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The errors between the design parameters and experiment data of the power transformer in idle mode can reach 15-20% or more, because engineering techniques do not take into account in full all factors. Therefore, the aim of the work is to develop improved circuit models, which are interconnected with spatial electromagnetic field models. These models consider the active part design of the transformer, the hysteresis of the nonlinear magnetic properties of electrical steel, asymmetry and non-sinusoidal phase-to-phase currents and provide high accuracy determination of rated idling parameters of transformer. To research the idle mode of transformer, the circuit models were conjugated with 3D and 2D magnetic field models. Their numerical implementation was carried out by means of finite element method on the example of a three-phase power transformer (10 kVA, 380/220 V). The reduction of the computational time was performed by doubling cancellation of the volume of 3D three-phase transformer domain and the conformal transition to the 2D geometric domain. Determination of the effective magnetic characteristics of electrical steel according to single-phase idling experiment data, allows to take into account the combined effect of hysteresis and eddy currents, design and technological factors on the specific losses and magnetization power. This ensures high accuracy of the description of the interrelation between magnetic flux density and magnetic field strength, reducing of current error and relative errors in the calculation of idling losses up to 1.41% and 1.2% for the 3D model and up to 5.18% and 3.2% for the 2D model.

Today, the significant volumes of network traffic circulate through the Internet. The sources of such traffic are, in particular, the diverse territory distributed “smart” devices. The number of named devices is about billions. As a consequence, the relevance of bringing to practice the core concepts of the Internet of Things paradigm is constantly becoming more and more topical. It’s bound with the problem of granting the interoperability between the components of distributed software systems, built over the aforementioned devices. The web services are typically considered as the components of the system. To this end, to establish the interoperability between the components, despite the standardization, the need for the development of effective tools and techniques, granting the interoperability between the web services, arises. The goal of the work is to increase the effectiveness of the Internet of Things system engineering process by way of checking the interoperability between the components during the designing. The goal is achieved through the development of formal model for checking the interoperability between the components of the Internet of Things system by way of model checking in an automated manner. The novelty of proposed solution is grounded on the usage of Temporal Logic of Actions, corresponding formalism and the concept of action as the basis for compact and easily reconfigurable formal specifications synthesis. The adequacy of proposed model has been proved through the case study. The verification-related time costs have been estimated.

The purpose of this work is to develop a diagram version of the compensating device, and its control strategies using a phase-shifting transformer device. The purpose has been achieved performing a complex of research based on structural-simulation models both for the compensating device as a whole, and for the phase-shifting transformer. Based on the phase-shifting transformer model, calculation experiments in idle, short-circuit and under load conditions have been carried out. The obtained data allowed to determine the energy characteristics of the object of research and to perform analysis of its characteristics during the process of adjusting the angle of phase shift. The paper also provides the results of research in the regime's parameters issue of the device as a whole. The obtained data confirmed the functionality of the proposed reactive power source. The novelty of the work consists in the development of innovative circuit variant of controlled compensating device. Its component parts are susceptances, allowing carrying out a symmetrical adjustment of reactive power both consumed and offered to the network in a predetermined range. A control diagram for adjusting windings of a phase-shifting transformer has been proposed. The control's principle of power electronic keys provides control of the phase shift of the voltage at the output terminals of the device in the range from 0° to 60° at 15 switching positions. The proposed technical solution provides symmetrical smooth control of reactive power in a wide range at the point of connection of the device to the network.

The object of the study is a frequency converter based on IPC technology. The purpose of the study is to determine the device's performance characteristics by means of a mathematical apparatus describing the area of existence of operating modes for active and reactive power. On the basis of combinatorial laws, variants of non-repeating states of thyristor keys were obtained. The initial phases of active and reactive power components are determined by varying in accordance with the cosine law with two non-repeating combinations of key switching on each pair of conjugate reactive elements. The input of two constants made it possible to simplify the arguments influencing the magnitude and direction of the transmitted power by the device. A comparative analysis of the regime parameters and the characteristics obtained with the help of the simulation model and calculated by the proposed method confirms the identity of the results. The error of the method fluctuates between 0.5% and 1.5%. The developed method made it possible to determine a number of unique variants of the transmitted power level when adjusting the angle \(\delta_{sr}\) in the range from 0º \(\div\)360º . This allows to adjust the magnitude and direction of the transmitted power when "sliding" or slow and arbitrary frequency changes. Thus, the proposed method made it possible to determine with a high degree of accuracy the domain of existence of the regime parameters with the construction of switching diagrams of keys to maintain an ordered unidirectional power flow with frequency matching by the device under study.

Wrocław ; Prace Naukowe Uniwersytetu Ekonomicznego we Wrocławiu = Research Papers of Wrocław University of Economics, 2013, Nr 324, s. 126-135

Purpose of this work is in the development and modification of control scheme and of basic algorithms of discontinuous space-vector modulation for synchronous and balanced regulation of multi-inverter topology of six-phase open-end winding installation with four insulated dc sources. This purpose has been achieved due to including in the control and modulation scheme of specialized control correlations connecting coefficients of modulation of inverters, required power ratio between dclinks, and voltages of the corresponding dc sources. So, basic novelty of this research is in the fact, that the elaborated and investigated control and modulation algorithms for installation on the base of inverters with discontinuous space-vector modulation (with both 300 -non-switching intervals and 600 - non-switching intervals) insure both required power sharing capability between dc links and advanced harmonic composition (without even harmonics and subharmonics) of spectra of the phase and line voltages of six-phase installation. Mutual comparison of behavior of system with two basic schemes of modified discontinuous pulsewidth modulation (PWM) has been executed. Investigation of harmonic composition of the phase voltage of multi-inverter system illustrates an important fact, that for the all analyzed control modes, connected with balanced adjustment of drive under different conditions, phase voltage of installation has symmetry for any control regimes, including control modes with fractional frequency ratios between switching frequency of converters and fundamental frequency of installation, with absence in its spectra of undesirable subharmonics. Factor of minimization of subharmonics in spectra of voltage and current of ac drives of different topologies is especially important for the medium-voltage medium-power installations on the basis of PWM converters.

Our article focuses on the essence, characteristics, and the structure of the labor potential of the region as well as its role in socio-economic development, territorial and environmental characteristics of labor resources and mechanisms for the reproduction of labor potential. Our results are based on a conceptual and methodological review of foreign and domestic sources. Perspective directions of labor resources research manifest such common features as the assessment of migration risks, the influence of globalization factors, forecasting the dependence of labor productivity at the regional level on market factors, climatic conditions, insurance mechanisms, and other factors. We conclude that research activity directed at human resources of the regions and their qualitative and quantitative properties is extremely high. Moreover, we note a high level of interest of scientists to the problem of labor potential at the micro, meso and macro level in Russian Federation. Our paper pays special attention to the analysis of existing approaches to methods for assessing the labor potential of the region, as proposed by Russian researchers and applied in the Russian Federation. Moreover, it considers the features of the main methodological approaches, studies their classification, as well as the technology of evaluation depending on the research tasks and objectives. We describe the method used for measuring the labor potential of a region on the basis of the index method which allows us to take into account its specific conditions of its reproduction and use at the regional level, as well as to conduct reasonable comparative assessments. In addition, we present our own calculations carried out on the basis of the proposed method and employing the state and the level of development of labor potential in the North Caucasus and Southern Caucasus federal districts, as well as in the Russian Federation as a whole.

Sustainable economic development is also determined by the availability of primary energy supply. Geographical incoherence of energy production and consumption areas leads to new challenges in providing consumers with energy. The purpose of this work is to analyze and assess trends and problems related to the provision of energy resources, mainly of the natural gas for Republic of Moldova in the context of new challenges in the natural gas market and rhe changes in their transport infrastructure. The investigative methodology is based on the analysis of time series of production, consumption and import of energy resources at global and regional level in 1990-2017. It is proposed to using the linear approximation functions. The coefficients and the its signs of these functions ("plus" or "minus") and the value of and the determination coefficient are used for the quantitative analysis of the production, consumption and import trends of primary energy and natural gas. Europe and Asia ensure their energy balance by massive energy imports. The Southeast European region, including the Republic of Moldova, imports large sums of primary energy resources. The need to import natural gas in the Romania-Moldova-Ukraine sub-zone is currently estimated at about 12 million tons of oil equivalent. The new energy corridors for the transportation of natural gas will lead to new challenges regarding the natural gas supply of the Republic of Moldova. Information on possible scenarios of natural gas supply to the Republic of Molodova is presented and the estimated costs for natural gas transport for these scenarios are presented.