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  Problemele energeticii regionale

E-Journal №2(28)2015



1 Possible Operation Modes of Moldovan, Ukrainian and Romanian Electrical Power Systems Joint Work
Authors: V. Postolati, E. Bykova, V. Berzan, V. Boshneaga, V. Suslov, T. Radilov Institute of Power Engineering of the Academy of Sciences of Moldova Chisinau, Republic of Moldova
  Abstract: Types of intersystem controlled tie-lines, that may allow the joint work of power systems of Moldova, Ukraine and Romania, are proposed in this paper. The use of intersystem controlled ac transmission lines based on compact one-circuit overhead transmission lines (OHTL) and two-circuit controlled self-compensated OHTL (CSCTL) with phase-shifting transformers on the other hand is also stated. Two types of phase-shifting transformers are considered: the first one – with bounded range of phase angle control between the voltage vectors’ system at the output with respect to the other at the input; the second one – with circular rotation of one voltage vectors’ system with respect to the other. The first type of devices is aimed to control the power flows within the system or through the intersystem tie-lines of synchronously operating systems. The second type of phase-shifting transformers is aimed to interconnect power systems that operate non-synchronously and to control the power flows between them through connecting OHTL. The first type of devices was introduced in calculation model in 330 kV Moldavskaya GRES – Chisinau OHTL and the second one – in the OHTL that are connecting the power systems of Moldova and Romania. The dependences of power flows through power system’s and intersystems’ OHTL are established on base of performed calculations, research and analysis.
  Keywords: compact one-circuit and two-circuit controlled self-compensated overhead transmission lines, phase-shifting transformers.
2 Electromagnetic field calculation for 110 kV power line
Authors: Berzan V., Patsyuk V., Ribacova G., Ermuratschii V. Institute of Power Engineering of the Academy of Sciences of Moldova Chisinau, Republic of Moldova
  Abstract: The paper studies the evolution of values for the characteristic electric field and magnetic field generated by power line voltages and currents voltage 110 kV their value based snapshots. These evolutions we examined in changing the value of the angle of the voltage vector and current vector within 0o...180o. The conductors are placed horizontally and triangle tops with different lengths of the sides. The electric field distribution was calculated with finite volume method. Since the electric field distributions were determined parameter values of LEA110 kV. The values of the line parameters, which were determined by the finite volume method, difference from the values calculated by the traditional method. In this context finite volume method presents attractive enough to determine the parameters of power lines and spatial distribution of the electric field in three-phase lines.
  Keywords: electric field, method of finite volumes, electric line parameters.
3 Application brushless machines with combine excitation for a hybrid car and an electric car
Authors: Gandzha S.A., Kiessh I.E. South Ural State University Chelyabinsk, Russian Federation
  Abstract: This article shows advantages of application the brushless machines with combined excitation (excitation from permanent magnets and excitation winding) for the hybrid car and the electric car. This type of electric machine is compared with a typical brushless motor and an induction motor. The main advantage is the decrease of the dimensions of electric machine and the reduction of the price for an electronic control system. It is shown the design and the principle of operation of the electric machine. The machine was modeled using Solidworks program for creating design and Maxwell program for the magnetic field analysis. The result of tests is shown as well.
  Keywords: brushless electric machine, combined excitation, permanent magnet, excitation coil, magnetic flow control.
4 Zero-voltage and Zero-current-switching of Half-bridge PWM Converter for High Power Applications
Authors: Berzan V., Ermurachi Iu. Institute of Power Engineering of the Academy of Sciences of Moldova Chisinau, Republic of Moldova
  Abstract: The design and control of a half-bridge converter that ensures zero voltage and zero current shifting of electronic switches throughout the load band for a large range of input voltage is described in this paper. The new proposed topology of the converter achieves a substantial reduction of losses due to the shifting of electronic switches and oscillating currents. The proposed topology has a simple technical scheme with minimal number of control elements with a total low price, as well. The control of the proposed converter can be implemented by applying the technique of pulse width modulation (PWM). The functionality, stability and performance of the proposed converter topology have been verified on an experimental converter at power range 420 W (400V, 50V).
  Keywords: half bridge (HB) converter, pulse width modulation (PWM), zero voltage switching (ZVS) zero current switching (ZCS).
5 Electric Drive Discrete Control System with Automatic Switching-On Reserve for Autonomous Settlement
Authors: Tsytovich L.I., Brylina O.G., Nesterov A.S., Tyugaev A.V., Loginova N.A., Lopukhova E.A. South Ural State University Chelyabinsk, Russian Federation
  Abstract: The paper aims at developing of control the water supply system’s electric drives for autonomous settlement. The system provides automatic switching to a reserve control channel at refusal of any of the functional elements of the working regulation channel. Usually, such systems have a test signal generator and analyzer to system response to their impact. This result to an increase in the structural redundancy of the system, increase its cost and increase the requirements for the staff qualification. A specific feature of the system is its ability to self-diagnosis of catastrophic malfunctions of scheme’s components and an automatic switching-on the reserve control channels, without applying any test signals to the whole complex of electrical equipment. Multi-zone integrating regulator with frequency-pulse-width modulation realizes this technical solution. Control system structure and signals timing diagrams are presented. The construction principle of adaptive interval-code synchronization device with improved noise stability to control the voltage regulators serving for smooth start-up of asynchronous motors of water pumps is considered as well. Such solution allowing increase noise stability and reliability work of the system in conditions of limited power electrical networks, which is characteristic for the autonomous settlements. The article may be of interest to specialists in the field of power electronics and information electronics, electric drives and process automation.
  Keywords: integrator, relay element, voltage regulator, multi-zone integrating regulator, thyristor, diode, adder, synchronization device, autonomous settlement.
6 Investigation of Asymmetrical Modes of Three-Phase Three Leg Combined Transformer-Phase-Shifter
Authors: Bosneaga V.A., Suslov V.M. Power Engineering Institute of Moldova Academy of Sciences
  Abstract: On the base of previously proposed model of three-phase three leg transformer windings connection scheme for combined transformer-phase shifter was made, for which calculations and analysis of specific characteristics of different steady state asymmetric modes were performed. At this the electromagnetic coupling of the windings, located on different legs of transformer core was taken into account. As the base 10 kV transformer was used, and different short circuits, combined with phase failures at feeding source were investigated. For the considered regimes vectorial diagrams for windings currents, voltages and relative values of magnetic fluxes in the legs and zero sequence magnetic flux, flows out of magnetic circuit, were constructed, giving clear idea about their particular features.
  Keywords: asymmetric modes, three legs magnetic circuit, short-circuits and phase failures, combined transformer-phase-shifter, zero sequence magnetic flux.
8 Multifunctional Heat Pump Installation for Dairy Plants
Authors: Sit M.L., Sit B.M. Institute of Power Engineering of the ASM Chisinau, Republic of Moldova
  Abstract: The article presents the installation based on the approach using the integration of the carbon dioxide heat pump in pasteurization and cooling installation for milk and in installations for preparing of hot and "icy" water. The scheme differs from the prototype by the use of additional heat exchangers and of their connection to the main elements of the installation. A proposed technique of elements connection in the heat pump installation permits to compensate the effect of temperature of cold water supply source, which is low-grade heat source for the heat pump, on the quality the work of the installation. The design of the installation enables to compensate the impact of seasonal variation of water temperature. The installation ensures the COP = 5.3.
  Keywords: heat pump, pasteurization and cooling of milk, carbon dioxide, thermodynamic cycle.
9 Numeric Simulation of Heat Transfer from a Single Round Tube Shielded with Wire Mesh
Authors: Dymo B.V., Pastuhov S.Y., Chegryntsev V.F., Anastasenko S.N. Admiral Makarov National University of Shipbuilding Mykolaiv, Ukraine
  Abstract: This paper presents the results of development and investigation of heat transfer at transverse flow of round tube with wire screen using the software ANSYS Fluent 3D-model. Selection of optimal parameters of the finite element model, in particular, transition shear stress transport model as well and boundary conditions are realized. Instructed and combined net is used at numerical calculations. This net is built with the help of generators grid-torus ANSYS CFX Mesh 14.0. The problem of verification of conformity of the numerical model of the heat transfer of a single screen-covered round tubes according to physical experiment for the same tubes in the range of Reynolds numbers Re = (5000...35000) was studied. We established that discrepancy between physical experiments and numerical simulation results not exceeds 5% with respect to the data of physical experiment.
  Keywords: heat transfer, tubes, wire screens, drag coefficient, numerical simulation.
Authors: Denysova Alla, Bodnar Igor, Denysova Anastasiia Educational and Research Institute of Institute for Energy and Computer Integrated Control Systems Odessa National Polytechnic University Odessa, Ukraine
  Abstract: One of the basic directions of perfection of heat supply systems is the tendency of transition to the low-temperature heating systems based on application of heat pump installations. We consider heat supply system with heat pump installations using subsoil waters. Numerical simulation of thermal processes in the elements of a single-stage and double-stage heat pump systems has been worked out. Values of depths of wells and their quantity, necessary for effective operation of the offered installations, and values of capacity of electric water pumps for subsoil waters unit are calculated. Capacity of compressor electric drive and coefficient of performance of heat pump for the conditions of the city of Odessa are presented.
  Keywords: heat pump installation, subsoil water, utilization, low potential energy, single-stage heat pump, double-stage heat pump, coefficient of heat transformation, efficiency.
11 Solar Multi-stage Refrigeration Systems on the Basis of Absorber with the Internal Evaporative Cooling
Authors: Doroshenko A.V., Kirillov V.H., Antonova A.R., Liudnicky K.V. Educational and Research Institute of Refrigeration, Сriotehnology and Eco-Energetics Odessa National Academy of Food Technologies, Ukraine
  Abstract: In the article, the developed schematics are presented for the alternative refrigeration systems and air-conditioning systems, based on the use of absorbing cycle and solar energy for the regeneration of absorbent solution. Multi-stage principle of construction of drying and cool contours of solar systems is used with growth of concentration of absorbent on the stages of cooler. An absorber with internal evaporative cooling, allowing to remove the separate evaporated cooler, usually included after the absorber of the proper stage, is developed. Heat-mass-transfer apparatus of film-type, entering in the complement of drying and cool contours compatible and executed on the basis of multichannel compositions from polymeric materials. The preliminary comparative analysis of possibilities of the solar refrigeration systems and air-conditioning systems is executed.
  Keywords: solar systems, drying of air, heat-mass-transfer apparatus, film flow, absorption, desorption, evaporative cooling.
12 Efficiency Growth of Combined-cycle Cogeneration Plant with the Heat Supply System
Authors: Denysova Alla, Mazurenko A.S., Denysova Anastasiia Odessa National Polytechnic University Odessa, Ukraine
  Abstract: Energy efficiency of modern technologies of the combined production of heat and electricity and ways of energy saving on base of recycling secondary energy sources has been estimated. It is shown that the most effective for cogeneration are combined-cycle plants. The rational scheme of interaction of combined-cycle cogeneration plant with heat supply system has been offered. Theoretical bases of interaction of main installation with a contour of heat and hot water supply system has been developed. Numerical modeling of temperature parameters and the analysis of results of numerical modeling has been executed. The technology of increase of energy efficiency of installations on base of recycling heat is offered. Increase of effectiveness of system is achieved due to full use of heat and reduction of losses to environment. It is established, that the rational scheme of interaction of combined-cycle cogeneration plant with heat supply system allows increasing energy efficiency on 2 % that corresponds to economy of fuel 3 %.
  Keywords: combined-cycle plant, cogeneration, heat supply system, efficiency, energy saving
14 The Development of Modern Technologies – Is the Basis of a Sustainable Economy?
Authors: Andronaty N. R. Institute of Power Engineering of Academy of Sciences of Moldova Chisinau, Republic of Moldova
  Abstract: The significance of the problem of providing technological assurance of processes is demonstrated based on examination of the development of computer technology in Moldova. Only human potential availability of well trained professionals, logistics and coordination of the whole process of the work cycle from research to production can provide a high level of quality, contribute to promoting and ensuring market competitiveness of manufactured products. It is demonstrated that there are many areas that require the use of computer systems, including analog and digital specialized electronic machines. Providing conditions for the evolution of new technologies and their development is the most important prerequisite for sustainable economic development.
  Keywords: technology, computer science, competitiveness, sustainable economy
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