Stanimir Valtchev

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• Professor
• Professor Emeritus at Universidade NOVA de Lisboa

Abstract—The process of moving flexibly suspended cargo is accompanied by the appearance of loads on the metal structures of the bridge crane and on the electromechanical part of the electric drive due to the rocking of the transported cargo. Limiting this process, and if possible, its complete cessation, is an urgent task, for which many meth...

Abstract—Energy-saving approaches are widely used at enterprises of various profiles. Control systems of devices used to impart homogeneity to compositions often require improvement, since the systems mainly used at these facilities do not have feedback on the viscosity of the mixed composition and do not respond to this indicator by changing the e...

Abstract—The ventilation and air conditioning system is a complex system in production facilities. Mathematical modeling of the ventilation and air conditioning system requires modeling of the building itself, as well as the operation of nodes, units of indoor and outdoor ventilation equipment. This article is devoted to the application of neighbor...

Abstract — In the proposed work, the study of a section of the shop network of an industrial enterprise with the determination of the equivalent circuit resistance. The calculation method presents the errors in the failure to take into account each of the considered parameters of the network. Causes and main damages of switching devices for voltage...

Abstract—In this paper, a comparison, between two LCL filter design methods, for cascaded h-bridge multilevel inverter applications, is performed. In detail, the first one was already proposed by the authors in a previous work. However, to validate the method broad applicability, it is now characterized for a seven-level cascaded h-bridge. The seco...

Abstract – The proposed article is devoted to the evaluation of reliability indicators of in-plant power supply systems with dual-transformer substations 10/0.4 kV. The paper considers the reliability of the system for the following variants of power supply schemes: without redundancy; with redundancy when installing a sectional circuit breaker; wi...

Abstract – The proposed article is devoted to the assessment of reliability parameters of in-plant power supply systems with 10/0.4 kV double-transformer substations. The paper studies the reliability of the power supply system for the following variants of two-transformer substation schemes: without redundancy; with redundancy when installing a se...

Abstract — The paper develops regression models of dependences of the estimated service life of cable line insulation on the load factor in various operating conditions. The study of thermal modes using approximation functions of the obtained results is carried out. The temperature parameters of the cable line with different types of insulation hav...

RELEVANCE. The paper presents a method for calculating the temperature parameters and service life of cable lines (CL) with a voltage of 10 kV for various types of insulation and operating conditions. Dependencies have been developed that are recommended for clarifying the parameters of the CL, taking into account different operating modes. The res...

The study of technical parameters of low-voltage switching devices of Russian production – magnetic starters PML and switches RE19 has been carried out. The problem of evaluating energy efficiency of operation of magnetic starters and switches installed in in-plant power supply systems has been presented. The main destabilizing factors significantl...

For control assessment of defectiveness of low-voltage devices it is proposed to use thermal indicators of the state, which depend on the contact heating temperature. Values of contact heating temperatures from applied materials and type of contacts are investigated. The optimum values of loading coefficients of circuit breakers and contactors are...

Cable lines (CL), as it is known, are one of the main ways to transfer electricity from a substation to consumers. But often their actual service life (Tsl) turns out to be less than the passport one due to overloads due to incorrect choice of cross-section or methods of operation, which lead to thermal breakdown and acceleration of the reaction of...

The work is devoted to the modernization of a device designed for mixing substances with different degrees of viscosity; often, control systems for such objects operate with the same, predetermined, time indicators that cannot be changed at all stages of the formation of the finished composition. Such operating modes are often a consequence of ther...

Industrial facilities of Kazan, as it is known, have in their composition technological cycles of varying degrees of complexity and the corresponding electrical equipment of the shop-floor power supply systems, to the reliability of operation of which, the requirements in modern conditions are significantly increasing. At present, new approaches ar...

During a long time, DC motors were used for mechanisms transporting heavy-weight loads, but the operation of those drives caused a number of problems due to their more complex design features, higher price, and weighty dimensions. An alternative to the DC type of motor at the moment is the two-phase motor, which is capable of taking on large loads...

Abstract — This work presents a methodology for calculating the thermal modes of operation of 10 kV cable lines (CL) at different operating conditions and types of insulation. As a result, formal dependencies are shown, which clarify the parameters of the CL, considering their operation and temperature. The results are useful, reducing the number o...

Abstract — The paper presents a method of monitoring the technical condition of electrical equipment on the basis of thermographic control. This method is also effective in monitoring the contacts of most switching devices. With timely detection of defects in the contact connections of electrical equipment, the probability of preventing emergencies...

Abstract—In this paper, a grid-forming control technique, called synchronous power control, is applied to a cascaded hbridge multilevel inverter, to verify its contribution to frequency and voltage regulation, which are crucial to the power system stability. The key novelties of this work are the application of the synchronous power control to a ca...

Abstract—This paper shows a different controller procedure for power electronics converters that insert in the grid energy generated by renewable sources like photovoltaic or wind turbine, into micro-grids. Virtual Synchronous Generators (VSG), the name of the category of these smart converters, work in cooperation with main grid or in lonely and s...

Abstract—The article discusses a device designed for mixing substances of different viscosities. Typically, devices of this kind have a control system that allows the object to function with the same time parameters, both when mixing ingredients and when stopping the mechanism. The consequences of this operating cycle are often thermal overheating...

Abstract—The paper studies the technical parameters of low-voltage switching devices. The main factors influencing the technical characteristics of devices are given. The dependence of the contact heating temperature of the apparatus on the loading factor is revealed. It is proved that with the increase of loading of devices the temperature of heat...

The unidirectional hybrid three-phase rectifier (UHTR) with Boost converter consists of two different rectifiers (Rectifier 1 and 2), where Rectifier 2 consists of modules corresponding to the phases. Each rectifier processes different part of the current waveform at the input, so that the sum of the current waveform parts is sinusoidal, or multile...

Research activities in the field of development of electrical power and electrical equipment include the development of new approaches to assessing the reliability indicators of electrical equipment elements and in-house power supply systems in general. The study has examined methods for assessing the reliability of electrical equipment in intra-sh...

The study of technical parameters of low-voltage switching devices of Russian production – magnetic starters PML and switches RE19 has been carried out. The problem of evaluating energy efficiency of operation of magnetic starters and switches installed in in-plant power supply systems has been presented. The main destabilizing factors significantl...

Research activities in the field of development of electrical power and electrical equipment include the development of new approaches to assessing the reliability indicators of electrical equipment elements and in-house power supply systems in general. The study has examined methods for assessing the reliability of electrical equipment in intra-sh...

The section describes methodical approaches to construction of short-term forecasts of fuel and energy balances for six groups of fuels (coal, gas, oil products, biofuels, electricity, thermal energy). THE PURPOSE of the article is to develop a methodology for researching a forecast of fuel energy balances, to analyze the dynamics and experience of...

While the adoption of electric vehicles is accelerating in an unprecedented way, the lack of infrastructure for charging them hinders the development of this market. To compensate for these shortcomings, mobile charging stations that can provide charging services without restrictions on the place and time of the charging process could play a signif...

Valtchev S., Yousef Ibragim. Исследование вероятностных характеристик надежности электрооборудования внутрицеховых систем электроснабжения // Вестник Казанского государственного энергетического университета.

Abstract—This paper proposes a universal method for improving the dynamic characteristics of induction motors. The transient processes here fluctuate greatly, which reduces the energy efficiency of the electromechanical converter. A flexible feedback on flux linkage is proposed, which makes it possible to suppress oscillations. A numerical experime...

Abstract—This article is devoted to the application of previously developed algorithms and models to the problems of managing the microclimate of the cement clinker burning shop of a cement enterprise. Based on experimental data, the coefficients of the basic general model of the filter and thermal control were obtained. The adequacy of the constru...

Abstract—The paper studies the technical parameters of low-voltage switching devices. The main factors influencing the technical characteristics of devices are given. The dependence of the contact heating temperature of the apparatus on the loading factor is revealed. It is proved that with the increase of loading of devices the temperature of heat...

The paper reflects the problem of evaluating the efficiency of low-voltage switching devices, which are used in the systems of in-plant power supply. The technical condition of circuit breakers and contactors of different manufacturing plants has been investigated, models for determining the technical characteristics of switching devices have been...

Abstract — The article describes the method of controlling the electric drive of the electromechanical looper (loop holder) at the moment the strip enters the gap of the finishing group of the hot rolling mill. An automatic strip tension control system with an indirect control principle is considered. The results of mathematical modeling of the ele...

Power transformers are one of the main components of power supply systems needed to reliably supply electricity to consumers. As we know, the value of the allowable load of transformers is determined by the value of the allowable heating of structural elements, on which the service life of transformer period depends. Reliable data on the technical...

The article discusses the main features of mechanical, chemical, thermal, and electrical processes occurring in the contact zones of the surfaces of contact connections of electrical devices. The parameters determining the value of power losses and power consumption in low voltage switching equipment are analyzed. The main features of the character...

Abstract: The stability and reliability of electrical equipment depends first on its technical resource. One of the main reasons affecting the technical resource of the electrical equipment of large irrigation pumping stations of the first lift is the starting transient modes of pumping units. The study of methods to increase the technical resource...

In this article, a study of radial and trunk circuits of networks was carried out and power losses were determined using the proposed coefficients. Equivalent resistances of the investigated circuits were calculated considering the changes in circuit and mode parameters. Results of calculations are presented, considering equipment layout and techni...

Abstract—The article describes the reliability of transformers, the failure rate and uptime to the first failure, the durability and maintainability of transformers and their service life, the allowable temperature rises and the dependence of steady-state overheating on the load factor of the transformer. An assessment of the effect of ambient temp...

Abstract— The article is dedicated to the problems that arise during the operation of individual heating points associated with the frequent failure of control valves. An individual heating point is a component of a district heating system that connects the main network with the building's own heating system. At the initial stage, a mathematical mo...

Abstract — The article studies the dependence of active power losses in contacts and contact systems of circuit breakers, contactors, and magnetic starters from the main parameters of electrical equipment. Models of functional dependencies of active power losses on nominal current for low voltage switching devices of some manufacturers were develop...

Abstract – Industrial power supply facilities have in their composition technological cycles of varying degrees of complexity and the corresponding electrical equipment of intrashop power supply systems. The aim of the study: to determine laws of change in probabilistic reliability characteristics of low-voltage electrical equipment, namely circuit...

Abstract—In this paper, a focus on the Dynamic Inductive Power Transfer (DIPT) systems is made, and two alternative configurations are presented and discussed from both an economic and technical point of view. In particular, the possibility of using a multiple receiver is analyzed. As result, it has been seen that the increase in the number of rece...

RELEVANCE. Any device loses its performance over time, Power transformers too. The problems of overheating and insulation are the main influencing factors to the operation status of power transformers. Thus, the study is of high relevance and applied demand, because the heating ofpower transformer elements, especially in the territory of the Syrian...

Citation: Valtchev, S.; Meshcheryakov, V.; Gracheva, E.; Sinyukov, A.; Sinyukova, T. Abstract: Energy saving issues occupy a leading position in all control systems. This article provides a detailed analysis of control systems and is conducted by considering the complexity of implementation and response to the control action. The implementation of...

THE PURPOSE. The study is devoted to the problems of ensuring the smooth start and stop of lifting and transport mechanisms. Standard regulators do not allow you to achieve the desired results with changing indicators, the exact values of which are not always available for measurement. Control signals, in such systems, usually correspond to data fr...

THE PURPOSE. Conduct a study to improve the reliability of forecasting the magnitude of power consumption and power losses at an industrial enterprise. METHODS. Methods are used to determine and predict the parameters of consumption and losses of electricity at industrial facilities. RESULTS. To clarify the magnitude of electricity losses, it is pr...

In this paper, a Dynamic Resonant Inductive Power Transfer (DRIPT) System for the Electric Vehicle (EV) battery charging is proposed. In particular, the aim of the work is the general design of the whole system and its validation, with particular attention to the power electronic converters and their control. For the transmitter side, a DC/AC conve...

Abstract—It is being estimated how asymmetry of the current load in the phases of the power lines influences on the magnitude of the absolute and relative losses of electrical energy in distribution grids with a voltage of 0.4-20 kV Methods for load balancing in the phases of power lines and reducing the component of electrical energy losses from a...

Abstract—The article discusses the problems of increasing the reliability of 110 kV overhead power lines in a sharply continental climate, the law of distribution of failures of overhead lines operating in specific conditions is determined. Issues of increasing the reliability of overhead power lines in the Sughd region were considered. The main fa...

The world is once again facing massive energy- and environmental challenges, caused by global warming. This time, the situation is complicated by the increase in energy demand after the pandemic years, and the dramatic lack of basic energy supply. The purely “green” energy is still not ready to substitute the fossil energy, but this year the fossil...

THE PURPOSE. Investigation of the control system of the cargo movement mechanism when using different variants of sensorless control. The search for the optimal option, in which the formation of the speed is identical to the data obtained from the speed sensor. Analysis of the results obtained during the study, including the results obtained taking...

A generalized non-affine nonlinear power system model is presented for a single machine bus power system with a Static Var Compensator (SVC) or State Var System (SVS) for hybrid Unmanned Aerial Vehicles (UAVs). The model is constructed by differential algebraic equations on the MATLAB-Simulink platform with the programming technique of its S-Functi...

1 Худжандский политехнический институт таджикского технического Университета имени академика М.С. Осими, г. Худжанд, Таджикистан 2 Казанский государственный энергетический университет, Россия 3 Новый Лиссабонский университет; ТУ София и БФУ Болгария ORCID*: http://orcid.org/0000-0002-2573-759X, shahbozdadoboev@mail.ru Резюме: ЦЕЛЬ. Анализ пусковых...

THE PURPOSE. Investigation of the degree of influence of the characteristics of inplant electrical networks on the reliability of the results in the algorithms for estimating equivalent resistances. METHODS. When solving this problem, a study of the radial power supply scheme of the tool shop section was carried out with the calculation and modelin...

In recent years, the growing concern for air quality has led to the development of sustainable vehicles to replace conventional internal combustion engine (ICE) vehicles. Currently, the most widespread technology in Europe and Portugal is that of Battery Electric Vehicles (BEV) or plug-in HEV (PHEV) electric cars, but hydrogen-based transport has a...

THE PURPOSE. Investigation of the degree of influence of the characteristics of in- plant electrical networks on the reliability of the results in the algorithms for estimating equivalent resistances. METHODS. When solving this problem, a study of the radial power supply scheme of the tool shop section was carried out with the calculation and model...

ТНE PURPOSE. The objective of this study is to investigate the possibilities of longer distance resonant energy transmission applying Wireless Power Transfer (WPT) in the MHz frequency range. The planned final purpose is the energy to be transferred to all types (aerial and terrestrial) of electric vehicles (EV), mainly for the battery charging at...

THE PURPOSE. Investigation of the degree of influence of the characteristics of inplant electrical networks on the reliability of the results in the algorithms for estimating equivalent resistances. METHODS. When solving this problem, a study of the radial power supply scheme of the tool shop section was carried out with the calculation and modelin...

THE PURPOSE. In controlled AC drives used on continuous-action mechanisms, which include conveyors, conveyors, cranes, the most widespread are asynchronous motors with a phase rotor, controlled mainly along the rotor circuit using various regulators with low energy efficiency. To improve the energy efficiency of an electric drive based on ADFR, it...

THE PURPOSE. In controlled AC drives used on continuous-action mechanisms, which include conveyors, conveyors, cranes, the most widespread are asynchronous motors with a phase rotor, controlled mainly along the rotor circuit using various regulators with low energy efficiency. To improve the energy efficiency of an electric drive based on ADFR, it...

The hybrid three-phase rectifiers (HTR) consist of parallel associations of two rectifiers (rectifier 1 and rectifier 2), each one of them with a distinct operation, while the sum of their input currents forms a sinusoidal or multilevel waveform. In general, rectifier 1 is a GRAETZ (full bridge) (can be combined with a BOOST converter) and rectifie...

This work presents a mid-range wireless power transfer (WPT) system that uses a high-temperature superconducting coil in the transmitter circuit to increase the efficiency of the system. The presented system is foreseen to provide energy to superconducting magnetic levitation vehicles and is intended to be implemented in the Brazilian MagLev-Cobra....

ЦЕЛЬ. Практическая реализация плазменной установки с полой цилиндрической камерой и исследование возможности стабилизации и регулирования положения электрической дуги и выхода языка плазмы из рабочей камеры на заданное pасстояние. Проанализировать особенности конструкций электроплазменных установок (плазмотронов), предназначенных для выполнения раз...

Superconductivity is a remarkable state of matter exhibited by some materials, which is characterized by the vanishing of electrical resistivity at cryogenic temperatures, among other phenomena. However, the prospective economical viability of superconducting devices relies heavily on an efficient cooling system to remove the heat generated during...

THE PURPOSE. In controlled AC drives used on continuous-action mechanisms, which include conveyors, conveyors, cranes, the most widespread are asynchronous motors with a phase rotor, controlled mainly along the rotor circuit using various regulators with low energy efficiency. To improve the energy efficiency of an electric drive based on ADFR, it...

It is inevitable that high-intensity, wide-spectrum electromagnetic emissions are generated by the power electronic equipment of the Extra High Voltage (EHV) power converter station. The surveillance flight of Unmanned Aerial Vehicles (UAVs) is thus, situated in a complex electromagnetic environment. The ubiquitous electromagnetic interference dema...

The paper reports a theoretical and experimental study of a novel thermal energy harvester with heat-induced vibrations in an environment with a nonzero temperature gradient. The energy harvester comprises a Shape Memory Alloy wire from Nitinol and two elastic cantilever beams with deposited Lead Zirconium Titanate piezoelectric layers. The Shape M...

The IEEE IES: An Interdisciplinary Family of Mentors, Young Professionals, and Students If we look at the world today, we may wonder how technology is important for us. Is there any discipline that could cover and join with current trends? At the IEEE Industrial Electronics Society (IES) website [1], one can read the following: The Industrial Ele...

If we look at the world today, we may wonder how technology is important for us. Is there any discipline that could cover and join with current trends? At the IEEE Industrial Electronics Society (IES) website [1], one can read the following: The Industrial Electronics Society through its members encompasses a diverse range of technical activities d...

In this paper, a new way to mitigate the current interactions is proposed. The problem of current interactions arises when a modular three-phase (3-phase) rectifier (three single-phase modules) with boost converter for power factor correction (PFC) is used. A new differential-mode choke filter is implemented in the developed boost converter. The ch...

THE PURPOSE. To analyze the starting transient processes of an asynchronous motor with a low quality of electricity in the supply network. To consider starting an asynchronous motor at a reduced mains voltage, at a reduced mains frequency, as well as starting with voltage dips in the network. METHODS. Simulation modeling based on computer models wa...

In this paper, an analytical formula for the coupling coefficient (k) was introduced for two inductively coupled coils of ring configuration. The response surface methodology (RSM) was used as a tool to develop this formula. The k was tested as a function of the geometrical parameters which include the followings parameters: an air-gap (d) between...

This study introduces an efficient method to determine the computation mathematical formula of mutual inductance (M) for a pair of ring coils. A design technique called Box-Behnken that based on the response surface methodology (RSM) was utilised to develop such a formula. The M was developed to be a function for the air-gap (d) between the coupled...

The restoration of the materials surface layer can be performed by depositing a metal layer using an electric arc plasmatron. The restoration technology is based on feeding molten metal into the reduction zone, and subsequent additional heating of the reduction zone by plasma. In an electric arc plasmatron, an electric arc is ignited between two el...

This paper discusses the improvement of two-phase motor control systems. In the last 100 years two-phase induction motors have been massively replaced by the three-phase motors, but nevertheless in many industries, they are still good solution. These areas are high-power traction drives with DC motors used in electric vehicles. Or vice versa, low-p...

Real-time systems are confidently used by electric drive developers to test control systems and converters. Such systems are called Hardware-in-the-Loop (HiL) system and Power Hardware-in-the-Loop (PHiL) system. The application options of these systems are presented. Issues connected with HiL and PHiL requiring study and research are discussed.

In this paper, an analytical formula for the coupling coefficient (k) was introduced for two inductively coupled coils of ring configuration. The response surface methodology (RSM) was used as a tool to develop this formula. The k was tested as a function of the geometrical parameters which include the followings parameters: an air-gap (d) between...

Cardiovascular diseases remain the leading cause of morbidity, mortality, early disability and growing health costs worldwide. The difficulty for monitoring the evolution of cardiovascular related diseases can be, partially, attributed to the lack of appropriate indicators for arterial injury and cardiac disfunction during routine clinical practice...