2023 № 3 Електротехніка і Електромеханіка

Постійне посилання колекціїhttps://repository.kpi.kharkov.ua/handle/KhPI-Press/62918

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Acceleration of exit to steady-state mode when modeling semiconductor converters
(Національний технічний університет "Харківський політехнічний інститут", 2023) Yagup, V. G.; Yagup, K. V.
The purpose of the article is to develop a method and algorithm for the accelerated calculation of steady states of thyristor converters using computer models of converters based on the use of the theory of difference equations in the form of recurrent linear relationships for state variables on the boundaries of the converter periods. Methodology. The article is devoted to the solution of the problem of reducing the cost of computer time to achieve the steady state of the thyristor converter. For this, it is proposed to use difference equations, for which the values of the state variables at the limits of the periods of the converter's operation are taken as variables. These values are accumulated during the initial periods of the transient process of the converter, after which the coefficients of the difference equations are calculated, and the following limit values of the state variables are found using the defined difference equations. A program in the algorithmic language of the MATLAB system is presented, which implements the proposed method and algorithm compatible with the visual model of the converter. Results. The theoretical foundations of the proposed method and the area of its applicability are substantiated. Recommendations are presented for determining the number of periods of the flow process that must be calculated for further implementation of the method. An algorithm for forming matrix relations for determining the coefficients of difference equations with respect to the values of state variables at the boundaries of periods is shown. Matrix equations are given that allow calculating the parameters of the steady state. All stages of the algorithm are illustrated with numerical examples. Originality. The method rationally combines all the advantages of visual modeling based on the numerical integration of equations using the method of state variables for the periods of operation of the converter with the analytical solution of the recurrence relations obtained on this basis for the values of state variables at the boundaries of adjacent periods. Practical value. The proposed method makes it possible to reduce by several orders of magnitude the computer time spent on calculating the parameters of the steady-state mode of the converter and, at the same time, to significantly improve the accuracy of these calculations. The practical application of the method is very effective in research and design of thyristor converters of electrical energy parameters.
Analysis of the thermal state of the electromagnetic mill inductor with oil cooling in stationary operation modes
(Національний технічний університет "Харківський політехнічний інститут", 2023) Milykh, V. I.; Shaida, V. Р.; Yurieva, O. Yu.
An electromagnetic mill (EMM) for the technological processing of various substances, which is based on the stator of a three-phase induction motor, is being studied. The stator winding has an increased current density, so the mill is provided with a system of forced cooling with transformer oil. Problem. Currently, there are no works on the thermal state calculation of the EMM with the given design and oil cooling. Therefore, the study of such EMMs thermal state is relevant, as it will contribute to increasing the reliability and efficiency of their work. Goal. Formation of a mathematical model of the thermal state of the electromagnetic mill inductor and the analysis of its heating in stationary modes of operation with cooling by transformer oil. Methodology. The problem of calculating the thermal state, namely the temperature distribution in the main parts of the electromagnetic mill, is solved by the equivalent thermal resistance circuit method. The design of the EMM is provided in a sufficiently complete volume, and on this basis, a corresponding equivalent thermal replacement circuit is formed, which is supplemented by an equivalent hydraulic circuit of oil passageways. An explanation is provided for the composition and solution of the equations algebraic system that describes the distribution of temperatures by the constituent elements of the EMM. Results. The thermal calculation results of the electromagnetic mill showed that the maximum heating temperature is much lower than the allowable one for the selected insulation class. According to the hydraulic scheme, the necessary oil consumption, its average speed and the corresponding pressure at the inlet of the intake pipe are determined, which are at an acceptable level. It is noted that the rather moderate temperature state of the inductor and the hydraulic parameters of the oil path are facilitated by such innovations in the design of the EMM as the loop double layer short chorded winding and axial ventilation channels in the stator core. Originality. Now EMM thermal equivalent circuits with air cooling only have been presented. Therefore, the developed thermal circuit of the oil-cooled inductor is new and makes it possible to evaluate the operating modes of the EMM. Practical value. The proposed technical solutions can be recommended for practical implementation in other EMMs. Taking into account the identified reserves of the EMM temperature state, a forecast was made regarding the transition from its oil cooling to air cooling. But the use of air cooling requires a change in the design of the EMM.
Application of a wavelet neural network approach to detect stator winding short circuits in asynchronous machines
(Національний технічний університет "Харківський політехнічний інститут", 2023) Sakhara, S.; Brahimi, M.; Nacib, L.; Layadi, T. M.
Nowadays, fault diagnosis of induction machines plays an important role in industrial fields. In this paper, Artificial Neural Network (ANN) model has been proposed for automatic fault diagnosis of an induction machine. The aim of this research study is to design a neural network model that allows generating a large database. This database can cover maximum possible of the stator faults. The fault considered in this study take into account a short circuit with large variations in the machine load. Moreover, the objective is to automate the diagnosis algorithm by using ANN classifier. Method. The database used for the ANN is based on indicators which are obtained from wavelet analysis of the machine stator current of one phase. The developed neural model allows to taking in consideration imbalances which are generated by short circuits in the machine stator. The implemented mathematical model in the expert system is based on a three-phase model. The mathematical parameters considered in this model are calculated online. The characteristic vector of the ANN model is formed by decomposition of stator current signal using wavelet discrete technique. Obtained results show that this technique allows to ensure more detection with clear evaluation of turn number in short circuit. Also, the developed expert system for the taken configurations is characterized by high precision.
Direct power control using space vector modulation strategy control for wind energy conversion system using three-phase matrix converter
(Національний технічний університет "Харківський політехнічний інститут", 2023) Boukadoum, A.; Bouguerne, A.; Bahi, T.
Wind energy conversion system is getting a lot of attention since, they are provide several advantages, such as cost competitive, environmentally clean, and safe renewable power source as compared with the fossil fuel and nuclear power generation. A special type of induction generator, called a doubly fed induction generator is used extensively for high-power wind energy conversion system. They are used more and more in wind turbine applications due to the advantages of variable speed operation range and its four quadrants active and reactive power capabilities, high energy efficiency, and the improved power quality. Wind energy conversion systems require a good choice of power electronic converters for the improvement of the quality of the electrical energy produced at the generator terminals. There are several power electronics converters that are the most popular such as the two stage back-back converter. Because of the disadvantage of these converters to produce large harmonics distortions, we will choose using of three-phase matrix converter. Purpose. Work presents a direct power control using space vector modulation for a doubly fed induction generator based wind turbine. The main strategy control is to control the active and reactive powers and reduce the harmonic distortion of stator currents for variable wind speed. The novelty of the work is to use a doubly fed induction machine and a three pulses matrix converter to reduce the low cost, volume and the elimination of the grid side converter controller are very attractive aspects of the proposed topology compared to the conventional methods such as back-to-back converters. Simulation results are carried out on a 1.5 MW of wind energy conversion system connected to the grid. The efficiency of the proposed system has been simulated and high results performances are evaluated to show the validity of the proposed control strategy to decouple and control the active and reactive power for different values of wind speed.
Efficient method for transformer models implementation in distribution load flow matrix
(Національний технічний університет "Харківський політехнічний інститут", 2023) Kadri, M.; Hamouda, A.; Sayah, S.
Most distribution networks are unbalanced and therefore require a specific solution for load flow. There are many works on the subject in the literature, but they mainly focus on simple network configurations. Among the methods dedicated to this problem, one can refer to the load flow method based on the bus injection to branch current and branch current to bus voltage matrices. Problem. Although this method is regarded as simple and complete, its drawback is the difficulty in supporting the transformer model as well as its winding connection types. Nevertheless, the method requires the system per unit to derive the load flow solution. Goal. In the present paper, our concern is the implementation of distribution transformers in the modeling and calculation of load flow in unbalanced networks. Methodology. Unlike previous method, distribution transformer model is introduced in the topology matrices without simplifying assumptions. Particularly, topology matrices were modified to take into account all winding types of both primary and secondary sides of transformer that conserve the equivalent scheme of an ideal transformer in series with an impedance. In addition, the adopted transformer models overcome the singularity problem that can be encountered when switching from the primary to the secondary side of transformer and inversely. Practical value. The proposed approach was applied to various distribution networks such as IEEE 4-nodes, IEEE 13-nodes and IEEE 37-nodes. The obtained results validate the method and show its effectiveness.
Energy characteristics for nanosecond current interrupter of semiconductor-magnetic pulse generator’s terminal stage
(Національний технічний університет "Харківський політехнічний інститут", 2023) Khrysto, O. I.
A semiconductor diode based on reverse current interruption is used to increase a pulse amplitude and peak power delivered on the process load. Usually, a current interrupter is located in the last stage of semiconductor-magnetic pulse generator (SMPG) and is connected in parallel to the load. Problem. Most of publications on this topic mostly concern with analysis of physical processes in the diode structure itself within its oscillating circuit, which is separated from previous SMPG’s pulse compression stages under condition of unidirectional energy transfer from the generator to the load. In this sense, the efficiency of conversion should be determined by the joint of electromagnetic interaction between non-linear compression stages, current interrupter and process load. Goal. Develop a mathematical model of nanosecond current interrupter to determine its electrical and energy characteristics as a part of high-voltage parallel circuit with magnetic pulse compression, depending on the duration and moment of current interruption, the equivalent circuit for load resistance, and to set the most optimal modes of its operation. Methodology. In this work, it is proposed to use a comprehensive approach aimed at the study of electromagnetic processes in the SMPG’s circuits with a nanosecond current interrupter, which takes into account the topology of circuit, the design parameters of saturable reactor, the magnetization curve, the equivalent load’s resistance, as well as the time parameters of power switches. Results. Analytical expressions describing the electrical and energy characteristics of the interrupter when it operating on the active load are obtained. A numerical simulation of interrupter in the SMPG’s double-loop pumping circuit is carried out, taking into account a nonlinearity of SR’s magnetization curve. Three operation modes of interrupter is described, depending on the initial moment of reverse conduction current interruption. The analysis of interrupter operation on the load with an active-capacitive component is carried out. Practical meaning. The results of research can be applied in development of high-voltage SMPG scheme with improved energy-dynamic parameters.
Energy management based on a fuzzy controller of a photovoltaic/fuel cell/Li-ion battery/supercapacitor for unpredictable, fluctuating, high-dynamic three-phase AC load
(Національний технічний університет "Харківський політехнічний інститут", 2023) Ayat, Y.; Badoud, A. E.; Mekhilef, S.; Gassab, S.
Nowadays, environmental pollution becomes an urgent issue that undoubtedly influences the health of humans and other creatures living in the world. The growth of hydrogen energy increased 97.3 % and was forecast to remain the world’s largest source of green energy. It can be seen that hydrogen is one of the essential elements in the energy structure as well as has great potential to be widely used in the 21st century. Purpose. This paper aims to propose an energy management strategy based a fuzzy logic control, which includes a hybrid renewable energy sources system dedicated to the power supply of a three-phase AC variable load (unpredictable high dynamic). Photovoltaic (PV), fuel cell (FC), Li-ion battery, and supercapacitor (SC) are the four sources that make up the renewable hybrid power system; all these sources are coupled in the DC-link bus. Unlike usual the SC was connected to the DC-link bus directly in this research work in order to ensure the dominant advantage which is a speedy response during load fast change and loads transient. Novelty. The power sources (PV/FC/Battery/SC) are coordinated based on their dynamics in order to keep the DC voltage around its reference. Among the main goals achieved by the fuzzy control strategy in this work are to reduce hydrogen consumption and increase battery lifetime. Methods. This is done by controlling the FC current and by state of charge (SOC) of the battery and SC. To verify the fuzzy control strategy, the simulation was carried out with the same system and compared with the management flowchart strategy. The results obtained confirmed that the hydrogen consumption decreased to 26.5 g and the SOC for the battery was around 62.2-65 and this proves the desired goal.
Field programmable gate array hardware in the loop validation of fuzzy direct torque control for induction machine drive
(Національний технічний університет "Харківський політехнічний інститут", 2023) Aib, A.; Khodja, D. E.; Chakroune, S.
Currently, the direct torque control is very popular in industry and is of great interest to scientists in the variable speed drive of asynchronous machines. This technique provides decoupling between torque control and flux without the need to use pulse width modulation or coordinate transformation. Nevertheless, this command presents two major importunities: the switching frequency is highly variable on the one hand, and on the other hand, the amplitude of the torque and stator flux ripples remain poorly controlled throughout the considered operating speed range. The novelty of this article proposes improvements in performance of direct torque control of asynchronous machines by development of a fuzzy direct torque control algorithm. This latter makes it possible to provide solutions to the major problems of this control technique, namely: torque ripples, flux ripples, and failure to control switching frequency. Purpose. The emergence of this method has given rise to various works whose objective is to show its performance, or to provide solutions to its limitations. Indeed, this work consists in validation of a fuzzy direct torque control architecture implemented on the ML402 development kit (based on the Xilinx Virtex-4 type field programmable gate array circuit), through hardware description language (VHDL) and Xilinx generator system. The obtained results showed the robustness of the control and sensorless in front of load and parameters variation of induction motor control. The research directions of the model were determined for the subsequent implementation of results with simulation samples.
Reactive power optimization in distribution systems considering load levels for economic benefit maximization
(Національний технічний університет "Харківський політехнічний інститут", 2023) Srinivasan, G.; Mahesh Kumar Reddy, V.; Venkatesh, P.; Parimalasundar, E.
The need for electrical energy has been increased sharply due to hasty growth in industrials, social and economic improvements. From the previous studies, it has been agreed that almost 13 % of the total power generated is wasted as heat loss at distribution level. It has been extensively recognized that the node voltage profile along the distribution system can be enhanced under steady state power transfer controlled by proper reactive power compensation. Capacitors have been acknowledged as reactive power compensating device in distribution systems to achieve technical and economical benefits. Novelty of this work is the application of Archimedes optimization algorithm for reactive power optimization in distribution systems so as to obtain an improved solution and also a real 94-bus Portuguese network and modified 12-bus network has been taken and validated for three different load levels which are totally new. Purpose of the proposed work is to maximize the economic benefit by reducing the power loss and capacitor purchase cost at three different load conditions subject to satisfaction of equality and inequality constraints. Methods. The economic benefit has been validated using Archimedes optimization algorithm for three load levels considering three distribution systems. Results. The computational outcomes indicated the competence of the proposed methodology in comparison with the previously published works in power loss minimization, bus voltage enhancement and more economical benefit and proved that the proposed methodology performs well compared to other methods in the literature.
Sensorless control of switched reluctance motor based on a simple flux linkage model
(Національний технічний університет "Харківський політехнічний інститут", 2023) Fan, J.; Lee, Y.
The operation of switched reluctance motor requires prior knowledge of the rotor position, obtaining from either low resolution photocoupler based position sensor or high resolution shaft encoder, to control the on/off states of the power switches. Problem. However, using physical position sensor in harsh environment will inevitably reduce the reliability of the motor drive, in which sensorless control comes into play. Novelty. In this paper, a sensorless control scheme of switched reluctance motor is proposed. Methodology. The method is based on a simple analytical model of the flux-linkage curves rather than the conventional approach that normally uses a look-up table to store all the data points of the flux-linkage curves. By measuring the phase current, rotor position can be deduced from the analytical model. Practical value. Simulation results are given and the proposed sensorless scheme is verified to provide a moderate position estimation accuracy in a wide speed range in both unsaturated and saturated conditions.
Ultimate effect of non-identity of resistive elements of high-voltage arm on frequency characteristics of broadband voltage divider (analytical research)
(Національний технічний університет "Харківський політехнічний інститут", 2023) Brzhezitsky, V. O.; Haran, Y. O.; Trotsenko, Y. O.; Protsenko, O. R.; Derzhuk, A. O.; Dixit, M. M.
Determination in the analytical form of the maximum limiting influence of the non-identity of the resistive elements of the high-voltage arm on the amplitude-frequency characteristic and phase-frequency characteristic of the voltage divider with parallel-series connection of R-, C-elements of the high-voltage arm. Methodology. Based on the previously developed theory of broadband voltage dividers with parallel-series connection of R-, C-elements, analytical expressions for amplitude-frequency and phase-frequency characteristics of the voltage divider are obtained and investigated taking into account the limit case of nonidentical resistive elements of high-voltage arm. Results. The nature of the dependencies of the frequency characteristics of the broadband voltage divider on the value of the tolerance of the resistive elements of the high-voltage arm, the division factor of the voltage divider in a wide range of frequency changes are determined. Simplified approximating expressions for the maximum values of frequency characteristics of the voltage divider are proposed and their error is determined. Originality. For the first time in the analytical form the limiting influence of non-identity of resistive elements of a high-voltage arm of a voltage divider on its frequency characteristics is considered. A mathematical model of this influence is constructed and the limit values of frequency characteristics of the voltage divider are determined. Practical value. It is recommended to introduce into the normative documentation of broadband voltage dividers the corrected value of the division factor, which allows to significantly reduce the deviation of the actual value of the division factor of the voltage divider from the normalized value in a wide range of frequency changes.
Wavelet packet analysis for rotor bar breakage in an inverter induction motor
(Національний технічний університет "Харківський політехнічний інститут", 2023) Abu Ibaid, O. Z. I.; Belhamdi, S.; Abid, M.; Chakroune, S.; Mouassa, S.; Al-Sagar, Z. S.
In various industrial processes, squirrel cage induction motors are widely employed. These motors can be used in harsh situations, such as non-ventilated spaces, due to their high strength and longevity. These machines are subject to malfunctions such as short circuits and broken bars. Indeed, for the diagnosis several techniques are offered and used. Novelty of the proposed work provides the use of wavelet analysis technology in a continuous and discrete system to detect faults affecting the rotating part of an induction motor fed by a three-phase inverter. Purpose. This paper aims to present a novel technique for diagnosing broken rotor bars in the lowload, stationary induction machine proposed. The technique is used to address the problem of using the traditional Techniques like Fourier Transforms signal processing algorithm by analyzing the stator current envelope. The suggested method is based on the use of discrete wavelet transform and continuous wavelet transform. Methods. A waveform can be monitored at any frequency of interest using the suggested discrete wavelet transform and continuous wavelet transform. To identify the rotor broken bar fault, stator current frequency spectrum is analyzed and then examined. Based on a suitable index, the algorithm separates the healthy motor from the defective one, with 1, 2 and 3 broken bars at no-load. Results. In comparison to the healthy conditions, the recommended index significantly raises under the broken bars conditions. It can identify the problematic conditions with clarity. The possibility of detecting potential faults has been demonstrated (broken bars), using discrete wavelet transform and continuous wavelet transform. The diagnostic method is adaptable to temporary situations brought on by alterations in load and speed. Performance and efficacy of the suggested diagnostic method are demonstrated through simulation in Simulink® MATLAB environment.