount or volume. The service design follows the Representational State
Transfer architectural style. The service resources and supported methods are described, and the
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service feasibility is illustrated by modeling the charging status as seen from the network and
application points of view.
1.5. TOWARD NETWORK INTELLECTUALIZATION IN 6G Evelina Pencheva, Ivaylo Atanasov, and Ivaylo Asenov
Abstract – After the first deployments of fifth generation (5G) networks, research on 6G system
has begun. The paper summarizes the characteristics of future 6G services and applications,
presents an overview of enabling technologies and focuses on the role of artificial intelligence
in improving end user quality of experience and in network optimization.
1.6. AN APPROACH FOR SECURING MQTT PROTOCOL IN ESP8266 WIFI MODULE
Iordan Stoev, Snezhinka Zaharieva, Adriana Borodzhieva, Gergana Staevska
Abstract – The paper presents an approach fo communication between ESP8266 modules
based on MQTT protocol using simple non-secure class for implementing the WiFi protocol.
Encryption based on Advanced Encryption Standard – 256-bit symmetric encryption algorithm was
implemented in order to achieve simple secure communication. In addition, a pseudorandom
generator was used to introduce asymmetry of the cypher data transmitted through the protocol.
1.7. COMPARATIVE ANALYSIS OVER DIFFERENT DEGREE OF JPEG COMPRESSION USED IN CBIR SYSTEMS
Miroslav Marinov
Abstract – Content-bases image retrieval systems (CBIR) use computer vision methods for
organizing, analyzing, processing and searching of million graphic files uploaded in the internet
daily. For that reason, the retrieval process is a key element in CBIR applications. The best system
performance is based on accurate and complete search which must be finished in reasonable
amount of time. It is straightly related to extracting, storing, and indexing of all necessary metadata
from the examined image set.
This paper gives information about JPEG compression and how it is used in some of the most
widespread CBIR systems. It reveals how different degree of that compression influences the
generated results from custom developed CBIR application. Furthermore, it shows the various of
similarity between same image set but examined in two different ways – with non-compressed and
compressed data retrieved by the system. At the end, the conclusions are made based on generated
results from developed and tested CBIR application which was made for these purposes.
1.8. DEVELOPMENT OF ULTRA-LOW POWER SENSOR NODE USING FRAM AND NANO TIMER
Dimitar Tokmakov, Stanislav Asenov
Abstract – In this paper we presents a project of ultra-low power sensor node for IoT
applications with LoRaWAN interface, successfully designed and tested. The main features of this
design is its ultra-low power consumption of sensor node in sleep mode, long distance
communication and secure data transmission. By using external nano timer TPL5110 and FRAM
(Ferroelectric Random Access Memory), it is possible to reduce the sensor node sleep mode
consumption current Ic to only 45nA. This increases battery life and sensor node autonomous
operation for several years.
1.9. INFORMATION TECHNOLOGY SUPPORT FOR PORTFOLIO OPTIMIZATION Todor Stoilov, Krasimira Stoilova
Abstract – The paper describes an application of information technology to support decision-
making for portfolio optimal investment. The decision making task is formalized as a portfolio
optimization problem solved in Excel environment, which gives practical tool for implementation
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for the decision-making. The portfolio optimization applies maximization of Net Present Value,
because the riskless return is close to zero. The derived information technology solution is
numerically tested with mutual funds, traded on the Bulgarian Stock Exchange for 2019.
1.10. PROBLEMS WITH ANTENNA RADOME BEHAVIOUR AT LOW ELEVATION DIRECTIONS
Plamen Dankov, Yavor Zhelev, Ivaylo Slavkov
Abstract - The paper discusses some practical problems appearing at very low elevation
directions in electronically steerable antennas for wireless communication, caused by the used
multilayer antenna radome. The experimental and numerical results show how the polarization of
the received/ transmitted signals changes through the radome at big incident angles ~60-80 deg.
The measured anisotropy of different radome materials and layers confirms the origin of the
observed effects. Finally, useful conclusions are presented.
1.11. THE IMPACT OF MACHINE VISION IN ADDITIVE MANUFACTURING Roumiana Ilieva, Mario Nikolov
Abstract - Digital manufacturing (DM) is a key strategy that plays strategies in planning
toward the knowledge-based manufacturing. Combining 3D machine vision (3D-MV) and an
Additive Manufacturing (AM) is one of the innovative approaches in manufacturing. Cutting-edge
systems will enable 3-D printing machine users to accurately test and qualify printed parts for any
number of applications, including aerospace and medical devices.
1.12. IT SERVICE MANAGEMENT FRAMEWORK TO IMPROVE BUSINESS INFORMATION STRUCTURE
Roumiana Ilieva, Yoto Nikolov
Abstract - The objective of our study is to come to an understanding on the benefits provided by
the implementation of IT service management Framework in business IT structure. One of the most
commonly used by hundreds of organizations framework for IT service management is ITIL. ITIL is
not a standard that has to be followed, it is more like a guidance that should be read and
understood and used to create value for the service provider and its customers. Business is advised
to adopt ITIL best practice and to adopt them to work with their specific environments to meet their
needs. Here we will compare challenges and benefits of companies at various levels of
implementing IT service management frameworks, also looks at the number of implemented
processes at the various levels. Where the results indicate that as the maturity of implementation
increases, the perception of challenges decreases.
Scientific Session 2
Circuits and Systems
Hall 3 & Virtual room 1, Thursday 23 July, 12.30 - 14.15
Chairpersons: Ivo ILIEV, Georgi NIKOLOV
2.1. AN ADAPTIVE CONTROL SCHEME FOR HUMAN FOLLOWING BEHAVIOR OF MOBILE ROBOTS
Plamen Petrov, Veska Georgieva, Ivan Kralov, Stilyan Nikolov
Abstract – In this paper, we present an adaptive mobile robot control scheme for autonomous
human following, such that the robot keeps a desired distance from the person. A human-robot
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interaction model in error coordinates suitable for robot following applications is proposed. An
adaptive control low is presented to tackle with the problem of the unknown human velocity.
Simulation and experimental results are presented to illustrate the effectiveness of the proposed
control scheme.
2.2. METHODOLOGY FOR FREQUENCY OF POWER-LINE INTERFERENCES MEASURING
Georgy Mihov, Dimiter Badarov
Abstract – A test procedure for mains interference frequency measuring is represented in the
work. The procedure is based on measurement the transfer coefficient of an averaging digital filter
applied to the interference signal. The procedure is implemented in MatLab environment. It
includes filters for elimination the mains interference extracting, for suppression the third harmonic
and for measuring the power-line interference frequency. Appropriate experiments has been
investigated.
2.3. MODELING THE ELECTRICAL PARAMETERS OF A MULTI-STAGE THERMOELECTRIC MODULE BY NEURAL NETWORK
Todor Petkov, Ivaylo Belovski, Kaloyan Ivanov and Anatoliy Aleksandrov
Abstract – This work presents the results of modeling the electrical parameters - current I and
voltage E of a multi-stage Peltier module working in generator mode using a neural network. A
preliminary experiment was performed to accurately determine the current and voltage generated,
depending on the applied temperature difference ΔT and load resistance R. The values obtained
were used to train the neural network.
2.4. OPTIMIZATION OF SYSTEM DEVELOPMENT PROCESS FOR ELECTRONIC DEVICES IN THE AUTOMOTIVE INDUSTRY
Dimitar Vrachkov and Dimitar Todorov
Abstract – The main object of the current research will be the optimization of the system
development process for electronic devices in the automotive industry. The material is based on the
main mechanisms for electronic development from the international SPICE standard. We will take a
look over three main problems in the automotive industry today and we will try to provide good
solution to all of them. First topic is more or less overview of the current situation with the
documentation in the automotive - what are the specifics of designing electronic devices for the
automotive industry? Also, we will provide solution for monitoring of the results related to specific
system requirements. At the end, we will try to define optimization strategy for the development
process – without losing traceability and without losing project quality.
2.5. ACTIVE RC LPFS WITH SINGLE-ELEMENT POLE FREQUENCY TUNING
Darya Denisenko, Nikolay Prokopenko, Nikolay Butyrlagin
Abstract – New low-pass filter (LPF) architectures based on differential difference
operational amplifiers (DDOA) are considered. The feature of the proposed LPF is that when
tuning the cut-off frequency, the LPF gain remains unchanged at zero frequency. As a tuning
element, it is possible to use digital potentiometers. The basic equations for two LPF modifications
are presented, which provide parametric synthesis of circuits are discussed. In Micro-cap CAD was
given the results of computer simulation of tunable responses.
2.6. DESIGN FEATURES OF THE SECOND-ORDER ACTIVE BAND-PASS FILTERS WITH INDEPENDENT ADJUSTMENT OF CRITICAL PARAMETERS
Darya Denisenko, Nikolay Prokopenko, Evgeniy Butovka
Abstract – Currently, it is urgent to develop a new generation of active RC filters, which
allow independent tuning of the critical parameters. This makes it easier to build new devices. The
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article first time considers the generalized architecture of new population of the active RC band-
pass filters (ARCFs) in which the independent adjustment of the critical parameters in the pass
band is possible. As an example the equations for the transfer functions and their coefficients for
two new ARCF modifications are given, which allow for the parametric synthesis of the definite
design solutions. The results of modeling in the Micro-CAP program are discussed, confirming the
advantages of the ARCF of the considered family.
2.7.
2.8. DEVELOPMENT AND IMPLEMENTATION OF A DEMONSTRATION MODEL OF SMART PARKING WITH LORA-BASED COMMUNICATION
MODULE
Krasen Angelov,
Abstract– The main purpose of this work is to present the development and implementation of
a demonstration model of smart parking system that uses energy efficient LoRa-based transmission
module, autonomous power supply and the ability for integration into a scalable smart platform for
intelligent provision, monitoring, visualization and management of parking services in large cities
with complex urban environment.
2.9. A COMPARATIVE STUDY OF ENERGY STORAGE SYSTEMS FOR ENERGY HARVESTING DEVICES –
Dimitar Nikolov
Abstract – This paper, presents a model to predict the energy output from reverse
electrowetting energy harvesting system with use of cost-effective materials. Reverse electrowetting
on dielectric allows energy to be harvested from spontaneous aperiodic mechanical movements,
where conventional energy harvesting approaches are not suitable for due to low energy
conversion efficiency and frequency .
2.10. INNOVATIVE TEACHING ON PHOTOVOLTAIC GENERATION Alessandro Ciocia, Paolo Di Leo, Gabriele Malgaroli, Angela Russo, Filippo
Spertino, and Slavka Tzanova
Abstract – One of the most important technologies for the renewable energy production is the
Photovoltaic (PV) one. In the last decades, the enormous growth in the world of Photovoltaic
installation capacity, and future trends, makes the knowledge of this topic fundamental for
engineers working in the energy field with this competence, and not only. Thus, for students
enrolled in industrial engineering courses, appropriate and innovative teaching methods are
necessary. This paper aims to describe the structure of the course “Photovoltaic Power
Generation” in which solar resource and the photovoltaic generators, including power electronics,
are explained. The topics of traditional theoretical lectures are presented, with the links to practical
exercises and laboratories.
2.11. A COMPARATIVE ANALYSIS OF VARIOUS FILTERS FOR NOISE REDUCTION IN CARDIAC ULTRASOUND IMAGES
Veska Georgieva and Anna Grozeva
Abstract – The cardiac ultrasound (US) images are used to obtain qualitative information on
the outline of the organ and type of tissue, as well as quantitative information on the thickness and
movement of the internal walls and layers of the heart. Speckle noise generally masks the fine
details of the US image and makes its interpretation difficult for medical diagnosis. This paper
presents various filters for noise reduction in cardiac US images, which have been discussed and
compared.
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2.12. BODY SENSOR NETWORK FOR REMOTE MONITORING OF PATIENTS' CARDIAC STATUS
Evgeniya Gospodinova, Mitko Gospodinov, Galya Georgieva-Tsaneva, Krasimir
Cheshmedzhiev
Abstract – The article presents a wearable medical electronic system - body sensors network
(BSN), intended for real-time monitoring of physiological parameters of the patients. BSN is
compact platform for sensory registration of cardio rhythm, body temperature, etc. The sensors are
miniature devices for detection of physiological parameters. The transmitted information is stored
in real-time in a wearable “hub” communicating wirelessly with computerized equipment. The
information obtained can be used for individual monitoring of health status, disease warnings and
feedback.
Scientific Session 3
Industrial and Power Electronics
Hall 3 & Virtual room 1, Friday 24 July, 9.00 - 10.15
Chairpersons: Nikolay HINOV, Dimitar ARNAUDOV
3.1. COMPARISON OF CONTROL METHODS FOR BIDIRECTIONAL DC/DC CONVERTERS
Vladimir Dimitrov and Nikolay Hinov
Abstract – This paper considers the use of ripple and compensator based control circuits in
bidirectional dc/dc converters. Typical review of ripple based controllers includes their application
in unidirectional controllers. Their advantages in terms of better transient response, simple
realization and in some cases better efficacy at lighter loads are widely considered. Such a
comparison must be made in the specific case when the application requires bidirectional and more
importantly multiphase operation. This paper investigates by comparing three cases of a control
system- standard compensator based, a constant frequency valley ripple based controller and an
enhanced version including better regulation. These are compared for different voltage sources at
their outputs in term of their regulation and dynamics.
3.2. MATHEMATICAL MODELING AND SIMULATIONS OF DC/DC CONVERTER IN PSIM ENVIRONMENT
Gergana Vacheva and Nikolay Hinov
Abstract – In the current paper mathematical modeling and simulation of DC/DC converter
for educational purposes are presented. It is reviewed the main possibilities of modeling in PSIM
environment. The main libraries and tools are described. The mathematical model of buck
converter with variation of the values of the inductor and the capacitor are presented.
3.3. AREA MEASURING WITH PC CAMERA Petar Panaiotov, Goran Goranov and Valentina Rankovska
Abstract – Area measurement and registration in different areas of the industry are done by
different methods. One example is the production of leather. The opposite shape, different thickness,
and color of the leather make this task a challenge. In the leather industry, a measurement method
using photosensors and a video camera method have been successfully implemented. This article
presents the development of software that measures the area of leather with a USB camera. Such a
system is implemented but it is necessary to manually set the measurement mode. It works by the
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method of dark and light spots and so dark (black) or light (white) skins are measured. The
proposed new software is based on automatic color recognition against a green background.
3.4. USING MARKOV’S CHAINS FOR RELIABILITY MODELING OF ENERGY STORAGE DEVICES
Prodan Prodanov and Dobroslav Dankov
Abstract – The reliability of energy storage devices can be defined by using the State Analysis
Method. For any given system, a Markov model consists of a list of the possible states of that
system, the possible transition paths between those states, and the rate parameters of those
transitions. Those states could be reduced to: operability, failure, protection, availability and
redundancy. To do that type of analysis, Markov Analysis is used, which allows the design of
reliability analysis models that could be used for enhancing the reliability of energy storage
devices.
3.5. RELIABILITY ESTIMATION OF MOSFET TRANSISTORS IN DEPENDENCY OF THERMAL RESISTANCE OF COOLING SYSTEM
Prodan Prodanov
Abstract – MOSFET transistors are elements that appear one of the most widely used types in
industrial electronics. Their reliability assessment is linked to a number of analyses related to the
circuits they are used in, the operating electrical and thermal modes, and the operating conditions.
The present paper studies the impact of the cooling sink in water cooling systems used for cooling
MOSFET transistors in industrial energy conversion systems.
3.6. A STUDY OF THE BOUNDARY MODES OF AN LLC DC/DC CONVERTER OPERATING ABOVE RESONANT FREQUENCY
Aleksandar Vuchev , Tsvetana Grigorova
Abstract – The paper presents the results from investigations of the performance of an LLC
resonant DC/DC converter operating above resonant frequency, including boundary modes (no-
load and short circuit) using the state-plane techniques. Comparative data from calculated and
simulated results are presented.
3.7. Analysis and Investigation of an Asymmetric Bridge Converter for a Three-Phase 12/8 SRM in Generating Mode
Dimitar Yankov , Tsvetana Grigorova
Abstract – The paper presents an analytical and simulation study of an asymmetric bridge
converter fed 12/8 three-phase SRM in generating mode. The main purpose of the investigations is
to clarify the conditions for achieving the maximum energy recovery. It is shown that the amount of
energy returned from the SRM to the battery depends mainly on the excitation and generation
intervals, the PWM dutycycle, the matching of the internal battery resistance and the position-
dependent SRM equivalent resistance. The obtained analytical results in MATLAB/Simulink are
verified.
3.8. COMBINED FOOTPRINT WITH JET PRINTING AND SOLDERING IN THE VAPOR PHASE
Valentin Tsenev, Valentin Videkov
Abstract – The paper presents obtaining a combined footprint [1, 2] of two or more solder
pastes [3, 4] using a jet printer [5]. When using the Pin in Paste (PiP) technology [6] with over
printing [7], two problems arise - obtaining solder balls outside the solder pads [8] and not
everywhere melting of the solder paste. To avoid these problems, a combined footprint of two solder
pastes could be used, which can reduce the melting temperature and collect the solder material in
the pad. Combined footprints were realized by means of a Jet printer on different pads with
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different content of the two solder pastes. Using the reflow process [9] in the vapor phase [10], the
soldering was performed. It was studied and evaluated how the solder material melted in different
sized pads and at different contents of the two solder pastes. The soldering of SMD [11] and TH
[12] elements was also observed and evaluated using a combined fingerprint.
3.9. A Methodology for Analysis of Thermal Transfer by Xray Study Valentin Tsenev
Abstract - The paper presents a methodology for analyzing thermal transfer using Xray
study[1]. The essence of the methodology lies in a detailed analytical survey of the entire thermal
transfer system of a SMD[2] mounted powerful LED by 3D Xray[3] examination of all thermal
transitions. The thermal transfer in the mechanical system of the mounted LED[4] to a printed plate
with a thick aluminum base is described in detail. In the present study, the influence of the quality of
the solder[5] on the thermal transfer at the generated temperature from the LED crystal to the
aluminum substrate was taken into account, and the influence of the voids[6] content was analyzed.
The influence of other thermal transitions is also considered. The results are presented and
conclusions are drawn as to the causes and location of the faulty heat transfer and the
corresponding overheating of the mounted LED. A solution based on the analysis was also
proposed, which after its implementation has proved the accuracy of the analysis.
Scientific Session 4
Industrial and Power Electronics
Hall 3 & Virtual room 1, Friday 24 July, 10. 30 - 12.00
Chairpersons: Nikolay HINOV, Dimitar ARNAUDOV
4.1. MODELLING OF INDUCTIVE POWER TRANSFER SYSTEM Dobroslav Dankov, Prodan Prodanov
Abstract – The simulation of IPT converters is linked to the use of an appropriate model of
the system transmitter and receiver coils. Three different simulation models are proposed
depending on the equivalent circuit used. The models have been verified with respect to an existing
IPT system by using LTSPICE. The models have been compared as regards their accuracy and
response time by contrasting the simulation and experimental data.
4.2. APPLYING AN AGING MODELS FOR RELIABILITY ESTIMATION OF SUPERCAPACITORS
Prodan Prodanov, Dobroslav Dankov
Abstract – Supercapacitors can be viewed as energy storage devices. As every component in
electronic circuitry, they can cause failures in electronic equipment and therefore are subject of
reliability study. The main factors influencing supercapacitor reliability are operating temperature,
operating voltage and equivalent series resistance (ESR). Those three performance parameters of
supercapacitors should be embedded in the model for calculating parameters such as failure rates,
mean time to failure and reliability.
4.3. BIDIRECTIONAL SERIES RESONANT DC-DC CONVERTER PERFORMANCE IMPROVEMENT
Angel Lichev, Aleksandar Vuchev
Abstract – Experimental research has been made on a bidirectional series resonant DC-DC
converter, operating at a frequency higher than the resonant one. The control of the conducted
energy is done via both phase shifting and operating frequency variation, simultaneously. In such a
way, a linearization of the converter control characteristic is achieved. The research data has then
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been compared to a solely phase shift control method. Better production efficiency of the convertеr
is an additional asset.
4.4. A REVIEW OF SUPERCAPACITORS AS NEW POWER SOURCES IN HYBRID ENERGY STORAGE SYSTEMS FOR ELECTRIC VEHICLES
Miroslav Andreev
Abstract – Supercapacitors are widely spread nowadays. They are known as ultracapacitors
or electrochemical double layer capacitors i.e., EDLC which are energy storage devices which can
provide high energy specified and efficiency. They are based on a nanotube technology. Their
principal characteristics make them suitable for usage in energy storage systems and the possibility
to be charged/discharged rapidly without loss of efficiency for a lot of cycles, much higher than
electrochemical batteries and also release a huge amount of energy power. Compared to Li-ion
batteries, the supercapacitors have lower power density that’s why they cannot compete with
lithium batteries in terms of energy content - cost for Watt per hour, but they can really compete to
cost per kilowatt and cost per unit and their capacity. Nowadays almost all of pure electric vehicles
are equipped with electrochemical batteries which have a lower energy density compared to a
petrol fuel used in vehicles with combustion engines. The supercapacitor pack can be successfully
used in HESS (battery-supercapacitor system) combining different energy storage technologies with
special control strategy using all the advantages of each energy source for improving and reaching
overall performance. This article summarizes the performance of supercapactiros in terms of
energy density, equivalent series resistance and their optimal usage in the automotive sector. This
paper will introduce, concern, review and provide the main types of supercapacitors, their structure
and their usage in applications for electric vehicles and also state of the art of materials. The paper
also presents a brief review of benefits, features, advantages and disadvantages of hybrid energy
systems based on batteries and supercapacitors.
4.5. RESONANT CONVERTERS FOR LOW POWER WIRELESS ENERGY TRANSFER
Vladimir Dimitrov, Nikolay Nehovski, Nikolay Hinov
Abstract – The papers reviews low power wireless power transfer. Typical applications
involve wireless charging of mobile phones and laptops (under 100W). A typical series resonant
circuit is shown along the required formulas to size the power circuit. A simulation showing the
influence of magnetic coupling and control frequency on the output resonant capacitors voltage is
shown.
4.6. ABILITY TO CONTROL THE TEMPERATURE PROFILE OF SOLDERING USING LOCAL HEAT SCREENS
Valentin Videkov, Valentin Tsenev
Abstract – The present paper presents the results of the study of a method of soldering using
heat shields. The essence of the method consists in placing additional metal screens on the soldered
SMD elements, which change the effective heat mass. Changing the effective mass allows for slower
heating of sensitive elements. In the present study, attention is paid to the influence of the thickness
of the printed circuit board on the change of the temperature profile under the screen. The influence
of the additional heat mass in the screen on the moment of the change of the heat profile is also
considered. In addition to the amount of material added to the screen, the temperature of its phase
conversion also has an effect. The results of using a reflow process with infrared heating are
presented.
4.7. THYRISTOR MODULES FOR ELECTRONIC CONVERTERS INTENDED FOR INCREASED VOLTAGE
Kostadin Milanov
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Abstract – This article describes the design specifics of the control and the voltage
distribution of series connected thyristors and the construction features of integrating into a
medium-voltage power converter. The paper shows the feasibility of the solutions and their
implementation in the designing of a three-phase rectifier working at increased voltage. The results,
construction and implementation of thyristor modules made with series-connected thyristors were
commissioned into a rectifier type BELA HV-6500 / 30A manufactured by R&D center at TU-Sofia,
Scientific Applied Laboratory for Contactless Electrical Appliances "BELA".
4.8. APPROBATION OF A MATHEMATICAL MODEL OF A SPECIALIZED MECHATRONIC SYSTEM
Martin Kambushev, Nayden Chivarov, Assen Marinov, Reneta Dimitrova
Abstract – The article discusses a procedure for studying the adequacy of a nonlinear non-
stationary aerodynamic model. The possibility for balancing and the stability of the balanced model
in the altitude-speed range of operation of the real aircraft has been studied. The purpose of the
report is to determine the range of altitudes and flight speeds in which the behavior of the object
and the model coincide.
4.9. CONTROL OF IMPULSE CONVERTER WITH REVERSE ENERGY TRANSMISSION WITH ACTIVE DRIVER CIRCUIT
Yanka Ivanova, Svetoslav Ivanov, Evgenia Vasileva, Dimitar Nyagolov
Abstract – This article presents the research of an active driver circuit with dv/dt feedback,
included in the control system of a converter with reverse power transmission. A comparative
analysis of the transients in the power circuit when controlling the power transistor with
conventional and active driver is made. The influence of the active driver circuit on the frequency
and attenuation of the resonant processes during the switching of the power transistor has been
researched. Conclusions are made about the power losses, the amplitude values of the voltages and
the electromagnetic radiation of the converter.
4.10. COMPARISON OF AN ACTIVE VOLTAGE BALANCING METODS FOR SUPERCAPACITORS
Krasimir Kishkin,
Abstract – This paper presents a fast charging algorithm for battery bank made of connected in
series supercapacitor cells. This algorithm allows simultaneously charging of all sells up to
preliminary set up maximum voltage. Considering the tolerance in the capacitance of each cell and
that, they are connected in series, we know that when the charging current is equal for all cells, the
voltage across each cells will increase with different rate. In the presented algorithm, the charging
current for each cell is different. The voltages across cells increase simultaneously. This method is
compared to the method that the equalization has higher currents in a short time.
4.11. COMPARISON OF A MULTIPHASE TOPOLOGY FOR CHARGING ENERGY STORAGE ELEMENTS
Dimitar Arnaudov,
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Abstract – The paper presents a study of a multiphase converter for charging stations for electric
vehicles. The converter consists of parallel operating units based on high-frequency resonant
inverters. Simulation models of multiphase converters have been developed. Simulation studies
have been conducted to demonstrate the advantages and disadvantages of these systems. The
impact of the asymmetry of the individual units on the pulsations of the charging current is
investigated, as well as the possibilities for regulating the value of the charging current by
changing the parameters of one or several units. The advantages of a five-phase converter over six-
phase one at the same power output are shown.
Scientific Session 5
Instrumentation and Measurement
Hall 3 & Virtual room 1, Friday 24 July, 12.30 - 14.00
Chairpersons: Marin MARINOV, Zhivko KOKOLANSKI
5.1. DYNAMIC ERROR APPRAISAL OF THE PRIMARY TRANSDUCER IN THE SENSOR STRUCTURE OF THE PHYSICAL QUANTITY –
Leonty Samoilov, Darya Denisenko, Nikolay Prokopenko
Abstract – In many cases, the primary transducer (PT) of a physical quantity sensor converts
(normalizes) a variable physical quantity into an electrical signal. The dynamic error of the PT is
determined by the delay time in the PT and the first derivative of the signal. In this article, the
amplitude-frequency response (AFR), of the PT was approximated by the frequency response of the
Butterworth filter. The use of application programs made it possible to obtain numerical estimates
of the delay time in the PT. For the case of the unlimited spectrum under consideration, the first
derivative of the PT signal does not differ from the value obtained using the Bernstein inequality.
The final calculations showed a significant effect of the dynamic error on the total error of the PT.
5.2. DETECTION OF DIFFERENT BEARING FAULTS IN A PERMANENT MAGNET SYNCHRONOUS MOTOR USING PWT AND LVQNN
Hamed Ahani and Vahid Izadi
Abstract – This paper deals with the detection of bearing-related faults in permanent magnet
synchronous motors. First, the motor current was sampled and analyzed using multi-level packet
waveform transformation and then based on different features from the transformed signals, which
resulting from the primary waveform, the LVQ neural network is trained for doing the
classification. The outer-ring, inner-ring, cage, lubricant loss, and imperfect ball fault classes are
considered in this paper. The proposed approach for fault detection shows high accuracy for
practical cases.
5.3. STUDY OF THE AUDIO CHARACTERISTICS OF MOBILE PHONES IN THE CONTEXT OF TRANSMISSION OF BIOMEDICAL SIGNALS CONVERTED
INTO SOUND
Ivo Iliev, Borislav Ganev, Ivan Kanev
Abstract – The remote patient monitoring system has become a research hotspot in recent
years. Using ICT and some wearable technology, it is possible to monitor the user’s health
condition in real-time. At the same time, the development of communication technologies with
higher density of the communication channels is associated with increasingly occurring collisions.
One simple approach using mobile phone (GSM) for patient’s data transmission of audio
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transformed biological signals is discussed in this paper. The results of performed experimental
laboratory tests for determining the acoustic characteristics of GSM devices are presented.
5.4.
5.5. PERFORMANCE EVALUATION OF MEMS PRESSURE SENSORS Borislav Ganev, Dimitar Nikolov , Marin Marinov
Abstract – Atmospheric pressure sensors are important for a number of applications,
including indoor positioning, environmental monitoring and more. This article presents a study of
the main characteristics of micromechanical atmospheric sensors. Four different models of
micromechanical pressure sensors were studied. Some of the models measure along with the
pressure additional parameters, such as temperature, relative humidity and air quality. The
research evaluated the accuracy of the sensors, the influence of the change of basic atmospheric
parameters on it and their noise characteristics. The results show that low-budget micromechanical
pressure sensors offer a number of advantages for efficient implementation of a number of
applications. An important prerequisite for this is the use of appropriate algorithms for fusion of
sensor data, which can increase the reliability of their data.
5.6. CHARACTERIZATION OF DIELECTRIC ANISOTROPY OF REINFORCED SUBSTRATES AT DIFFERENT TEMPERATURES
Plamen Dankov, Valda Levcheva and Mario Iliev
Abstract – The paper considers the temperature behavior of dielectric parameters (dielectric
constant and dielectric loss tangent) of reinforced substrates used in the microwave electronics at
different temperatures. A method has been developed for the determination of the temperature
dependencies of substrate uni-axial anisotropy (different dielectric parameters at different
directions – parallel and perpendicular to the substrate surface). Such information for the
temperature changes of the uniaxial anisotropy of several reinforced substrates has been presented
for the first time.
5.7. THE IMPACT OF THE SYNCHRONIZATION BETWEEN INFRARED CAMERA AND EXCITATION SOURCE ON DEFECTS DETECTION QUALITY
IN LOCK-IN THERMOGRAPHY MEASUREMENTS
Borislav Bonev
Abstract – The aim of this article is to consider the influence of the synchronization between
the excitation source and the thermographic camera on the post-processing results (amplitude and
phase contrast) in lock-in thermography. A simulation study of one-dimensional thermographic
signal models was performed. An electronic module has been developed, allowing changing the
phase of the frame capturing signal. The study was performed using a prepared experimental
specimen. The results for a different phase of the frame capturing signal are presented.
5.8. COMPUTATION OF GEOMETRIC CHARACTERISTICS FROM THERMAL IMAGES OF CORRODED SURFACE OBJECT
Borislav Bonev, Anna Stoynova and Antonio Shopov
Abstract – The increase in temperature in the structural elements can be due to various
factors. Due to the physical nonlinearity of the building materials, it is not possible to perform a
separate analysis for the stress or deformation, which are directly dependent on the changes in the
geometric characteristics. A method for automatic calculation of the geometric characteristics of
corroded objects using an infrared thermography is presented. The results obtained using this
method are verified and analyzed.
5.9. SIMULATION MODELS DEVELOPMENT FOR BATTERY PARAMETERS ESTIMATION
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Evgeni Malev, Toncho Hristov Papanchev
Abstract – The paper presents an overview of systems which analyze the behavior at the
processes charge and discharge of a battery. A physical and two mathematical systems have been
developed to provide information about the basic and secondary battery parameters. The data can
be stored in an array and from there can determined SOC,SOH, trouble-free operation and other
parameters.
5.10. SERVICE PROTOTYPING BASED ON DIGITAL TWINS FOR VIRTUAL COMMISSIONING SCENARIOS
Michael Grethler, Jivka Ovtcharova, Marin B. Marinov
Abstract – For the multidimensional prototyping of services in Product-Service-Systems a
procedure was developed and enriched with typical scenarios like the virtual commissioning of
machines and industrial plants. For the development, design dimensions, main development
aspects, and prototyping attributes were examined and condensed in a service prototyping matrix.
From this matrix, software and service products were prototypically derived for an IT vendor.
5.11. AN INDUSTRIAL IOT PLATFORM AND ITS APPLICATIONS BASED ON THE NEW GENERATION OF INFORMATION TECHNOLOGY
Jieyang Peng, Michael Grethler, Andreas Kimmig, Marin B. Marinov, Jivka Ovtcharova
Abstract – With the application of a new generation of information technology in the field of
manufacturing and the deep integration of computer technology and manufacturing, industrial
production is developing towards intellectualization and networking. Because the current
production system cannot fully mine the value of industrial data and the existence of information
islands in the production process, this paper introduces an industrial Internet of things (IoT)
platform based on 5G, OPC-UA, and other communication technologies. This paper first analyzes
the basic requirements of the industrial IoT, then introduces the architecture and detailed
information flow of this platform, and finally shows the application of this platform in the PHM
field. On the one hand, this paper shows the application of the industrial Internet of things platform,
on the other hand, it provides a reference for industrial data processing.
Scientific Session 6
Micro and optoelectronics
Hall 3 & Virtual room 1, Friday 24 July, 14.45 - 16.00
Chairpersons: George ANGELOV, Rossen RADONOV
6.1. MODELING FOR THERMOGRAPHIC DETECTION OF SUBSURFACE DEFECTS ABOVE DIFFERENT THICKNESS –
Anna Stoynova
Abstract – The results of study the effect of object thickness on subsurface defects detection by
active thermofraphy are discussed. The results of an experiment to determine the effect of object
thickness on determination of the depth of the defect with active thermographic testing is presented.
A thermography simulation was conducted and experimental data were processed.
6.2. THERMAL DESIGN: BASIC STAGES, PROBLEMS AND SOLUTIONS Nikolay Vakrilov, Nadezhda Kafadarova
Abstract – This article discusses the stages in the development of a project in the field of
thermal design and how to reduce the possible risks in the initial stage of product development for
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thermal engineers. An approach for evaluating the thermal efficiency of three test structures of
printed circuit boards through CFD modelling and simulations of heat transfer processes is
proposed. The thermal regime of a COB LED module with a cooling radiator designed for it is
predicted by CFD simulation. Experimental measurements with a prototype of the COB LED
module are performed, which show good compliance with the results in simulations.
6.3. NUMERICAL THERMAL ANALYSIS OF THE PCB CONSTRUCTION IMPACT
Nikolay Vakrilov, Diana Stoyanova and Nadezhda Kafadarova
Abstract – In this research computer modeling and thermal simulations based on CFD for
quantitative estimation of temperature and diagnostic of critical fields with higher risk of
malfunction in DC-DC converters is presented. The influence of structural and technological
factors on the board is evaluated in the thermal analyzes: the percentage of fillers, the thickness of
the inner copper layers. Thermal analyzes were performed at different ambient temperatures and
extreme heat loads.
6.4. COMSOL MODELING OF GEOMETRICAL INFLUENCE OF SONIC CRYSTAL NOISE BARRIER ATTENUATION
Elitsa Gieva and Ivelina Ruskova
Abstract – In the present article the influence of the change of different parameters of the
geometry of the Sonic Crystals noise barriers on the noise attenuation is described. Results with
different peculiarities of the geometry are compared. Sound crystals, arranged in a different
matrices were examined. The modeling is performed with the COMSOL program..
6.5. FABRICATION OF NANOCOMPOSITE BASED OF COPPER NANOWIRES AND SILICONЕ RUBBER
Tobiya Karagyozov, Boriana Tzaneva and Valentin Videkov,
Abstract –In this work the influence of the diluent amount and the method of introduction of
copper nanowires on silicone for preparation of nanocomposite material was investigated. Toluene
(T) added to fresh silicone liquid (S) in S:T proportions from 1:1 to 1:4 was used as a diluent. The
fragmentation of separate nanowires and their distribution in silicone matrix was examined by
optical microscopy. The optimal technological conditions for maximum dispersion and
homogeneous mixing have been established.
6.6. SILICON HALL-EFFECT MULTISENSOR Siya Lozanova and Chavdar Roumenin
Abstract – A novel in-plane sensitive Hall-effect multisensor is presented, in the active
transducer region of which, two Hall voltages are generated independently. This is achieved by the
original design and by the supply formed by two constant currents. The residual offset drift is about
140 times smaller than the drift of a single Hall device. The magnetosensitivity reaches
SRI≈170V/АТ. The signal-to-noise ratio is increased, the measured minimal magnetic induction is
Bmin≈9µT. The characteristics will have impact on quantum communication, and medicine.
6.7. EXTERNAL MAGNETIC FIELD INFLUENCE ON THE ELECTRICAL AND MICROWAVE PROPERTIES ON COMPOSITE MATERIALS,
COMPRISING MAGNETITE AND BARIUM AND STRONTIUM
HEXAFERRITES FILLERS
Kamelia Ruskova
Abstract – The influence of the constant magnetic field on the microwave and electrical
properties of elastomer-based (nitrile butadiene and chloroprene rubber) composites, comprising
magnetite and hard magnetic fillers – strontium and Ba- substituted hexaferrites was investigated.
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It was established that the magnetic modification increases both the electrical conductivity and
electromagnetic wave absorption. The effect observed is due to presence of polar bonds into the
rubber matrix and is connected to the conductive phase of secondary particles structure formation
and structural homogeneity as a result of the external magnetic field impact.
6.8. STUDY ON THE INFLUENE OF THE EXTERNAL MAGNETIC FIELD ON THE PROPERTIES OF THE ELASTOMERIC COMPOSITES BASED ON
BARIUM AND STRONTIUM HEXAFERRITES
Kamelia ruskova
Abstract – The aim of this study is to investigate the structural changes between absorptive-
active fillers and rubber matrix in composite materials as a result of magnetic field impact. As
absorption-active filler was used isotropic magnetite filler and as anisotropic fillers: barium and
strontium-substituted hexaferrites with high field of intrinsic magnetic anisotropy. As a base for a
matrix were used different elastomeric materials. Exploring of the structural changes and
organization of the filler particles and rubber matrix was done under magnetic field impact. It is
obvious from the obtained optical microscopy data. The magnetic field was used during the film
formation with 1800Oe for 24-48h. The obtained composite materials with different ferromagnetic
fillers can be use for microwave absorbers for specific area of shielding applications..
Scientific Session 7
Education and Learning Technologies
Hall 3 & Virtual room 1, Friday 24 July, 16.15 - 17.30
Chairpersons: Ivailo PANDIEV, Katya ASPARUHOVA
7.1. SIMULATION AND EXPERIMENTAL RESEARCH STRATEGY FOR DACS WITH PROTEUS AND OPEN SOURCE PLATFORMS –
Daniela Shehova, Slavi Lubomirov, Katya Asparuhova
Abstract – Modern digital information processing systems represent a challenge when it is
necessary to choose the circuits and devices in the digital channel and it is that which is the subject
of Digital to Analog Converters (DACs) and the devices that work with them. The study described
in the article is aimed at offering software and hardware solutions to study modern DACs and their
applications.
Simulation schemes for testing the parameters and characteristics of DAC through
simulation analysis in the Proteus environment have been designed and tested.
Laboratory modules have been developed using open source platforms to verify the
simulation results that have been obtained.
The proposed strategy for teaching DACs provides new opportunities for knowledge
organization and new ways of teaching and learning aimed at achieving higher quality of the
learning outcomes in engineering education.
7.2. RESEARCH AND TEACHING OF LINE CODING USING ORCAD AND EMONA INSTRUMENTS TRAINER IN ENGINEERING EDUCATION
Angel Chekicev, Daniela Shehova, Slavi Lyubomirov, Stanislav Asenov and Katya
Asparuhova
Abstract – The article discusses the use of the OrCad environment and the Emona Telecoms-
Training Lab ETT-101 for the research and teaching of Line coding in order to help students from
the engineering colleges learn the principles of building digital communication systems. The
simulations developed and presented and the laboratory layout allow examination and comparison
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of the advantages and disadvantages of NRZ-B coding, RZ and RZ-B coding, and AMI coding. The
results of the simulation and experimental tests are presented too.
7.3. TEACHING METHODOLOGY FOR ALL DIGITAL PHASE LOCKED LOOP
Dimiter Badarov and Georgy Mihov
Abstract – This article discusses the methodology, the tasks, the material base and the
problems in the teaching process of all digital phase locked loop. Different types of phase and
phase-frequency detectors are examined. Their parameters are compared and the advantages and
disadvantages for different applications are discussed. Different types of digital integrators and
digital filters are developed and tested along with the different phase-frequency detectors. Different
circuits for Digitally Controlled Oscillator are developed and tested. Several different phase locked
loops are built and tested. Their parameters are compared and discussed.
7.4.
7.5. INTERACTIVE TEACHING METHODS USED IN THE COURSE DIGITAL ELECTRONICS
Adriana Borodzhieva, Ivanka Tsvetkova, Iordan Stoev, Snezhinka Zaharieva
Abstract – One way students to learn faster and for longer time is to learn by doing and
playing. The paper presents interactive methods used for improving knowledge that students will
get while implementing different circuits of latches and flip-flops and their testing on the laboratory
board developed at the University of Ruse in the course Digital Electronics..
7.6. DESIGN AND IMPLEMENTATION OF A SYSTEM FOR MONITORING AND CONTROL OF THE DRYING PROCESS AS A LEARNING OPPORTUNITY
REMOTELY
Nikolay Valov, Irena Valova
Abstract – There are some courses in engineering that cannot demonstrate the overall
production processes. Mathematical models of their most important parts are used in their teaching
so that students can gain an idea of their management and control. This article describes an idea
for a comprehensive follow-up of the process of drying fruits or vegetables. This is a relatively long
process, it can take more than a day. Students can set a selected automatic control and during the
drying process to monitor various output parameters and change others (input) remotely from their
laptops, computers or mobile devices.
7.7. OPERATIONAL AMPLIFIER OPEN LOOP GAIN SIMULATION IN ELECTRONICS ENGINEERING EDUCATION
Dimitar Tokmakov, Stanislav Asenov
Abstract – Simulating the open loop gain of an amplifier circuit is a highly misunderstood
subject in Electrical and Electronics Engineering. In order to address that, we describe four
methods that we use to successfully simulate operational amplifier open loop gain in engineering
education environment.
7.8. APPLICATION OF DIFFERENTIATED INSTRUCTION APPROACH IN COMPUTER SYSTEMS EDUCATION
Atanas Kostadinov, Krassimir Kolev⸸
Abstract – Sometimes there is a difference in student’s level of knowledge about university
course topics. The lecturer should present material to all participants instead of their background.
We have selected differentiated instruction approach to cope with mentioned problem. This method
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has been used in Reconfigurable Logic, VLSI Design as well as Computer Modeling subjects.
Obtained results show that all students benefit from this approach.
7.9. TEACHING SIGNALS AND SYSTEMS VIA GENERAL PUBLIC LICENSE SOFTWARE DURING THE COVID-19 LOCKDOWN
Yuliyan Velchev, Kalin Dimitrov, Lubomir Laskov
Abstract – The work is focused on options for using the functionality of a GNU General
Public License free software. This license guarantee end users the freedom to study at home during
the lockdown. We focus our efforts for using GNU Octave. This software is a high-level
programming language, primarily intended for numerical computations. Octave is suitable for
illustrating of basic linear and nonlinear problems that occurs in telecommunications and are
studied in course Signals and systems. It is a good alternative of mostly used commercial software.
Specific features have been considered in designing of exercise. The methodology of exercise for
students is described.
7.10. STUDY THE IMPACT OF THE NEGATIVE FEEDBACKS ON THE CHARACTERISTICS OF THE AMPLIFIERS
Ivo Dochev, Stoycho Manev, Lilyana Docheva
Abstract – Education in the area of the analogue circuits design is based on deep knowledge
from the electrical engineering, circuits and systems and other scientific disciplines. One of the
main features of the education today is to make this process more attractive. By means of advanced
software products the design of certain analogue electronic circuit can be made easy to understand
for the great majority of the students.
7.11. DEVELOPMENT OF SINGLE-TRANSISTOR AMPLIFIERS MODULAR LABORATORY KITS FOR ELECTRONIC ENGINEERING EDUCATION
Ivailo Pandiev, Eltimir Stoimenov
Abstract – Transistor amplifiers laboratory kits have been developed and implemented for
electronic engineering education. Each of the two laboratory kits contains two single-stage
amplifier circuits that are constructed using discrete components. Objects of study are the AC
behavior of the two basic amplifier configurations with single BJT and MOSFET. In particular, for
development of the kits on separate printed circuit board common-emitter (CE) amplifier common-
source (CS) amplifier, common-collector (CC) or grounded collector amplifier and common drain
(CD) or grounded-drain amplifier are implemented. The modularity concept introduced in this
laboratory kits allows the student to perform an additional task by configuring the electronic
systems to change the operating point of the transistors or change the depth of negative feedback
and load type (active or active-capacitive). The proposed laboratory kits are intended for second-
year students on the Bachelor degree program of “Electronics” at the Technical University of
Sofia.
7.12. DISTANCE LEARNING AND REMOTE LABORATORY EXERCISES ON
POWER SUPPLY SYSTEMS
Dimitar Arnaudov, Ekaterina Otsetova-Dudin
Abstract – The article presents the results of training with remote laboratory exercises on power
supply systems. Problems with the assimilation of the study material and the operation of the
devices during remote laboratory exercises are discussed. It gave us specific points from a
methodological point of view that should be taken into account in this type of training.
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FORUM “ELECTRONICA”
Virtual room 2, 23-24 July 2020.
Presentation of the Project “Optimal design and management of electrical
energy storage systems”, КП-06-H37/25/18.12.2019, Bulgarian National
Scientific Fund.
https://technicaluniversitysofia.my.webex.com/technicaluniversitysofia.my/j.php?MTID=mc471fd11fc32437f39120530da15af0f
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INFORMATION
ELECTRONICA 2020 is technically Co-Sponsored by IEEE.
(IEEE Conference record # 50406)
The accepted and presented papers will be published in the conference Proceeding on
CD and submitted to IEEE Xplore Digital Library, Scopus database.
ДНТ
Address for correspondence
Address:
CEEC (Union of electronics, electrical engineering and telecommunications),
1000 Sofia, 108 Rakovski Str.
Phones:
+359 2 987 97 67
e-mail:
electronica.ceec@gmail.com
ceec@mail.bg
Web site:
http://ceec.fnts.bg
http://e-university.tu-sofia.bg/e-conf/?konf=28
http://ceec.fnts.bg/http://e-university.tu-sofia.bg/e-conf/?konf=28