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ELECTROENERGETICS
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Controlled Compact High Voltage Power Lines
Authors: Postolati V., Bycova Е., Suslov V. Institute of Power Engineering of the Academy of Sciences of Moldova Republic of Moldova Timashova L., Shakarian Yu., Kareva S. Research and Development Center at Federal Grid Company of United Energy System, Joint-stock company Russia
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Abstract: Nowadays modern overhead transmission lines (OHL) constructions having several significant differences from conventional ones are being used in power grids more and more widely. Implementation of compact overhead lines equipped with FACTS devices, including phase angle regulator settings (compact controlled OHL), appears to be one of the most effective ways of power grid development. Compact controlled AC HV OHL represent a new generation of power transmission lines embodying recent advanced achievements in design solutions, including towers and insulation, together with interconnection schemes and control systems. Results of comprehensive research and development in relation to 110–500kV compact controlled power transmission lines together with theoretical basis, substantiation, and methodological approaches to their practical application are presented in the present paper. |
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Keywords: compact controlled OHL, transmission capacity, phase control.
DOI: https://doi.org/10.5281/zenodo.1208395
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Inverter for Installations with Intermittent Electricity Production
Authors: Ermuraki Iu., Berzan V. Institute of Power Engineering of the Academy of Sciences of Moldova Chisinau, Republic of Moldova
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Abstract: A new architecture of the inverter used in the convertion of electric energy generated by renewable energy sources is studied in this paper. The distinctive features of this inverter is the special block which compensates pulsing of the current with double frequency, characteristic for these inverters. The switching of electronic keys is realized using the method TCM In this block, like in the inverter, which assures the switching at the voltages near to zero (ZVC). The proposed algorithm of controlling the electronic keys permits to increase the work frequency up to hundreds of kHz. Electronic keys operate at variable frequency, which changes during the work cycle both slowly and by jump. The assurance of admissible heat regime is performed using forced cooling air flux and by convection. The increase of releasing process of the heat is assured by original construction of radiators which forms the turbulent mode of cooling air flux. These changes of the architecture of the inverter have allowed the minimization of mass, sizes and price indicators. It has been manufactured a functional laboratory sample with output power of 2kW the voltage of direct current of 450V or 48 V and output alternating voltage of 230V, with sizes 175mmX35mmX30mm. |
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Keywords: energy source, intermittent, converter, half bridge, high power density, inverter, triangular current mode (TCM), zero voltage switch (ZVS).
DOI: https://doi.org/10.5281/zenodo.1208391
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Modified Two-core Phase-shifting Transformer Based on the Classical «Delta Connection» Scheme
Authors: Golub I.V., Zaitsev D.A., Zubareva I.G. Institute of Power Engineering of the Academy of Sciences of Moldova Chisinau, Republic of Moldova
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Abstract: Nowadays, in joined power systems increases the role and significance of phase-shifting devices, which are used in the quality of FACTS-controllers (Flexible Alternative Current Transmission System), allowing solving various problems of modes management in a complex-closed inhomogeneous network. A modified version of the two-transformer circuit phase-adjusting device, built based on the classical single-transformer scheme «Delta Connection» has been studied in the paper. The proposed device’s topology differs from the classical of single-transformer one so that the control coil is supplied by a lower voltage than phase level, which in turn makes it possible to use it in high rated voltage networks. A mathematical model of the device, which describes the change of parameters of operation mode of phase-shifting transformer under the adjusting of the phase-shifting angle, has been provided. The achieved results can be used for comparative analysis when determining the technical and economic efficiency in the deal of further development of phase rotating devices of transformer type. |
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Keywords: phase-shifting transformer, phase shift angle, a complex conversion factor, the calculated power of the device.
DOI: https://doi.org/10.5281/zenodo.1208375
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Energy Quality in Microgrids
Authors: Golovanov Nicolae University Politehnica of Bucharest Bucharest, Romania
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Abstract: Measures for limiting environmental pollution by power plants using fossil fuel sources and for efficient use of local energy sources can cause significant changes in the structure of the electricity distribution networks through the development of micro-grids that can operate practically isolated or connected to the public electricity network, which ensures bilateral exchanges of energy.
The microgrid requires a detailed analysis of the level of quality of electricity supplied to the microgrid. The detailed analysis of technical solutions is needed to ensure a necessary level of electric energy quality in practically isolated microgrid. Some of the specific conditions of microgrid operation are analyzed, which will ensure operation of the system at the action of disturbances.
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Keywords: electric energy quality, microgrid, electromagnetic perturbations.
DOI: https://doi.org/10.5281/zenodo.1208361
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Contribution of FACTS to the Electric Energy Quality in Distribution Systems
Authors: Chaki Oana Energy Systems Department, Faculty of Energetics, University Politehnica Bucharest, Romania
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Abstract: Limitation of electromagnetic disturbances occurring in industrial processes and improving power quality are major concerns of professionals in the energy sector. The goal of the work consists in emphasizing the power quality problems incurred due to equipment, which causes disturbances in electricity distribution networks, and highlightes solutions for their effective functioning. The paper presents an application using specialized software to analyze power grids in order to create an overview of solutions for efficient operation of the distribution system in case when a user determines fluctuations of electrical supply voltage. The work aims verifying the connection of a STATCOM to limit disturbances, the data will be validated by experimental tests. |
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Keywords: flicker, electromagnetic perturbations, STATCOM.
DOI: https://doi.org/10.5281/zenodo.1208373
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Reactor-Capaсitor Device for Flexible Link Between Non-Synchronous Power Systems
Authors: Bosneaga V., Suslov V., Postolaty V. Institute of Power Engineering of the Academy of Sciences of Moldova, Kisinau, Republic of Moldova
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Abstract: In present flexible interconnections for transmission of required active power between different power systems is used, as a rule, so-called DC back-to-back link. The aim of this work is the investigation of proposed reactor-capacitor device for flexible connection of asynchronously alternating current power systems with the same nominal values of frequencies for parallel operation. The reactor-capacitor device was elaborated. The installation develops the idea of controlled reactor alternating current link, and provides reactive power balance in the unit and needed value of the output voltage module. The basic characteristics of reactor-capacitor device for controlled power transmission were investigated. Analytical expressions for device elements parameters were derived. These ensure necessary ratio of voltages modules of linked power systems and reactive power balance of the device at circular output voltage vector rotation for a given load admittance. Obtained parameters ensure constant active power flow between linked asynchronously power systems and device reactive power internal balance. |
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Keywords: controlled, flexible connection of AC power systems, combined reactor-capacitor device.
DOI: https://doi.org/10.5281/zenodo.1208399
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Multiplicative Integral Measure of Evaluating the Energy Security Situation
Authors: Fedorchenko S., Fedorchenko G. Pridnestrovian State University Tiraspol, Republic of Moldova
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Abstract: The approach to the evaluation of the integral measure estimation of energy safety with using a generalized utility Harrington-Menchers’s function is considered in this paper. The algorithm of formation of the integral index includes the use of both additive and multiplicative measures. To test data on the energy security were used referred to Transnistria. It is presented an example of the construction of such a measure. During carrying out of this work the analysis of the indicators recommended in the open literature as components of energy safety is made. It is shown that a significant part of these indicators is closely linked with others. |
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Keywords: generalized utility function, galaxy correlation, a display method, energy security.
DOI: https://doi.org/10.5281/zenodo.1208397
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Vulnerability of Energy Consumers - National Security Issue
Authors: Musatescu Virgil National Romanian Centre – World Energy Council Bucharest, Romania
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Abstract: Energy providing is a complex problem, which includes both common features for all categories of consumers and particularities, which emerge from the declaration on human rights. As an index of the level of heat using the concept of 'energy poverty'. In counterbalance, this concept proposes the use of the notion of "vulnerability" for these purposes. The concept of "vulnerable consumer" point of view of energy is still defined in the 2012 electricity law in Romania. In this context, the paper examines the vulnerability characteristics indicating meanings on widening energy paradigm by replacing the phrase "energy poverty" by "energy welfare". The paper presents quantitative issues regarding the current situation in Romania with explaining the need treatment paradigm change simplistic approach to the problem of vulnerable consumers, which really is a matter of national security. |
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Keywords: energetic poverty, vulnerable consumers, paradigm of energy welfare, energy efficiency, national security.
DOI: 10.5281/zenodo.1208381
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HEAT POWER ENGINEERING
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Heat Transfer Modeling of Staggered Bundle with Round Tubes Screened by Mesh
Authors: Dymo B.V., Pastuhov S.Y., Epifanov A.A., Anastasenko S.N. Admiral Makarov National University of Shipbuilding Мykolaiv, Ukraine
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Abstract: The article presents the results of CFD modeling of heat transfer and aerodynamic drag for the first three rows of cross-flowed staggered bundle consisting of round tubes screened by wire mesh. Geometric model of this bundle was developed. Selection of optimal parameters of the bundle finite element model realizes on the base of transition shear stress transport model. Two separate geometric models for even and odd rows of bundle have been elaborated for the scope of computational resources optimization. The results of numerical modeling of heat transfer for the first three rows of the bundle were approximated with the criteria dependences. It has been established that heat transfer stabilization occurs from the second row of the bundle. Stabilized heat transfer is 15 % higher than that for the first row of the bundle and 1.2 … 1.7 times as large in comparison with equivalent bare-tube bundle in a range of Reynolds number from 5000 to 35000. Aerodynamic drag data for the first three rows of the bundle have been obtained. |
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Keywords: heat transfer, bundle of tubes, wire mesh, numerical simulation, heat transfer coefficient, drag coefficient.
DOI: https://doi.org/10.5281/zenodo.1208389
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Calculation of Transient Temperature and Thermal Stresses at Calculus of Heat Transfer Coefficient Considering the Radiation
Authors: Gorbunov A.D., Uklеina S.V. Dneprodzerzhinsk State Technical University Dneprodzerjinsk, Ukraine
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Abstract: The problem of simplifications for solving problems of cooling / heating of bodies under the joint action of convection and radiation is considered. The mathematical formulation of the problem of non-stationary nonlinear heat, allowing along with convection, to take approximately into account the heat radiation. The solution of the problem for a thin body thermal model, based on the substitution method, linearizing the right boundary condition, as well as through the integral equation relationship between heat flow and surface-average and mass – average temperatures for the simple bodies in a regular stage of thermal conductivity. Two engineering methods were developed for calculating the temperature fields and axial thermal stresses during cooling (heating) bodies of simple shape in the form of a plate, ball, and cylinder by convection and radiation in quasi-stationary stage. It is shown that neglecting heat transfer by radiation can lead to significant errors in calculation of the temperatures (up to 26%). The adequacy of the solutions has been tested at extreme cases, in the lack of heat transfer by radiation. |
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Keywords: engineering calculation method, quasi-stationary state, simple shape objects, cooling, heating, convection, radiation, thermally thin object, on-axis thermal stresses.
DOI: https://doi.org/10.5281/zenodo.1208365
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General Problems of Moldovan District Heating Systems
Authors: ¹Chernei M., ²Leu V. ¹StateUniversity of Moldova, ²National Agency for Energy Regulation Chisinau, Republic of Moldova
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Abstract: The paper presents a short description of the evolution of the district heating systems in the Republic of Moldova. It describes the current situation of the district heating systems, reflects economical and technical aspects and problems the thermal energy units confront with. It also examines the development opportunities for the district heating systems in Chisinau and Balti municipalities. Presents conclusions and proposals. |
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Keywords: district heating system, thermal energy unit, municipal heat zoning.
DOI: https://doi.org/10.5281/zenodo.1208385
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Energy Supply System for Industrial Poultry Houses
Authors: 1Sit M.L., 1Juravliov A.A., 2Doroshenko A.V., 2Goncharenko V.A. 1Institute of Power Engineering of the Academy of Sciences of Moldova Chisinau, Republic of Moldova 2Odessa National Academy of Food Technologies, Odessa, Ukraine
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Abstract: The gas engine driven carbon dioxide heat pump designed for providing the heat, cold and electricity for industrial poultry house is proposed. The scheme differs from the known by using recuperative heat exchanger installed between the exhaust air duct of poultry house and heat pump evaporator and the heat curtain installed on the air duct after the evaporator. The air coming into the poultry house after the regenerative heat exchanger is supplied to the heat pump gas cooler. The heat pump produces heat of the required parameters of the input air and water for watering of poultry, space heating, etc. Heat pump compressor is driven by gas engine (GPA), by natural gas or biogas. The part of the gas-piston engine heat is used for adjusting the optimal heat pump mode and for regeneration of the absorbent in an evaporative cooler. The proposed technical solution of the above scheme provides a higher COP of the heat pump. Installing of heat curtain does not require the use of non-freezing solution to prevent icing of the air outlet of heat pump evaporator. The latter allows producing, besides electric power and heat, still cold (with the use off the adsorption-refrigerating machine) and provide drying air inlet evaporative cooler (if necessary). |
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Keywords: heat pump, evaporative cooler, poultry house, gas drive, energy efficiency.
DOI: https://doi.org/10.5281/zenodo.1208381
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The National Services Network EURAXESS As an Efficient Tool For Integration In the European Research Area
Authors: Raboşapca Irina1, Alexandru Rosca2 1 Center for Fundamental and Applied Research Funding, Academy of Sciences of Moldova 2 Center of Political Research and International Relations, Legal and Political Research Institute, National Contact Point for the Marie Skłodowska-Curie actions Republic of Moldova
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Abstract: EURAXESS is a unique initiative of the European Commission, which aims to promote the growth of research careers and stimulate the researcher’s mobility in European area. The initiative was created to protect and develop the European space of research and and to help the scientific community to improve the career and social development. |
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Keywords: EURAXESS, European Commission initiative, researcher’s mobility, European Research and Innovation areal, career, social development.
DOI: 10.5281/zenodo.1208393
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