ISSN 1805-3386

April 6, 2020


2013 No.1

Heat Pumps Earth-Water

Zach, P., Hradílek, Z.

The article deals with heating of large properties using heat pumps of earth-water type. An example of use of geothermal energy can be seen in the heating systems installed in the Assembly Hall of VSB - Technical University Ostrava. The source of heat comprises 10 heat pumps connected within cascade pattern with the total installed capacity of 700 kW. The primary source of energy for heat pumps is formed by the set of 100 boreholes to the depth of 140 m.


Keywords: Heat pumps, geothermal energy


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Solar Energy as a Primary Source of Energy for a Cloud Server

Priščáková, Z., Rábová, I.

Cloud Computing is a modern innovative technology for solution of a problem with data storage, data processing, company infrastructure building and so on. Many companies worry over the changes by the implementation of this solution because these changes could have a negative impact on the company, or, in the case of establishment of a new companies, this worry results from an unfamiliar environment. The aim of this paper is to offer and scientifically confirm a proposal of an accessibility solution of cloud by implementing of solar energy as a primary source.


Keywords: Cloud Computing, data accessibility, solar energy


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Control Techniques of Grid Connected PWM Rectifiers under Unbalanced Input Voltage Conditions

Bejvl, M., Šimek, P., Škramlík, J., Valouch, V.

Current-controlled voltage source converters are widely used in grid-connected applications, for example for ac drives with indirect frequency converters. The structure and parameters of the PLL are developed and proposed in order to cope with the grid containing both the positive and the negative sequence components, and minimize the wrong frequency transients during phase angle steps and also in the start-up stage. The DSC (Delayed Signal Cancellation) technique was realised. There is also necessary to compensate the negative sequence component in the grid voltage. The negative sequence component of the grid voltage causes ripples of the dc voltage in the DC link. Several sophisticated topologies of converter current controller were developed, simulated and tested for this purpose. Results of simulation and experimental tests are provided to evaluate different current control schemas and phase locked loop techniques.


Keywords: Phase Locked Loop (PLL), DSC, Current Controller, PWM rectifier


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Flickermeter Comparison Test

Bilik, P., Petvaldsky, P., Kaspirek, M.

The paper describes the test of flicker evaluation made by eleven different types of power quality analyzers. The standard IEC 61000-4-15Ed.2 (Functional and design specification of flickermeter) issued on August 2010 specifies performance testing. Existing flickermeters from different manufacturers may provide different results when processing non-uniform voltage fluctuations. The flickermeters response to voltage varying signals with envelope shape typical for sawmill, heat pump, granulator was tested. Voltage fluctuation caused by operating of this electrical equipment was measured in the real low voltage distribution network by means of the power quality analyzer Topas 1000. One-period records of voltage fluctuation were available for the analysis. These were simulated on the programmable power voltage source HP6834B in the university lab.


Keywords: Flicker, power quality analyzer, flickermeter, voltage fluctuation


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Utilising of EMTP ATP for Modelling of Decentralized Power Sources Connection

Medveď, D.

The ensuring of the quality of electric power is one of the actual tasks that could be solved in the field of electric power supplying. For that reason it is necessary to monitor the particular electric quantities, such as voltage and current fluctuations, overvoltages, voltage drops, voltage harmonic distortion, asymmetry phase voltages, frequency variation and fluctuation and others that cause e.g. power losses, devices failure, and so on.

This article deals with some typical failures in a power system that unfavourably cause considerable electric losses or undesirable damages. The prevention of potential failure leads to decreasing of power losses. It is possible to solve the various power networks using computer modelling. One of the suitable computer software is the Electromagnetic Transient Program (EMTP ATP). This software is mostly intended for solving and modelling transient phenomena and this feature was also utilized during the modelling. In this software there were modelled various connections of decentralized power sources and determined the maximum power and node voltage that can be connected in particular part of the power grid. In this article there are also indicated another various failures that caused significant power losses (short-circuits, overvoltages caused by connection and disconnection of a part of the grid, atmospheric overvoltages).


Keywords: power system, computer modelling, EMTP ATP, decentralized sources, SimPowerSystem, electric losses


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Use of Specialized Devices to Power Flow Control in Power Systems

Beňa, Ľ., Jakubčák, R., Kolcun, M.

This article discusses specialized devices for the power flow control in power systems. Today it is an actual topic because of permanent increasing power flow in the transmission lines. This trend can lead to overloading of transmission lines and can endanger the security of electric energy supply.


Keywords: power flow control, FACTS, phase shift transformer


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