December 2002, Volume 2, Number 4
DYRCZ, K. P. — ORLOWSKAKOWALSKA, T. Influence of Kalman Filter Parameters to the Induction Motor Speed Estimation 
STOIMENOV, L. — STOJANOVIĆ, D. An Active, ObjectOriented MediatorBased Framework for the Development of Gis Applications 
DŽMURA,
J. — MARTON, K. Vplyv merného elektrického odporu popolčeka na účinnosť vysokonapäťového odlučovača 
BORBEĽ,
M. — ŽILKOVÁ, J. — TIMKO, J. Neural Speed Estimator for the Induction Motor Drive 
CIMBALA,
R. MultiStress Ageing and Its Influence on Electrical Strength 
JADLOVSKÁ,
A. Neural Networks Based Predictive Control of NonLinear System 
HYNEK,
J. Proč genetické algoritmy selhávají? 
BENÍK,
Š. — HAJACH, P. Štrukturovaná cylindrická anténna sústav 
NOVITZKÁ,
V. About Metamathematics of Computer Programming 
MEŠTER, M. — CHLADNÝ, V. A New Approach to Power System Transient Stability Assessment 
RUSNÁK, J. Innovative Technologies for Voltage and Power Flow Control 
Summary: 
Krzysztof P. DYRCZ  Teresa ORLOWSKAKOWALSKA Influence of Kalman Filter Parameters to the Induction Motor Speed Estimation [full paper] The paper deals with the application of Kalman filter for state variable estimation of the induction motor. The mathematical model of the extended Kalman filter used for rotor flux and speed estimation was presented. Some simulation results were shown in the paper. The influence of parameters of the induction motor equivalent circuit on the state variable estimation quality was demonstrated. The problem of suitable choice of Kalman filter parameters, such as elements of the covariance matrix Q, was also discussed. The possibility of practical realisation of such Kalman filter was discussed.

Leonid STOIMENOV  Dragan STOJANOVIĆ An Active, ObjectOriented MediatorBased Framework for the Development of Gis Applications [full paper] Most current geographic information systems assume and present the static world. But, new generations of GIS applications have much more demands in comparison to possibilities, which could provide traditional database management systems. Information that exists in the spatial database may be updated over time. Also, the very important demand is time capability to answer to state changing in database.

Jaroslav DäMURA  Karol MARTON Vplyv merného elektrického odporu popolčeka na účinnosť vysokonapäťového odlučovača [full paper] This paper deals with the influence of dust electrical resistivity on the electrostatic precipitator activity. Electrical resistivity is one of the critical parameters influencing fly ash collection by electrostatic precipitator. The electrical resistivity of fly ash depends on the chemical composition of the ash, the components of flue gases, and the temperature. Fly ash composition is largely determined by the type and composition of the coal being burned, and the furnace operating conditions. Precipitators work best, when the dust has a resistivity of between 102 and 1010 Wm. At lower resistivities the dust tends to fall off collecting electrodes and becomes reentrained in the gas. At higher resistivities backionization becomes a problem.

Martin BORBEĽ  Jaroslava ŽILKOVÁ  Jaroslav TIMKO Neural Speed Estimator for the Induction Motor Drive [full paper] Artificial neural networks are recently showing good promise for application in power electronics and motion control system. They have been applied mainly in control of converters and drives. Sensorless control of the induction motor drives requires knowledge of the instantaneous value of the rotor speed. Various methods of the rotor speed estimation were recently used, based on the mathematical models of the induction machine, on nonlinear phenomena of the motor and based on neural networks. This paper deals with utilisation of artificial neural networks (ANN) for observing an induction motor drive variables. The observing is realised utilising several quasisingle estimators, number of those is equal to number of observed variables. The observers are based on feedforward neural network and on cascadeforward backpropagation ANN, respectively. The structure of the neural network is analogues to the mathematical model of an induction motor. Stator currents and stator voltages of the induction motor are inputs of the neural network. Estimation is based on offline learning principle using backpropagation algorithm with LevenbergMarquardt algorithm. The simulation using Matlab with Simulink realises the application results. Rotor flux, torque and angular speed of an induction motor are estimated. Changes in the rotor resistor do not influence the quality of observing.

Roman CIMBALA MultiStress Ageing and Its Influence on Electrical Strength [full paper] The purpose of this article is to show how electrical and thermal field exercise an influence on lifetime of insulation material. Fist of all simple ageing is described. When thermal stress is analyses, the Arrhenius’s law is used together with chemical kinetic reaction theory. From theses assumption thermal classes of each material applied in insulation system can be determined. Nowadays there is material with class F. It is ReMica material based on mica, epoxy resin and textile base. After thermal heating it is prepared for industry used. It is necessary to know the influence of temperature during production and service, because ageing mechanism can be change if certain boundary above thermal class is overcame. The same situation is during electrical stress. For thermoplastic materials the sufficient theory isn’t present nowadays, especially for critical limits. Finally the combination of both brings their interaction. The influence from single stresses can’t be cumulated without correction.

Anna JADLOVSKÁ Neural Networks Based Predictive Control of NonLinear System [full paper] In this paper nonlinear dynamical system is controlled using a predictive control strategy. This control technique needs a model of the system, which can predict the output of the system. The nonlinear identification can be done using neural feed forward model as a predictor. The predictive control strategy is based on the online optimisation of a cost function. The online minimization is done using LevenbergMarguardt algorithm by simulation language MATLAB.

Josef HYNEK Proč genetické algoritmy selhávají? [full paper] Genetic algorithms are quite often presented as a panacea that is suitable to almost any problem and is going to replace traditional techniques. They are oversimplified, oversold and their real potential is very often overestimated. In order to avoid some mistakes related to genetic algorithms application and to prevent frustration associated with that it is necessary as in the other fields of human activities to learn from faults that were done before. To be able to do it these failures must be recorded, described, and analysed.

Štefan BENÍK  Peter HAJACH Štrukturovaná cylindrická anténna sústava [full paper] Often goal interference and wittingly obstruction are antenna systems use in radar technology alternatively in communication systems. A expedient on solving problems incident with activity interferences and unwanted signals is applique adaptive antenna systems. Specific facilities this systems are used on safekeeping of radars and communication systems from interference, when a tendency of approach interference isn't noted in advance. Antenna array is important component of adaptive antenna system. It realizes a lot ofchannel middle of receipts of signals. On achievement spatial selectivity is needs implement receipts of signals with antenna system, which is composite from two alternatively several spatial arrangement elements. For area adaptive antenna systems are used prefer linear antenna systems and singular plane antenna systems in period. For many applications in smart technology is needed to design antenna system with much good directional alternatively omnidirectional properties. Appropriate procedure what is used on achievement directional alternatively omnidirectional facilities is to configure individual antenna elements from those is created antenna array into various geometrical structures.

Valerie NOVITZKÁ About Metamathematics of Computer Programming [full paper] How to cancel the software crisis? To prove that programs are reliable. But it is possible only in mathematics. So, the programming has to use mathematics. In this paper we present basic mathematical concepts that enable to start discussion about the theory of programming in the framework of the classical mathematical logic, an axiomatic set theory, category theory, and universal algebra.

Mariin MEŠTER  Vladimír CHLADNÝ A New Approach to Power System Transient Stability Assessment [full paper] In this article is presented a simple method for transient stability assessment of a single machineinfinite bus power system using catastrophe theory. Catastrophe theory is a mathematical technique for the qualitative analysis of system equations, defining the jump phenomena and sudden changes caused by smooth alterations in the situation.

Jozef RUSNÁK Innovative Technologies for Voltage and Power Flow Control [full paper] Developments in semiconductors drive power electronic into transmission and distribution applications as solution of power flow control and voltage stability problems. Advances in power semiconductor technology and power electronic equipment have provided a means for fast and smooth control of three system parameters that have a direct impact on power flow: the bus voltage, the line impedance and the transmission angle [8]. This paper describes new means of power electronic concrete FACTS (Flexible Alternating Current Transmission Systems) devices. These devices can fulfil functions of reactive shunt compensation, series compensation, phase shifting, series voltage injection device and shunt current injection device or a combination of these. This article describes individual FACTS devices and their application for voltage and power flow control.
