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  Problemele energeticii regionale

E-Journal №1-2(41)2019

"PROBLEMS of the REGIONAL ENERGETICS (special issue)"


1 Mathematical Modeling of New Algorithms for Single-Phase Earth Faults Protection in a Compensated Electrical Network
Authors: Syvokobylenko V. F., Lysenko V. A. Donetsk National Technical University Pokrovsk, Ukraine
  Abstract: New algorithms have been developed for selective protection against phase-to-earth faults in power supply systems of 6–35 kV. In such, due to the impact of an arc-suppressing compensat-ing reactor (Petersen coil), the selective action of traditional protection devices is not ensured. The purpose of the work is to develop new algorithms for selective protection against phase-to-earth faults in power supply systems with Petersen coil. Mathematical modeling showed that at frequencies of 200–400 Hz, the Petersen coil practically does not reduce the capacitive current in the damaged junction when the phase is shorted to ground, unlike in the case of fundamental frequency. Therefore, to protection device current and voltage with a frequency of 300 Hz are used. This current and voltage are extracted from the current and voltage of zero-sequence using band-pass frequency filters and are used to determine the direction of reactive power. Scientific novelty comprises determining the direction of reactive power using both the current and voltage after the filters, and also their derivatives, which significantly improves the sensitivity and stabil-ity of the relay; the performance of filters being controlled depending on the instantaneous val-ues of the zero sequence voltage amplitude, which ensures the stability of the filters; the im-plementation of a two-channel protection relay for receiving a constant (instead of a pulsating) signal at the output device. The effectiveness of the developed protection is confirmed by the results of the mathematical modeling, tests on a laboratory bench and the supply of full-scale signals registered by the recorders in real networks.
  Keywords: power supply system, compensated power grid, mathematical model, digital filter, phase to earth fault, Petersen coil.
2 Simulation of the Initial Stability of the Floating Dock for the List and Trim Stabilization Tasks
Authors: Kondratenko Y.P.1, Topalov А.M.2, Kozlov O.V.2 1Petro Mohyla Black Sea National University, Mykolaiv, Ukraine 2Admiral Makarov National University of Shipbuilding, Mykolaiv, Ukraine
  Abstract: The aim of this work is the development and study of a mathematical model of the floating dock initial stability for solving problems of list and trim stabilization. The proposed model allows calculating the change of the parameters of the initial stability of the floating dock (with and without a vessel) for different values of the draft. The initial stability of the real floating dock of the middle class with a carrying capacity of 8500 tons is studied using the simulation model de-veloped by the authors in the FREE!SHIP Plus. With the help of this computational model, the operation of immersion of the floating dock is considered. At each stage of immersion at a cer-tain draft, the parameters of the initial stability of the floating dock are calculated, namely, the values: transverse and longitudinal metacentric heights, centers of buoyancy, centers of gravity, and mass displacement. Corrections of transverse and longitudinal metacentric heights due to changes in the mass of liquid in ballast tanks and the influence of its free surface are also taken into account. Based on the obtained modeling results, the following dependences are calculated: a) moments from list and trim angles at different values of draft, b) moments of list and trim from draft at various values of list and trim, c) angles of list and trim from the fill level of the respective tanks. These dependences can be used for further development of the list and trim stabilization system for the given floating dock.
  Keywords: floating dock; initial stability; list; trim; simulation.
3 Diagnostics of Linear Systems in the State Space
Authors: Verlan A. F.1, Polozhaenko S. A.2 1Institute of modeling problems in power engineering named after G. E. Pukhov. Kyiv, Ukraine 2Odessa National Polytechnic University. Odessa, Ukraine
  Abstract: The analysis of the state of the problem of quality ensurance and proper functioning of electri-cal systems and devices was carried out. It showed that not only the complete feasibility of monitoring their performance at the production and operation stages should be considered, but also the potential diagnostics of the systems and devices being developed should be ensured. At the same time, the limitations of the existing methodological support for conducting diag-nostic experiments were noted. It was indicated that a possible solution of this problem was to use for diagnosing at all stages of the life cycle (in particular, designing, manufacturing and operating) the controlled systems and model-oriented methods, which made it possible to fill up a measurement information deficiency during the simulation of their schemes using the ap-propriate models. The purpose of this research was to further develop the model-oriented methods for diagnosis of the technical state of the electrical systems and devices, which was achieved by formalizing the task and developing constructive algorithms for localization of faulty subsystems in the state space. In this context, a method for the diagnostics of the linear systems (devices) was proposed, which ensures testing of the working hypotheses by describ-ing them (the essence is the representation of the model) in the state space. Unlike the existing ones, the method allowed us, when conducting a diagnostic experiment, to avoid measuring the potentials at the nodes of the selected (localized) subcircuits. The application possibilities of the method in the engineering practice were illustrated by examples.
  Keywords: diagnosis, method of diagnosis, health hypothesis, model, localization of a faulty subcircuit.
4 Research of the Finite State Machine with Programmable Logic as a Part of Digital Information and Control System Based on FPGA
Authors: Barkalov A.1, Titarenko L.1-2, Zeleneva I.3, Hrushko S.3 1University of Zielona Gora, Zielona Gora, Poland 2Kharkiv National University of Radio Electronics, Kharkiv, Ukraine 3Zaporizhzhya National Technical University, Zaporizhzhya, Ukraine
  Abstract: The purpose of this research is to determine the effective way of implementation of the control algorithm, as an important functional part of information and control computer systems. The search criterion is the minimum of internal hardware FPGA resources required for the control unit implementation. This criterion allows miniaturization of dimensions, improves reliability by reducing the number of interconnections inside the chip, and ensures the possibility of a compact arrangement of various system components, which is especially important when using the “system-on-chip” design technology. The control unit holds a prominent place in the digital information and control systems. A comparative analysis of two control unit models represented as a finite state machine with either hard or programmable logic was proposed. Advantages and disadvantages of both models were determined according to the peculiarities of the information and control system algorithms, and, it was proved that the FSM model with a programmable logic matched these peculiarities in a greater degree. The purpose of this study was achieved due to the application of the proposed method for the implementation of the FSM with the programmable logic using the embedded memory of the FPGA and ProASIC chips. The main result was a substantial decrease in the LUT number used. The experimental results were obtained applying the chips of the world's top manufacturers - Xilinx, Altera/Intel, Microsemi. The studies were carried out based on the onboard computing complex control algorithm.
  Keywords: control algorithm, digital information and control system, FSM with programmable logic, FPGA, embedded memory.
5 Fractional Integral-Differentiating Control in Speed Loop of Switched Reluctance Motor
Authors: Busher V. V., Horoshko V. V. Odessa National Polytechnic University Odessa, Ukraine
  Abstract: This paper deals with the feedback speed control of a switched reluctance motor using the fractional-order controller. Due to the polar-pole construction and pulsed power windings, at which saturation of the magnetic system occurs, standard PI or PID controllers based on motor description with differential equations of integer order have led to significant errors and inaccuracies in the dynamic and static modes. The purpose of the work is optimization of dynamic and static modes using fractional integral proportional controllers. The goal was achieved by solving the problem of identifying a switched reluctance motor based on the fractional order differential equations with a power of 0.7, parameters found by genetic algorithms. It allowed taking into account the nonlinear dependences of the magnetic flux and torque so that the object behaved like a linear one. Then it became possible to synthesize controllers with a fractional order of integration and differentiation based on standard methods of the theory of the automatic control. It was shown that the parameters of the model changed with voltage regulation. The behavior of a closed system was compared when tuning the speed loop to the technical optimum and fractional order of astaticism , taking into account such changes in the control object. Significance of the results consisted in the fact that the fractional order controllers using a motor model based on a fractional-order differential equation ensured a high quality system (the minimum of the first matching time, the overshoot was no more than 2%), unattainable with classical PID controllers.
  Keywords: switched reluctance motor, fraction calculus, controller with fraction order, parameter identification, fractional astatism, genetic algorithm.
6 Numerical-Field Calculation of the Angle Torque Characteristic of the Three-Phase Inductor of the Magnetic Field of the Electromagnetic Stirrer in Processing Dissimilar Mixtures
Authors: Milykh V.I., Shilkova L.V. National Technical University «Kharkiv Polytechnic Institute» Kharkov, Ukraine
  Abstract: The evaluation of the possibility of using electromagnetic stirrers for dissimilar mixtures in vari-ous technological processes requires the study of their work under load conditions. The load mode of the agitator is ensured by the needle ferromagnetic elements moving inside a cylindrical working chamber under the influence of a rotating magnetic field, whose effectiveness can be predicted by analyzing the magnitude and nature of changes at the electromagnetic moment. The magnetic field ensures ordering of the ferromagnetic elements, therefore the magnetic permea-bility in it along the longitudinal and transverse axes becomes different. Due to the anisotropy of the magnetic properties of the composite medium in the working chamber, strong influences arise on this medium, based on the magnetic tension forces acting on the ferromagnetic ele-ments. The purpose of this work was to present the method of calculation of the electromagnetic moment and determination of its dependence on the angular displacement of the rotating mag-netic field of the inductor. The distribution of the magnetic induction inside the working cham-ber in the idle and load modes was compared, it gave an idea of the distribution of the magnetic field lines in those modes, set out the basic principles for calculation of the angular characteris-tics of the torque of the electromagnetic stirrer. The proposed method was based on the multi-position numerical calculations of the magnetic fields in the FEMM software package. Compara-tive calculations of the angular characteristics of the torque were performed at different magnet-ic permeabilities of the composite medium in the working chamber.
  Keywords: electromagnetic stirrer, inductor, magnetic field, numerical-field calculations, electromagnetic moment, angular characteristic, magnetic permeability, anisotropy.
7 Control System Structure of the 4th Drive Power Installations for Electric Vehicles
Authors: Osadchyy V.V., Nazarova E.S., Brylistyy V.V. Zaporizhzhia National Technical University Zaporizhzhia, Ukraine
  Abstract: The main global trend in the automotive industry is a significant increase in the share of hybrid and electric vehicles in total production, as well as the expansion of the related infrastructure. One of the main objectives of the development of an electric vehicle was to increase mileage without recharging and to improve the handling and maneuverability, as well as the passengers’ safety and cargo transportation conditions. The increase in mileage can be achieved both by improving the battery, and by improving the energy efficiency of the electric drive. The passenger safety is largely dependent on the vehicle handling. Therefore, an urgent task is to improve the performance and energy efficiency of the electric vehicles using the electric drive. The aim of this work was to justify the use of the 4-drive installation, which allowed us to redistribute the torque between the drive wheels, as a base for a modern electric vehicle. The redistribution of the moment between the drive wheels by means of an automated electric drive improved the controllability and safety of the vehicle by maintaining the torque of the drive wheels at the maximum possible level under the given driving conditions. Namely, they are the vehicle speed, angle of rotation and coefficient of adhesion of the drive wheels to the road surface. Using this method enabled to improve the energy efficiency compared to the mechanical method of the redistribution of the moment by eliminating the braking losses of the wheels, which required a reduction in the moment.
  Keywords: automobile industry, automobile production, electric car, automatic control system, torque, electric drive, four-wheel drive, 4 engines.
8 The Improvement of Energy Harvesting Efficiency of Constant Current Source
Authors: V. V. Martynyuk, V. D. Kosenkov, and M. V. Fedula Khmelnytskyi National University Khmelnytskyi, Ukraine
  Abstract: This study aims at determination the maximum power point parameters for the constant current source with nonlinear parasitic elements. The aim has been achieved by analyzing the differential resistance and equivalent parameters of a circuit with a constant current source. As a result, the buck-boost converter circuit is considered with the equivalent current source, which is formed with a photovoltaic module. The problem of the maximum photovoltaic module of energy harvesting is related to the research of its nonlinearity, which determines operating points at the current-voltage curves under different irradiances and temperatures. Thus, the differential resistance of photovoltaic module is examined to determine the parameters of the maximum power point mode. The main result of the research is the model, which differs from the known models by the description of the dependence between the buck-boost converter duty cycle and input equivalent current source parameters in the maximum power point mode. The results of modelling are supported by experimental research of the laboratory layout. The presented circuit ensures the operating point close to the maximum power point of the solar panel equivalent current source. The duty cycle of the buck-boost converter is determined directly from the equivalent current source model with the parameters estimated analytically from the irradiance and temperature of the solar cells. The presented approach allows developing the maximum power point tracking algorithms based on the estimation of the equivalent current source parameters that provide improvement of the energy harvesting efficiency.
  Keywords: current source, energy losses, nonlinearity, solar panel, DC-DC converter, differential resistance.
9 The Method for Reducing the Term Vector Size for Category Classification of Text Documents
Authors: Golub T.V., Tiahunova M. Yu. Zaporozhye National Technical University Zaporozhye, Ukraine
  Abstract: The article proposes a method for reducing time necessary for subsuming a certain document in order to classify the text documents by reducing the term vector size of certain categories. Ac-cording to the method, the term weight factors were calculated for each classification category to implement subsuming process at the stage of training a certain system. As a result of the analysis of the obtained data, the individual category terms, whose weight values did not exceed the ex-perimentally determined threshold value, were excluded from the term vector of the category by equating them to zero. Those terms were not involved in the further subsuming process at the testing stage. As the input data for the experimental part, the TF-SLF reference method and its modernization CTFSLF according to those described above were proposed. Due to the applica-tion of the method proposed, the differential term vector size for each category was decreased. Despite the increase in the compile time of the term vector according to categories, which was performed only once, the calculation time used to determine whether or not a document be-longed to a specific category decreased without losing the classification quality. In addition, due to the fact that the proposed method excluded the words that were used in the texts frequently, it became possible to exclude the stage of removing the stop words from the pretreatment process of the analyzed text. For the same reason, the problem of misprints and the words "stuck togeth-er" in the initial, training sample was solved.
  Keywords: text classification, stemming, terms vector, term weight, TF-SLF.
10 Analysis of Technical and Energy Indicators of a Multi-Motor Electric Drive for Urban Public Transport
Authors: Voytenko V.A., Vodichev V.A., Kalinin A.G. Odessa National Polytechnic University Odessa, Ukraine
  Abstract: The aim of this article was to analyze the profitability of using a multi-motor electric drive in-stead of a single-motor electric drive in a city vehicle to ensure the reduction of the electrical energy losses. To achieve the goal a mathematical model was used to calculate the energy losses in the single-motor and multi-motor electric drives of a bus with a different number of traction induction motors. The calculation was carried out for the steady-state driving modes with differ-ent speeds and transient acceleration modes. The change in the load torque of the vehicle's mo-tors due to the change in the rolling friction force of the wheels with a different number of pas-sengers carried was taken into account. The novelty of the work is that the use of a multi-motor electric drive shown for the first time allowed the reduction in the energy losses in the traction induction electric motors when the vehicle is moving at a constant speed and during acceleration with a different number of passengers carried. Moreover, to obtain energy saving, the number of motors used in a multi-motor electric drive should vary depending on the speed and accelera-tion, as well as on the total load torque of the multi-motor drive. The formula was obtained ana-lytically for the calculation of the number of motors of a multi-motor electric drive, which would ensure energy saving compared to a single-motor electric vehicle.
  Keywords: induction motor, vehicle, power, energy loss, single-motor and multi-motor drive, voltage frequency, voltage amplitude.
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