Three-phase Power Supply System Research Articles

ВИМІРЮВАННЯ ТА КОМПЕНСАЦІЯ НЕАКТИВНИХ ПОТУЖНОСТЕЙ ТРИФАЗНИХ СИСТЕМ ЕЛЕКТРОЖИВЛЕННЯ ЗАСОБАМИ ПАРАЛЕЛЬНОЇ АКТИВНОЇ ФІЛЬТРАЦІЇ

In this paper, the power theory of three-phase power supply systems was further developed by substantiating new formulas for calculating the unbalance power of three-phase four-wire power supply systems based on the measurement of active and reactive powers of individual phases, which can be used to form compensation signals in distributed active filtering with centralized control. A new structural scheme for controlling an autonomous shunt active filter with extended functionality and increased speed is proposed, which can be used in both three-wire and four-wire power supply systems. Computer modeling confirmed the adequacy of the new formulas for calculating the unbalance power components and the effectiveness of the proposed active filtering strategies to minimize power losses in the transmission line. References 11, figures 3, table 1.

A novel cost-effective power supply model for industrial appliances based on triangular magnetic shunt transformer design

This paper presents a new design of a magnetic shunt transformer for use in industrial microwave generators. The proposed transformer has a triangular shape and offers several advantages over existing transformer designs, including reduced volume and maintenance costs. We provide a detailed analysis of the transformer's dimensions and an equivalent model of the three-phase high voltage power supply system. The results of this study have significant implications for the field of industrial microwave generator design and could lead to the development of more efficient and costeffective systems. The resulting model is comprised of saturable inductors capable of accounting for the non-linear phenomena of saturation. The power supply is simulated using MATLAB/Simulink with a neuro-fuzzy ANFIS approach. The results are compared to experimental validations of a single-phase reference power supply for a magnetron, validating the proposed power supply. Additionally, the simulation results demonstrate the effectiveness of the proposed design, which outperforms existing transformers in terms of volume, energy efficiency and maintenance costs.

Increasing the Level of Autonomy of Control of the Electric Arc Furnace by Weakening Interphase Interactions

Steelmaking is one of the most energy-intensive industries, so improving control efficiency helps to reduce the energy used to produce a tonne of steel. Mutual influences between the phases of an electric arc furnace in available electrode movement control systems cause unproductive electrode movements as a reaction to the redistribution of currents among the phases of a three-phase power supply system due to changes in arc length in one of the phases. The nonlinearity of the characteristics of an electric arc furnace significantly complicates the ability to provide autonomous electrode movement control. The approach proposed in this paper, based on the formation of a matrix of mutual influences with variable coefficients, significantly improves the per-phase autonomy of the electrode movement control system. Nonlinear dependences of the mutual influence coefficients as a function of the current increment in the phase in which the disturbance occurred are obtained. Thus, it is possible to practically eliminate unproductive electrode movements in existing control systems by avoiding the traditional use of a dead zone, which reduces the control quality in the zone of small disturbances. The complex of experiments performed using the mathematical model demonstrate that the mutual influence improves the dynamic properties of the electrode movement system in certain operating modes.

РЕЖИМЫ РАБОТЫ ОБОРУДОВАНИЯ В ТРЕХФАЗНЫХ ЧЕТЫРЕХПРОВОДНЫХ ЦЕПЯХ ПЕРЕМЕННОГО СИНУСОИДАЛЬНОГО ТОКА

When substantiating the relevance of the development of non-contact switching devices that provide the redistribution of single-phase loads in three-phase four-wire AC sinusoidal power supply systems. Attention was paid to the modes of operation of the equipment and methods of their calculation. The results of the analysis of operating modes encountered in real electrical installations and having a negative impact on the quality of power supply are presented. The need to apply the data obtained during the development of measures to improve the quality and reliability of power supply was revealed as a result of the analysis of the operating modes of four-wire power supply systems with single-phase consumers.

РЕЖИМЫ РАБОТЫ ОБОРУДОВАНИЯ В ТРЕХФАЗНЫХ ЧЕТЫРЕХПРОВОДНЫХ ЦЕПЯХ ПЕРЕМЕННОГО СИНУСОИДАЛЬНОГО ТОКА

When substantiating the relevance of the development of non-contact switching devices that provide the redistribution of single-phase loads in three-phase four-wire AC sinusoidal power supply systems, attention was paid to the modes of operation of the equipment and methods of their calculation. The results of the analysis of operating modes encountered in real electrical installations and having a negative impact on the quality of power supply are presented. As a result of the analysis of the operating modes of four-wire power supply systems with single-phase consumers, there was revealed the need to apply the data obtained during the development of measures to improve the quality and reliability of power supply.

РЕЗОНАНСНЫЕ ЯВЛЕНИЯ В ТРЕХФАЗНЫХ ЛИНИЯХ ЭЛЕКТРОПЕРЕДАЧИ, ПИТАЮЩИХ НЕТЯГОВЫХ ПОТРЕБИТЕЛЕЙ ЖЕЛЕЗНОДОРОЖНОГО ТРАНСПОРТА

The article is devoted to the analysis of the quality of electrical energy in three-phase power supply systems for 10 kV non-traction consumers receiving power from traction substations, taking into account resonance phenomena. Emphasis is placed on high-order harmonics, which negatively affect the operation of modern electrical equipment. The prediction of voltage and current resonances in three-phase power transmission lines feeding the non-traction consumers was carried out on the basis of calculations in MathCAD. SimInTech simulations were performed to study electromagnetic processes, including estimation of the higher voltage harmonics values taking into account resonance phenomena in consumers.

Three-phase DC/AC power converter with power quality optimization

Introduction— The DC/AC power conversion systems currently used in multiple applications such as alternative energy sources involve power quality problems due to voltage regulations and distortions such as those caused by harmonic distortion. Objective— Develop a power converter prototype that, through a multi-objective genetic algorithm, allows optimizing the energy quality of three-phase inversion systems through the use of multilevel converters. Methodology— The prototype to be used in the power conversion is defined, the output voltage is modeled mathematically, the optimization multi-objective genetic algorithms are developed, the prototype is implemented and its operation is validated. Results— The algorithm developed and implemented in the developed prototype mitigates power quality phenomena associated with short and long duration variations such as swell, sag, undervoltage and overvoltage, avoids the presence of voltage fluctuations and presents a lower harmonic content in all 1% cases. Conclusions— The implemented prototype allows optimizing the power quality of three-phase power supply systems through the use of multilevel inverters, avoiding the presence of power quality phenomena.

Method of Cylindrical Linear Induction Motor Equivalent Circuit Parameters Determination and Performance Calculation Algorithm

Cylindrical linear induction motors (LIM) are currently used in many industrial applications. Task of modeling of electrical machine is of great importance for optimization of processes of design and manufacture of engines with optimal technical characteristics. Traditional approach of construction of mathematical models of asynchronous machines based on classical theory of electrical machines, in comparison with methods of field theory and numerical methods, is much simpler. Structurally cylindrical LIM are distinguished by the absence of transverse edge effects, which contributes to the use of the methods of the classical theory of electrical machines for construction of their mathematical models. In this paper proposes an analytical method of calculation of parameters of equivalent circuit and operating characteristics of cylindrical LIM. In work engine was studied, movable part of which is made in the form of solid steel bar with a copper coating. Equivalent circuits of linear induction motors of various designs (one-sided, two-sided, cruciform, cylindrical) are considered, and assessment of the possibility of their application for research motor is made. Work of cylindrical LIM on industrial mechanisms is characterized by relatively small value of working stroke. For such engines, it is difficult to carry out standard tests, in particular idle stroke test, in order to obtain data for calculation of parameters of the equivalent circuit. The paper proposes a method of experimental determination of parameters of the equivalent circuit. Stator active resistance is measured at direct current, and stator reactance is measured using out-of-rotor method. The remaining parameters of equivalent circuit are calculated according to short circuit experience and engine work mode without load (is taken as an idle stroke experience). It is shown that exact G-shaped equivalent circuit, when calculation of parameters of which active and reactive components of correction factor and active resistance of magnetization branch are taken into account, provides acceptable accuracy in determination of values of equivalent circuit parameters. Algorithm of calculation of work characteristics of cylindrical LAM based on equivalent circuit data is presented. Comparison of calculated and experimental data showed satisfactory results, error is not more than 7%. A new model for decomposition of the total power losses, which includes four components is proposed. Each of the components of the proposed model has a certain physical meaning due to the nature of electromagnetic processes in a three-phase four-wire system. Definitions to describe each of the proposed components are formulated. It is shown that each of supplementary components of the total loss power is proportional to the minimum possible loss power and to the square of the RMS value of the power, which is caused by its occurrence in three-phase four-wire power supply system, and it is inversely proportional to the mean square of the net power loss. The synthesized Matlab-model for verification of the four-component structure of power losses showed a high degree of its adequacy. The proposed model allows us to rethink the description of power losses in three-phase AC circuits and can be used in specialized measuring instruments for electrical networks monitoring. Using the information obtained in the monitoring process, it is possible to plan technical measures to reduce losses of electrical energy in the power supply system, as well as to estimate the capital costs of these measures.

A Decomposition Four-Component Model for Calculating Power Losses in Low-Voltage Power Supply Systems

A new model for decomposition of the total power losses, which includes four components is proposed. Each of the components of the proposed model has a certain physical meaning due to the nature of electromagnetic processes in a three-phase four-wire system. Definitions to describe each of the proposed components are formulated. It is shown that each of supplementary components of the total loss power is proportional to the minimum possible loss power and to the square of the RMS value of the power, which is caused by its occurrence in three-phase four-wire power supply system, and it is inversely proportional to the mean square of the net power loss. The synthesized Matlab-model for verification of the four-component structure of power losses showed a high degree of its adequacy. The proposed model allows us to rethink the description of power losses in three-phase AC circuits and can be used in specialized measuring instruments for electrical networks monitoring. Using the information obtained in the monitoring process, it is possible to plan technical measures to reduce losses of electrical energy in the power supply system, as well as to estimate the capital costs of these measures.

Modeling of three-phase inverter power supply system in Simulink

A model of a three-phase electronic converter of electric energy for an autonomous power supply system has been studied. The objective is measuring the percentage of the higher harmonics in the output of the three-phase inverter voltage and the effect of adding a passive selective Notch filters. Their inclusion in the output circuit creates a model of the system with improved electromagnetic compatibility, and hence an increased power factor and efficiency. A virtual architecture of the three-phase inverter power supply system has been developed in Matlab - Simulink software environment. The invertor is built of separate functional blocks simulating the components that can be embedded in a real project. The schematic diagram includes three-phase symmetric loads with three-phase filters models. The main operation modes of the invertor are modeled and the effects of adding three-phase filters to the output circuit after the voltage inverter are analyzed. From the pulse with modulation simulation, the frequency spectrum for the output current IL and voltage UL has been synthesized.

Вибір системи живлення низьковольтних однофазних електроприймачів повітряних ліній напругою 220/380 В

Two-phase three-wire and single-phase two-wire branches from main three-phase lines are integral components of three-phase four-wire systems. Therefore, the aim of this work is to choose the optimal power supply system for single-phase electrical receivers depending on their power and branch length. The comparison of single-, two- and three-phase power supply systems of single-phase electric receivers is carried out and analytical expressions are obtained to determine power losses, phase voltage loss and wire cross section for allowable voltage loss at the same total active load power and its equal distribution between phases. Based on the obtained expressions, the total power losses, voltage loss in phase and neutral wires for different power supply systems are analyzed. In the transition from a three-phase four-wire power supply system of single-phase electric receivers to a single-phase two-wire or two-phase three-wire system with the same total load power and equal load phases with wire cross sections selected for allowable voltage loss, power loss and phase voltage with a corresponding decrease in their active resistance. It is shown that in some cases the use of single-phase and two-phase branches saves conductive materials in comparison with the three-phase linear branch, the cross section of which is inflated due to the need to ensure the condition of mechanical strength. The dependences of the limiting length of three-phase and single-phase overhead insulated lines, which corresponds to the allowable voltage loss, on the active load power are calculated. It is shown that the limiting length of three-phase linear branches significantly exceeds the limiting lengths of single-phase and two-phase branches at the same load power. The optimal version of the power supply system should be selected on the basis of technical and economic calculation depending on the load capacity, line length and allowable voltage loss.

ВЫБОР И ОБОСНОВАНИЕ ОСНОВНЫХ КОНСТРУКТИВНЫХ ПАРАМЕТРОВ КОНТАКТНОЙ ПОДВЕСКИ ДЛЯ ТРЕХФАЗНОЙ СИСТЕМЫ ТЯГОВОГО ЭЛЕКТРОСНАБЖЕНИЯ НА ПРЯМОМ УЧАСТКЕ ПУТИ

At development of common concept of current collection for three-phase traction power supply system there is the need to select and substantiate main design parameters of catenary suspension. For this purpose, the authors have carried out analytical calculations and developed a numerical mathematical model that allows assessing catenary statics and it’s dynamics in interaction with current collector. On the basis of results of modeling, the authors have substantiated and selected all the required parameters. In particular, they have determined the permissible speed of trains and maximal length of catenary spans.

Analysis of unbalanced load low-voltage electrical networks operating modes

The article discusses distribution electrical networks 0.38 kV operating modes, feeding individual residential buildings. The electrical energy parameters measurement were certified RESURS-UF2M device carried out. The currents and voltages time diagrams based on the measurements made and using Matlab technologies were constructed. It is established that the level of phase currents unbalance is quite high and causes significant three-phase power supply system unbalance voltage accordingly. The power of quality indicators - calculations, characterizing voltage unbalance were made, which were based on the measurements and the computer program “Asymmetry” was used. As well as the additional power losses coefficient determining by the phase currents unbalance, were calculations. Time diagrams these indicators are constructed and their analysis were made. As a result, the power of quality is significantly reduced by unbalance power consumption in the studied electrical network were founded. At the same time, the additional power losses are significant increases. Specific recommendations for the normalization electrical network-operating mode are given.

Active power filter for reactive power compensation for the powerful sounding pulses shapers

The expediency of using a power active filter in the mode of reactive power compensation of the supply network for the powerful sounding pulses shaper power supply system of the Institute of ionosphere NAS and MES of Ukraine is shown. An analysis of the literature has been carried out, which shows the effectiveness of solving the problem of reactive power compensation, filtering higher harmonics of the power supply network using active filtering of higher harmonics of current or voltage using an additional energy source to obtain a compensating signal in the form of current or voltage. The choice of the power circuit for constructing a power active filter has been made. A voltage inverter on IGBT transistors is used as a power active filter. The basic principles of operation of the power active filter control system are described, which are based on the p-q theory of power and provide for the calculation of instantaneous values ​​of the task currents for each phase of a three-phase power supply system. The work of the Matlab-model of the power supply system of the shaper is shown, the oscillograms of the main energy characteristics of the shaper are given. As a result of using a power active filter, the current of the supply network becomes close to sinusoidal, and the power factor tends to 1. A positive effect on the efficiency of the shaper when the power active filter is included in the supply network is noted, which is due to the efficiency of compensation of the reactive power consumed by the shaper from the supply network. The simulation results are presented, in particular, graphs of reactive power change at the point of connecting the power active filter to the supply network, at different levels of reactive power consumption by the shaper. The results obtained confirmed the possibility of using a power active filter in the mode of reactive power compensation of the supply network when solving the problems of improving the electromagnetic compatibility of powerful sounding pulses shapers with the supply network, reducing losses and increasing the reliability of the shapers. Keywords: active power filter, reactive power control, control systems

Analysis of energy flows in the power supply system with a thyristor voltage converte

A numerical analysis of energy flows in a three-phase power supply system with a sine wave EMF source, active load and a thyristor converter that distorts the sine waveform and generates higher harmonics is performed. The influence of the thyristor non-sinusoidal voltage on the energy flows and the power factor of the source is analyzed. Thyristor converter is considered as a nonlinear electric power unit consuming electricity from the primary power source at a fundamental frequency, part of which is converted and returned back to the network as a secondary energy stream of zero-sequence systems and higher harmonics, thereby reducing the overall power factor and the quality of electricity becomes worse. It is analyzed the influence of the considered harmonics quantitative composition on the accuracy of the currents and voltages calculations. The dependence of the higher harmonics amplitudes on the thyristor firing angle is established. The constant component and the 2nd order harmonic voltage are the most denoted in the thyristor harmonics spectrum. In general case it is shown that in the nonlinear circuit with a sinusoidal power source, even in the absence of inductive and capacitive electric load, the fundamental current harmonic of the power source does not coincide in phase with the sinusoidal EMF of the source. Thus, the thyristor can be considered as a reactive inductive element that consumes reactive power of the fundamental frequency of current, regardless of the its firing angle and the presence of other reactive elements in the system. Therefore, in order to increase the power factor, it is necessary to compensate the reactive power of displacement only at the current fundamental frequency, which should be recorded by electronic meters. It is proposed to use the relative current value of the first harmonic of the power source to characterize the effect of the secondary energy flow on the total power factor. In a four-wire network, the presence of a thyristor converter causes a significant current increasing in the neutral wire, even under symmetrical phase loading, due to the zero sequence currents flowing, which are multiple of three, and they must be taken into account during wire cross-section selection and power losses calculation. It is proposed the practical measures to limit the level of higher harmonics and improve the electricity quality.

Дослідження електромагнітних процесів у перетворювачі з тризонним регулюванням напруги

The article focuses on electromagnetic processes in electric circuits with semiconductor switches. A mathematical model of a semiconductor converter with three-zone output voltage control has been created so as to analyse electromagnetic processes in semiconductor converters with pulsewidth control. The graphs showing electromagnetic processes in electric circuits are given. The mathematical model of the semiconductor converter is also used to study transients in semiconductor converters with actively-inductive load. The method of multiparameter functions, which are included in the algorithmic equations to analyse steady-state and transient processes in branchy circuits with semiconductor switches and reactive elements, has been improved by using the peculiarities of phase and linear voltages in the power supply grid. We have developed a new mathematical model of steadystate and transient processes in electric circuits of semiconductor converters of modulation type with multichannel zone usage of phase voltages of a three-phase power supply system without considering power losses in switches to quickly evaluate the influence of load parameters on the regulated sine and constant voltages. The results of this work can be used to develop the method of multiparameter modulating functions to simplify the analysis of transients in electrical circuits without taking into account the losses in key elements.Ref. 4, pic. 3

Equivalent Scheme for Calculating Short-Circuit Current in an Alternating-Current Electric Traction Network

The authors have proved the feasibility of substitution of a three-phase power-supply system with a single-phase one when calculating three-phase circuits in electric traction network irrespectively of the external power supply arrangement. In addition, calculation features have been established for particular transformer winding connection configurations (Y/Y or Y/Δ). Based on results of an analysis performed for minimizing the methodological error in calculating the short-circuit currents, a single-phase equivalent circuit has been developed for the intersubstation zone of the traction network, which takes into account the connection between two adjacent substations via an overhead transmission line of 110 (220) kV. An example of calculation in accordance with the proposed replacement scheme is given.

Graphoanalytic determination of symmetry parameters and total compensation of reactive power for a three-phase power supply system

Problem. The simulation of currents and voltages in electric three-phase power supply systems is an important means of improving the quality of electrical supply. It is precisely the alignment of the values of currents in the phases of electricity supply lines, thus, the power supplies are loaded evenly. In addition to the symmetry to reduce losses in the transmission of electrical energy, it is necessary to provide transmission from the source to the loading of only active power. Therefore, it is necessary to determine the parameters of symmetric-compensating devices, which, given the fact that active-reactive line resistance is taken into account, is a rather complicated task. Numerical optimization algorithms are used to solve this problem, the disadvantage of which is the possibility of not receiving a solution due to unsuccessful selection of initial approximation of parameters and (or) excessive number of computational operations. To solve such problems, symmetro-compensating devices are used. The need to take into account the influence of active-reactive resistance of transmission lines with accurate calculation of the parameters of symmetro-compensating devices requires the use of computer models and numerical optimization methods and subroutines. Goal. Development of the method of determining the parameters of the symmetrical device for three-phase power supply systems, based on the analysis of the existing operating mode of the system with subsequent graph-analytical determination of the parameters of the symmetry and full compensation of reactive power. Methodology. The complex methods of analysis of linear electric circuits are used. To determine the requirements of symmetry and compensation, the method of symmetric components is used. To determine the parameters of the compensating device, methods of analytic geometry are used, as well as matrix methods for solving systems of linear algebraic equations. Results. The proposed method allows graphoanalytic way to obtain a numerical solution to the problem of symmetry of currents in the line and compensation of reactive power in a three-phase power supply system with asymmetric load. It has been established that the parameters of the symmetric device, determined from the data of the initial analysis of the mode of operation of the power supply system with an asymmetric load, do not always provide a sufficient effect of symmetry and compensation. To improve the efficiency of the symmetry and compensation parameters of the simulating device should be specified according to the primary compensation. Originality. It is proposed to make an initial assessment of the mode of operation of the power supply system. Based on the initial assessment, the primary requirements for the parameters of symmetry and compensation are determined. Approximate values of the parameters of the symmetry and compensation are determined by processing the initial requirements by methods of analytical geometry. The effect of primary symmetry and primary compensation was estimated, and the primary requirements were clarified. After the correction, the full effect of the symmetry of currents and the compensation of reactive power in the lines of the power supply system have been achieved. Practical value. The proposed method allows to calculate the parameters of the symmetric compensation devices with high accuracy taking into account the resistance of lines in power supply systems with a wide range of changes in asymmetry and reactivity of loads, which ensures reduction of losses due to excessive asymmetry and reactivity of consumers.Key words: three-phase system; asymmetry; symmetrical device; reactive power compensation.

RESEARCH OF THE MODES OF FULL COMPENSATION OF REACTIVE POWER IN A THREE-PHASE POWER SUPPLY SYSTEM

Introduction The article is devoted to the issues of current balancing and reactive power compensation in a three-phase power supply system. Optimal in all these respects is the mode of full compensation of reactive power, by which we mean such a symmetrical mode, in which only active power is consumed from the source. The task of calculating the mode of full reactive power compensation is non-linear and can be solved using non-linear optimization methods based on the adopted parameters and optimization criteria. The objective of the article is to develop a visual model of the power supply system with an unbalanced load, in which current balancing and reactive power compensation is performed using a symmetrical-compensating device, which parameters are determined using search non-linear optimization tools and modern computer mathematics software packages. The purpose of the article is to research the modes of full compensation of reactive power in a three-phase power supply system with a linear asymmetric load in order to identify the ambiguity of solving the problem of synthesizing parameters of a reactive power compensator. Methodology of research consists in the development of a visual model of a power supply system that feeds unbalanced load. As a symmetrical compensating device, capacitors connected between the phases of the transmission line are used. The model is controlled by a program that launches the model and performs optimization and selection of optimization variable values. The optimization values are the capacitors of the symmetry-compensating device. The optimization criterion is a spherical metric consisting of the reactive powers of each source of electricity. Results lead depending on the choice of the initial values of the optimization variables, the optimization process enters two modes of full compensation of reactive power – main and additional. The main mode is characterized by small values of capacitors and small values of currents, and in the additional mode, these values of the system and operational parameters reach extremely large values that are unacceptable for practical use. Originality lies in the fact that in terms of optimization theory this means that there is no global optimum in the solution of the problem of full compensation, however, there are two local optimums. Both modes are stable, as evidenced by modeling on the SPS-model of the system in the time domain in the space of state variables. Practical significance of the work lies in the fact that when designing a microprocessor system that optimizes the operating mode of the power supply system, it is necessary to envisage the situation of additional mode.

МЕТОДИКА РОЗРАХУНКУ ЕНЕРГОЗБЕРІГАЮЧОГО ЕФЕКТУ ВІД ЗАСТОСУВАННЯ ПАРАЛЕЛЬНОГО АКТИВНОГО ФІЛЬТРА В ТРИФАЗНІЙ ЧОТИРИПРОВІДНІЙ СИСТЕМІ ЕЛЕКТРОЖИВЛЕННЯ З УРАХУВАННЯМ ЙОГО ВЛАСНИХ ВТРАТ

The deduction of settlement ratios and the development of a method for calculating the energy saving effect from the use of a shunt active filter in a three-phase four-wire power supply system and its testing on the example of monitoring the parameters of electricity consumption of the hostel number 7 KNUTD.