April 2020, Volume 20, Number 1

Summary:
Tamás BAGI
COMMONLY USED GROUND WIRE OF DISTRIBUTION NETWORKS UNDER VARIOUS OPERATING AND LOAD CONDITIONS [full paper]

Climate change is increasingly leading to extreme weather conditions that threaten the secure operation of high-voltage transmission and distribution networks. In recent years, significant damage and danger have been caused by icing of wires and damage or collapse of tower structures. Damage to the grid threatens the security of electricity supply. It is therefore appropriate to examine the appropriateness of the elements of the electricity network to the changed circumstances. Countries apply different methods to prevent the icing of phase conductors. In high voltage DC networks (e.g. in Russia and China) the de-icing of specified network sections can be accomplished with a simple solution, applying heating power. This method is not applicable in Hungary because we do not have HVDC network. For heating of phase conductors, a new method (the Dynamic Line Rating (DLR) method), based on changing the transmission capacity at HVAC networks, has been recently developed. However, I was not dealing with these methods because they are irrelevant to the de-icing of the ground wires of HVAC networks. Since there was no current flowing in the ground wires during normal operation and each tower is grounded, a new inductive warming method had to be developed. In this paper, I address the electrical and thermodynamic issues of this new method. In this article I mainly deal with the investigation of the ACSR type ground wire with 95/55 mm2 cross section, but the method can also be applied to phase conductors. During the investigations, the electrical parameters were determined by the LABVIEW software and the thermal calculations were carried out by Ansys Workbench software.


Alena POZDÍLKOVÁ - Jaroslav MAREK - Marie NEDVĚDOVÁ
MONITORING OF APARTMENT PRICES IN THE CZECH REPUBLIC THROUGH PARSING A WEB ADVERTISING SERVERS [full paper]

Time series of apartment prices in the Czech Republic are available only in the partial statistics of the Statistical Office. Apartment prices are presented mainly in the articles and comments from the real estate agents. Data unavailability leads to a small number of statistically oriented publications on the real estate market. The main aim of our paper is thus to introduce a software solution for parsing real estate websites. Of course, we are only able to retrieve data on demanded prices from advertisements, actual prices are not achieved. By automatic polling, we are able to get data on the floor area of advertised apartments and the asked purchase price. A Python script was written to retrieve data from sreality.cz. The MongoDB database is used to store ads. New ads are saved directly to the database. Then, daily average apartment price of 1 square meter for each municipality are calculated. The filtered data can then be displayed or exported to a file via the web interface. In the statistical analyses, we present graphs showing the development of apartment prices and the number of advertisements in various municipalities of the Czech Republic in the period of 09/2018 – 12/2019. Next, we address the issue of clustering of municipalities with regard to the similarity of relative price changes.


Habib BENBOUHENNI - Abdelkader BELAIDI - Zinelaabidine BOUDJEM
POWER RIPPLE REDUCTION OF DPC DFIG DRIVE USING ANN CONTROLLER [full paper]

Over the past years, many kinds of control strategies is proposed for doubly fed induction generators drives. Among them, direct power control (DPC) has gained more importance due to simple control structures and fast dynamic response. However, it has a disadvantage of high ripples in active power, reactive power, and slow response because of hysteresis controllers in active and reactive. To improve the performance of DPC and to reduce the active and reactive powers ripples, DPC based artificial neural network (ANN) controller is proposed in this work. The simulation is carried out using Matlab/Simulink and compares the proportional-integral (PI) controller and in DTC artificial neural is implemented and simulated results are shown.


Sihem BOURI - Abdelhalim BENMANSOUR
OPTIMIZATION OF THE TRANSPORT NETWORK STRUCTURE BY THE ANT COLONY METHOD
[full paper]

The optimization of the network structure amounts to structuring an optimal configuration among several by modeling it with a graph that admits nodes and edges. The determination of the optimal graph is to determine the optimal connection of the system by which its conventional cost is minimal. This article discusses the optimization of the transport network structure using ant colony method.


František SILVÁŠI - Martin TOMÁŠEK
EXTENDING LEAN CELLULAR AUTOMATA FRAMEWORK – BOUNDARY CONDITIONS AND PROPERTIES OF CANONICAL FORMS [full paper]

We present several extensions to our Lean–based formal mechanized framework for computing with cellular automata (CA). First we extend the definition of CAs to allow for specification of arbitrary boundary conditions. We use this addition to represent constant and periodic boundaries. We then formulate and prove numerous missing properties pertaining to canonical forms of cellular automata, culminating in a theorem stating that canonical forms preserve counts of nonempty cell states.


Patrik PERHÁČ - Slavomír ŠIMOŇÁK
ALGORITHMS AND DATA STRUCTURE LIBRARIES FOR JAVA [full paper]

This paper is dedicated to the comparison of different libraries of algorithms and data structures for the Java language. Within the paper currently available and relevant libraries are analyzed and compared. Selected libraries are compared in terms of provided implementations of the particular data structures and algorithms, but also based on the performance of these implementations. Then a summary of the results and recommendations regarding the practical uses of each library are provided. Performance is measured using the Java Microbenchmark Harness. According to the results of this paper, implementations in Java Collections Framework are suitable for most use cases, when more complex data structures are not needed. When more specific data structures or algorithms are needed, that are not covered in Java Collections, GUAVA is a good alternative. For graph-like data structures the use of libraries JUNG and JGraphT is recommended.


 

Publisher

    Faculty of Electrical Engineering and Informatics, Technical University of Košice, Slovak Republic

    Reg. No.: EV 2921/09,
    thematic group B1,
    ISSN 1335-8243
    The editorial board assumes no responsibility for damages suffered due to use of acts, methods, products, instructions for use or other ideas published by the article authors whatsoever.
EAN 9771335824005