Статьи журнала - Вестник Южно-Уральского государственного университета. Серия: Энергетика
Все статьи: 738
About the dynamics of some methods of integrating conversion of analog signal into digital code
Статья научная
The new principles of constructing of the clocked reversible integrating analog-to-digital converters (ADCs) with pulse-width (PWM) and in-phase amplitude-frequency-pulse modulation (AFPM), as well as closed integrating ADC with tactless bit-by-bit equilibration is considered. The block diagrams and time diagrams of the ADC are reduced. An analysis of their dynamic characteristics is given. It is shown that the expansion of bandwidth of the ADC with PWM is possible by increasing the number of cycles of sweep conversion "within" the synchronization interval. In particular, it is proved the ADC with inphase AFPM in comparison with the known technical solutions has at least an order higher temperature and time stability of the characteristics. The bandwidth of the closed integrating ADC with tactless bit-by-bit equilibration depends on the time constant of channel integration. Significant expansion of the ADC bandwidth which purchased due to the reducing of the metrological characteristics is possible in his open-loop structure in the deficiency of channel integration.
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Adaptive interval-code synchronizing units
Статья научная
The synchronizing units adaptive to instability of the mains voltage amplitude for the network forced power semiconductor converters are considered. In order to reduce switching and pulse interference in the synchronizing unit with tracing fixation of self-switching points the first-order aperiodic filters are used, regulated to the shift of input sinusoidal voltage to the angle of minus 30 or 60 electrical degrees that is determined by the level of interference from mains voltage. As a result the auxiliary three-phase voltage system is created which is processed further with the help of comparators and binary-decimal decoders. From the gained series of numbers the needed ones are chosen and combined by the function “OR”. The logic signal is gained as a result, the width of which corresponds to the required synchronization interval of the semiconductor converter. In the second case the synchronization signal affects the self-oscillating integrating sweep converters transferring them to the forced switching mode with the mains voltage frequency. Together with this each of the synchronization channels gets the properties of the first-order aperiodic filters with time constant determined by the value of the amplitude and frequency of mains voltage. The closed-circuited structure of the sweep conver¬ters and the presence of the integrator in the direct control channel contribute to the high level of metrological characteristics of such synchronizing units. The waveform diagram of the synchronizing units and the recommendations concerning the choice of the parameters of their elements are given.
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Artificial neural networks of technical state prediction of gas compressor units electric motors
Статья научная
Issues of engineering effective and reliable systems for on-line diagnostics of electric motors of electrically driven compressor stations are considered. The paper provides failure statistics for the most critical gas-transport systems’ units - electrically driven gas-compressor stations. Artificial neural networks methodology and architecture were developed to obtain prediction models of MW electric machines. Examples of neuro-fuzzy prediction of synchronous machines stator winding performance and service life are given. Selected network tests, the Box-Jenkins fuzzy model, models of the analysis technique of spectral components dynamics, current magnitude and stator temperature prediction are received. Based on results of comparative analysis of anticipated conditions of electric machines for main gas transport with due regard to various operational factors of electrically driven gas-compressor units, recommendations on application of the artificial neural network method have been drawn up.
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Combined electric power plant simulation model
Статья научная
The article is dedicated to a simulation model of a wind/solar power plant. A variable speed diesel generator set is used as a backup energy source. A matrix frequency converter is used to control frequency of the generated voltage. The simulation model is implemented in the MATLAB Simulink environment. Oscillograms of currents and voltages are obtained when the model operates with an active inductive electrical load with the variable load value in the 1000-4000 VA range. During operation with a rated power load, the deviation of the line voltage parameters lies within the normal range (load voltage drop does not exceed 4% of the nominal value, total harmonic distortion does not exceed 2% in the 0-2000 Hz range). The constructed model can be used in the design of energy facilities, as well as in the development and testing of algorithms for control and monitoring systems.
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Common dataware of a proprioceptive robot control system
Статья научная
The paper is devoted to the peculiarities of the Common Dataware for a significant part of manipulation robots. They have only a proprioceptive feedback system supplying information about position of “arms” and “hands” segments in joints. It outlines disadvantages of the Common Dataware generation based on incremental transducers and sensorless structures. Major parameters that determinate indicators of energy informational practice providing energy conversion into functional displacement of the robot working gear are revealed. The use of a resolver as a primary sensor is recommended, as it has the best noise immunity, shock, vibrations and temperature change resistance compared to other sensors. The “Resolver-to-Digital-Converter (RDC)”combination realizing the time and space binding corresponds to the general relativity postulate. A significant advantage of the proposed RDC solutions is a synthesis of digital equivalents of displacement components, which is implemented without a systematic error based on rigorous trigonometric algorithms. They provide resolution up to 20 bits in a range of 360° at its quadrantal or octantal split.
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Constraining the dynamic torque of a rolling mill stand drive
Статья научная
We herein consider issues of limiting the dynamic loads in the electromechanical systems of horizontal rolls in the stand of a plate mill. It is shown that shock loads mainly occur during gripping due to gaps in spindle connections; the size of the gap depends on how worn-out those spindles are. We analyze a method of limiting such dynamic loads that consists in gripping workpieces while accelerating the electric drive. We also task ourselves to prove the feasibility of implementing this method at the 5000 rolling mill employed by PJSC Magnitogorsk Iron and Steel Works (MMK). We present the oscillograms of workpiece gripping in accelerated and decelerated modes; those oscillograms prove how efficient pre-setting the gap size is. The paper contains a control chart that ensures electric drive acceleration before gripping. We have developed a mathematical model of the dual-mass electromechanical roll system for reversing stands and present herein the parameters of the simulated object. The proposed dynamic load limitation has been simulated. We herein specify a minimum timeframe between the onset of pre-acceleration and the load application moment, which timeframe is necessary for angular gaps to be fully closed. The timeframe value is explained. We have also implemented the developed speed control algorithms in the APCS of the 5000 rolling mill stand. The paper presents the torque and speed oscillograms for the workpiece gripping. It is proved that the torque overshoots in the upper- and lower-roll electric drives is reduced to acceptable levels by this method. We also analyze the oscillograms of the lower-roll drive parameters obtained over nine reversing-rolling passes. It is confirmed that the dynamic torque of grip does not exceed 25% of the steady-state torque. We thus conclude that this speed control method has proven efficient for the stand electric drives of the 5000 mill. Expanded implementation of this method in the existing hot-rolling mills is noted as practical.
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Design and simulation of a solar-wind stand-alone system with a seven-level inverter
Статья научная
During an energy conversion process, the total harmonic distortion and losses will increase while its power stability decreases. Multilevel inverter technology can be utilized to alleviate the shortcomings of conventional inverters. These technologies have become recognized as cost-effective solutions for a wide range of industrial applications. Reduced component losses and lower switching losses, as well as improved output voltage and current waveforms are the first advantages of this design. In multilayer inverters, elimination of harmonic components in the inverter output voltage and current is crucial. This paper proposes a system that consists of three different renewable energy sources. Two of them are PV solar systems while the third is wind turbine simulated in MATLAB Simulink. Seven-level inverters based on switch reduction techniques are proposed in this paper. The proposed system design is verified in the absence of PV systems to produce five voltage levels as a contingency in PV systems.
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Design of observer of flux linkage of synchronous drive of rolling mill
Статья научная
The paper considers the design of control system for variable-frequency synchronous drive with vector torque control. Such drives are used in units with enough wide speed range and shock loading, for example, hot and cold rolling mills. Two coordinates generate the torque of the systems under consideration: current and flux linkage of the stator. This paper provides parameter calculation for the observer of flux linkage state of the stator of synchronous motor with damper windings. The system is implemented based on the Luenberger observer with error-feedback. Flux linkage is determined within the orthogonal coordinate system d, q rotating synchronously with the rotor. The complex of a synchronous exited motor and state observer has been modeled. Modeling results demonstrate that a fractional error of flux linkage generation does not exceed 0.15 %.
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Diagnosis of the electric drive of the discharge roller conveyor of a wide-strip hot mill
Статья научная
The purpose of the study is to develop an automated system for technical diagnostics of the state and regulation of the electric drive of the rollers of the collector roller table at a wide hot rolling mill based on change in the load currents of the rollers electric motors. The system allows the quality of finished rolled products and the productivity of the mill to be enhanced due to the timely detection of faulty equipment and its rapid replacement based on the results of diagnostics. The following methods of diagnostics of the electric drive of the diverting roller table and its possible malfunctions which can negatively affect the quality of the finished rolled products were analyzed: experimental identification of the relation of the forms of change in the load currents of the electric motors of the rollers with specific types of malfunctions; determination of diagnostic signs of malfunctions in the values of change in the load currents of the electric motors of the rollers; creation of a mathematical model for calculating the forces of strip transportation; development of methods and algorithms for technical diagnostics of the electric drive of the collector roller table based on characteristics of change in the load currents of the electric motors of the rollers; development of a generalized algorithm for the operation of the automated technical diagnostics system; experimental evaluation of the effectiveness of the proposed methods and algorithms for diagnostics on the operating mill. Analytical methods of solving algebraic and differential equations and systems were used in the study. As a result of the research, the technical effectiveness of the methods and algorithms developed to diagnose the eccentricity of the roller barrel of the diverting roller table, malfunctioning of the brush-collector device of the roller electric motor, the destruction of the couplings in the roller electric drive line, malfunctioning of the bearing units in the roller electric drive line or the roller sides, the correct alignment of the roller relative to the technological plane of the diverting roller was experimentally confirmed. The diagnostic methods and algorithms developed can be used to create diagnostic systems for electric drives of diverting roller table at operating mills during their reconstruction, as well as at newly built mills. The system thus developed was installed at the industrial plant's 2000 hot rolling mill.
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Статья научная
The paper considers electric traction drive with the field regulated reluctance machine (FRRM). The FRRM principles of operation and main advantages compared with asynchronous machine and synchronous reluctance machine are presented, disadvantages are marked. Mathematical model of the drive with FRRM is described; adequate accuracy is proved by the statistical data processing. The paper presents electric drive operating point determination in the static mode, transient model analysis, which takes into account electrical, electromechanical and mechanical processes of electric traction drive, present the first stage of optimization. The second step explains a method of increasing the maximum speed of the drive. The third stage is associated with optimization of FRRM features with over-torque. Therefore, the drive is obtained with improved weight and dimension characteristics, overload capacity, which meets the requirements of the haulers. Weight-size parameters optimization, three-stage characteristics optimization estimate the most favorable parameters of the control system and the motor. The explanatory drawings are given in the article.
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Electrical load control systems based on wireless data networks with self-organizing topology
Статья научная
The article provides an overview of modern wireless communication protocols used in residential automation systems to solve the problem of powerful household electric loads remote switching. A comparative description of the existing wireless communication protocols is provided. The existing components range is analysed for availability and the possibility of their application in the commercially available control systems. The review of modern wireless technologies serves as a basis to select the technology of self-organizing networks with ESP-MESH mesh topology to set up the remote control of electrical loads in residential building automation systems. The authors consider its advantages, including the most important one, i.e. the IP addressing, and the resulting high integration with such widespread network technologies like Wi-Fi and Ethernet, which is relevant for this application. The proposed option allows for the design of the automation systems for residential buildings to solve the problems of ensuring communication reliability by means of the network topology self-organization, covering the zones, the dimensions of which exceed the communication range of traditional point-to-point systems. At the same time they ensure the security of data transfer due to the data provided by the developers of the ESP-protocol MESH and encryption technology. In this case, the dependence of the probability and conditional probability of establishing a connection on the number of closed transits (disconnection between network nodes) was considered.
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Electrotechnical complexes of heliotechnical devices: a generalized classification
Статья научная
The need to systematize the existing electrotechnical complexes of heliotechnical devices (ECHD) is due to their growing quantity, diversity, and element base. In the proposed publication, a generalized classification of the ECHD is made over a wide range of parameters that characterize the ECHD as a separate class of devices, as their diversity and features are sufficient to describe the ECHD as such. The classification herein proposed analyzes in detail the whole structure and possible layout solutions, an effort enabled by the well-developed modern elemental base for the design of the ECHD. Using this classification enables a more precise, detailed and verified structural synthesis of the ECHD, which will help the solar engineering engineer to better understand and justify a set of technical solutions in the design, construction and operation of ECHD classes. Only electric drives are considered.
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Energy efficient power supply systems of oil and gas pipelines electric drives
Статья научная
The current state of development of autonomous power supply systems is considered including the facilities of gas-transport systems. The use of electric power alternative sources on the base of wind plants in the combined generating complexes is substantiated. The options of electric networks structures with the use of wind plants are suggested for along-the-route consumers. Power effective invariant systems on the basis of combined units under the scheme “synchronous generator - frequency converter” are analyzed. The authors received the predicted amount of generated electric power by power suppliers at wind stream stochastic nature. A number of examples of introduction of the new combined systems of autonomous power supply using renewable power sources in the main gas pipelines of the Russian Federation are given.
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Статья научная
The article presents an experimental investigation, performed to evaluate the hydrodynamics and heat transfer characteristics in tandem arranged heated rows packed inside cylindrical channel, which use air as well as air/water mist flows as operational medium. The average surface temperature has been recorded under various air main flow, water mist rate, surface heat flux and constant pitch ratio (y/d = constant). The heat transfer rate was found to increase with the water mist rate and decrease with the surface temperature. Heat transfer rate was enhanced over that for the single-phase air flow as a result of water mist evaporation and direct heat conduction by the water film generated on the heated surfaces. Overall, the heat transfer coefficient was enhanced by about 140%, 42%, and 10% respectively for the upper, middle and lower heated rows by suspending (111.68 kg m-2 hr-1) water mist rate. The frictional resistance for air/water mist flow is found to exceed that in the single-phase air flow. Compared to each water mist rate over the investigated range, the percentage enhancement in the overall heat transfer performance factor of around 116%, 35%, and 10% respectively for all the heated rows under the highest water mist rate. New experimental results obtained can be used in the development of heat exchanger modules design processes.
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Features of frequency analysis of torque control loop in AC electric drives
Статья научная
In the article, the structural scheme of the synchronous motor torque control channel is shown and mathematically described. Passing of a sine signal in the torque control loop is considered, equations for describing the dynamic properties of the current control loop are given. Specific features relating to the frequency characteristics of the channel for controlling of the electromagnetic torque in the adjustable variable speed drive with synchronous electric machines are considered. The control channel is regarded as a linear system with amplitude modulation. A comparative analysis of the experimental and calculated Bode plots of the current and torque control loops is carried out.
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Impacts of voltage dips in doubly fed induction motor for wind turbine generation systems
Статья научная
Renewable Energy Sources (like wind energy) minimize the demand for other types of power. Wind energy generation has become a major power in some countries, covering the essential share in the Energy Balance in Holland, Spain, Brazil, Germany, China and others. The construction of new Wind Power causes new challenges for the transmission distribution infrastructure. However, environmentally friendly Renewable Energy has recently become an important part of generation in industrial applications, worth for distributed lines expansion. A significant part of electric machines used in Wind Industry are doubly fed induction motors (DFIM) used as electric generators. They earned the leading market position over the recent decade and continue their run. The machines of this type offer operation stability along with affordable costs. The outstanding technical benefits include the ability for variable speed operation and independent control of reactive and active power. To protect the rotor side converter (RSC) from transient overcurrent during voltage dips, the crowbar circuit protection is usually used. The paper analyzes and investigates the dynamic behavior of the doubly-fed induction motor, back-to-back converter, and the rotor side converter during symmetrical voltage dips using the crowbar protection system with MATLAB/Simulink simulation. In addition, it studies the crowbar circuit affects the diodes, switches, and resistances at the low voltage ride through (LVRT) capability enhancement.
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Статья научная
Рассмотрено применение MATLAB-моделирования с целью получения исходной информации для конструирования и разработки дизайна компенсированной системы электроснабжения буровой установки.
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MPPT for hybrid wind, solar and thermoelectric power generation systems for off-grid applications
Статья научная
Renewable energy resources for electrical generation are normally free but are not continuously available due to their sporadic availability. Thus, hybrid connections of various kinds of energy are made to increase utilization of renew-able energy. This paper involves a design of a hybrid renewable energy system employing maximum power point tracking (MPPT) techniques. The hybrid system consists of solar PV panels, a small-scale wind turbine, and a thermoelectric generator (TEG) module. Four MPPT techniques are examined in this research. They are the incremental conductance (IC) algorithm, fuzzy logic controllers (FLC) using 25 and 35 rules, and an interval type 2 fuzzy logic con-troller (IT2FLC). Each MPPT technique is tested in the system to determine which has the best maximum power tracking, stable operation, and efficiency. All of the studied energy resources are connected to a DC linked bus. The voltage of this bus is supplied to a three-phase inverter. Inverter output voltage is regulated for balanced and unbalanced loads. The generating capacity of the designed hybrid system is 5 kW and the system is simulated using MATLAB Simulink R2017a.
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Mathematical model of induction motor with series-connected stator and rotor windings
Статья научная
To provide for the cost-effective use of resources and energy conservation it is vital to enhance unregulated electric drives of copious working mechanisms. The technical process of these mechanisms requires relatively longstanding speed reduction under low static loads. Moreover, another relevant issue is choosing control systems of electric drives in the mentioned systems in accordance with the economic and maintenance aspects. The authors suggest using the systems of impulse-vector control system with wound rotor induction motor that have one essential drawback - the shaft encoder installation. The replacement of the shaft encoder with sensorless impulse-vector control system is complicated due to the lack of proper mathematical description of the electromagnetic processes in schemes with non-traditional windings stator and rotor connection. To solve this problem the authors have developed a mathematical description of impulse-vector control system with wound rotor induction motor supposed to be multiphase and asymmetrical. Angular dependencies of inductances, flux linkages, voltages of engine windings, circuit current and electromagnetic torque relatively to rotor location are derived. In addition to that, the mathematical modeling and research of induction motor configuration with a series connected windings fed by AC voltage source are presented. Equating rotor position in impulse-vector control system with wound rotor induction motor is considered possible through angular dependencies of drop voltages on stator and rotor windings.
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Mexbios - среда разработки современных систем управления электроприводов
Статья научная
Рассмотрен принцип построения и функционирования инструментария для разработки и отладки программного обеспечения современных цифровых систем управления высокоточных электроприводов. Сложность освоения и применения языков программирования создаёт дополнительные барьеры перед техническими специалистами при реализации своих идей в области управления сложными электромеханическими объектами. Разработанный программный комплекс MexBIOS обеспечил значительное сокращение сроков разработки электронных модулей управления, получение необходимых внешних характеристик и снижение стоимости микропроцессорных систем управления электроприводов. Программный комплекс представляет собой интегрированную среду автоматизированного проектирования с возможностью отладки и настройки цифровых систем управления электроприводами. Если первые версии MexBIOS обеспечивали разработку микропроцессорных систем управления электроприводов в режиме реального времени и программы, полученные средствами MexBIOS, имели достаточно громоздкий вид, то для обеспечения наглядности и компактности схем была выработана новая концепция создания структуры программного комплекса. Стало возможно создавать разветвлённые алгоритмы. Впоследствии была реализована возможность в процессе анализа синтезируемого программного обеспечения, выделить различные состояния объекта управления и строго описать действия системы управления в этих состояниях. В настоящее время реализована возможность изменения программного обеспечения без остановки выполнения программы для изменения структуры программы управления, не останавливая технологический процесс. Получены аналитические соотношения и определена методика синтеза векторной системы управления частотно-регулируемым асинхронным двигателем методом визуального программирования в новой программной среде MexBIOS.
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