POWER ENGINEERING: economics, technique, ecology

OPTIMIZATION OF POWER LOAD FOLLOWING MODES FOR VVER-1000

2024-11-04T12:26:10+02:00

The need to involve nuclear power plants in daily power regulation is driven by the gradual increase in the share of renewable energy sources in the Unified Energy System (UES) of Ukraine. Additionally, the conditions for implementing measures to address climate change and deteriorating operating conditions of the UES in the face of economic changes play a significant role. There is an increased demand for maneuverable capacity to ensure the fulfillment of the daily electricity consumption schedule. However, the existing daily power regulation mode for PWR-1000 in Ukraine has significant drawbacks.

Therefore, this paper proposes a method for optimizing the daily power regulation mode, examines the shortcomings of the existing power regulation method at nuclear power plants with PWR-1000 reactors in Ukraine, and suggests an approach for their elimination — utilizing the so-called "grey" rod clusters for power load following in this mode.

DEVELOPMENT OF ARTIFICIAL INTELLIGENCE MODEL IN THE FIELD OF ATOMIC ENERGY AS A TOOL OF SUPPORT IN DECISION-MAKING

2024-11-05T09:37:15+02:00

This article focuses on developing and applying an artificial intelligence (AI) model in the field of nuclear energy, emphasizing its importance as a decision-making support tool. The current state of AI in nuclear energy is discussed, with a special focus on the creation of a proprietary classification model.

The article outlines the main stages of AI model development and its practical application for classifying events at nuclear power plants. It utilizes machine learning technology and natural language processing to develop the model. The significance and innovative approach of using AI in nuclear energy are emphasized, considering its potential in enhancing the efficiency of processes at nuclear power plants.

Results demonstrate the high efficiency (accuracy) of the developed AI model during testing for event classification. The current era of digital transformation and rapid technological development highlights the increasing importance of AI as a tool in various sectors.

Additionally, the article covers the international promotion of AI in nuclear energy, particularly by the International Atomic Energy Agency (IAEA) and the United States Nuclear Regulatory Commission (NRC). It details the efforts of these organizations in exploring the application of AI technology in nuclear technologies and regulatory activities, emphasizing safe AI use and developing strategic plans for AI applications.

In conclusion, the article suggests the model's potential application in investigating nuclear power plant events, that can be used for classifying by categories, root causes, corrective actions etc. The article concludes that while AI is a modern technology finding application in various fields including nuclear energy, it cannot fully replace human involvement in the nuclear sector. However, AI combination with human input can improve the efficiency and safety of processes at nuclear power plants.

USE OF THE THEORY OF FINITE AUTOMATA FOR SUPERVISION OF THE OPERATION OF THE COMPRESSOR UNIT

2024-11-05T09:45:59+02:00

The purpose of the publication is to develop a methodology for presenting switchgear cabinets with a voltage of 6 (10) kV in the form of a state machine. The complete distribution device is one of the most responsible electrical devices of medium voltage. Their reliable operation ensures uninterrupted power supply to industry, administrative and household premises, and agriculture. It has been proven that the principle of operation of switchgear cabinets is similar to a deterministic finite state machine. The theory of finite automata and graphs is applied for the analysis of the operation of the cabinet of a complete switchgear. It is shown that the theory of finite state machines allows combining all possible modes of operation of switchgear cabinets. Representation of the switchgear cabinet model in the form of a deterministic finite state machine allows designing a cabinet with the necessary features. A 6 (10) kV switch cabinet state transition diagram has been developed. Such a diagram can be useful for understanding the operation of the cabinet of a complete switchgear, improving the qualifications of electrical personnel.

A complete description of the operation of the cabinet using morphological phrases is given on the example of the K-XII type switchgear cabinet with the VMP-10K circuit breaker (SD-300 kW connection). It was concluded that any switching device with a voltage up to and above 1000 V can be represented as a finite state machine. In addition to the diagram of state transitions, the operation of switching devices should be explained using morphological phrases (IF, AND, OR, THEN, NOT POSSIBLE).

SPECIFIC OF THERMOHYDRAULIC CALCULATIONS OF CORE PRESSURIZED WATER SMALL MODULAR REACTORS IN CASE NATURAL CIRCULATION OF THE COOLANT

2024-11-05T09:55:38+02:00

The article has been devoted to the study of the main features of pressurized water small modular reactors and an analysis of the influence of the specified features on the thermohydraulic calculation of the core.

Special attention is given to small modular reactors with natural circulation of the coolant. It was determined that in the calculation of the core, natural circulation affects the determination of pressure losses and the heat transfer coefficient. When determining pressure losses, the difference between natural and forced coolant circulation lies in the components of pressure losses that need to be considered. In the determination of the heat transfer coefficient, the key factor is the determination of the Nusselt number, where the circulation flow regime affects determining criteria. The issue of determining the critical heat flow using the CHF LOOK UP TABLET method is also considered for the further determination of the departure from nuclear boiling, which serves to assess the safety of operation of the installation.

As an example, during the study, a thermohydraulic calculation of the core of the small modular reactor Holtec SMR-160, as one of the advanced representatives of this type of reactor, was performed. As a result of the conducted calculation, the value of pressure losses, the distribution of the heat transfer coefficient and the minimum departure from nuclear boiling were obtained. The study shows the departure from nuclear boiling obtained as a result of the calculation is close to the minimum allowable value, but it is quite acceptable considering the characteristics of natural coolant circulation. However, it necessitates further analysis during the assessment of the reactor facility's safety.

RESEARCH OF IMPULSE OVERVOLTAGES IN HIGH VOLTAGE CABLE LINES WITH CROSS BONDING CABLE SHEATH

2024-11-05T10:03:54+02:00

In the paper, a mathematical model of a power transmission cable line with cross bonding of screens is developed for the study and analysis of wave processes of overvoltage pulses during the cross bonding of screen contours. Equivalent and calculation schemes for the cross bonding of cable line shields are proposed, for which analytical expressions for calculating overvoltage maxima are obtained. Based on the analysis of the wave processes occurring in cross bonding cable shields of the three-phase system, it was established that when estimating the maximum voltage on the shields of the cable line, it is permissible not to take into account the waves reflected from the nodes located behind the node under consideration in the direction of wave travel. On the contrary, it is recommended to take into account the mutual influence of the phases, if we approximately accept the wave resistance of the screen-earth channel, which is equal to the wave resistance of the inter-screen channel. It has been established that taking into account the mutual influence of the phases leads to a decrease in the amplitude of the pulse and a reduction in the time of its influence, therefore, in order to calculate the overvoltage maxima, it is necessary to take into account the mutual influence between the screen-screen channels of neighboring phases.

MODERNIZATION OF SCHEDULED MAINTENANCE STRATEGIES FOR ACTIVE SAFETY SYSTEMS OF NUCLEAR POWER PLANTS WITH VVER

2024-11-05T10:27:15+02:00

The strategies for scheduled tests and repairs of active safety systems (with pumps) established by the technological regulations for safe operation of VVER NPP do not take into account many years of operating experience and the results of numerous tests of active safety systems, current reliability indicators and residual life of the main equipment, and other factors. The modernization/improvement of design strategies for scheduled maintenance and testing of active safety systems determines the need to develop appropriate methods for qualifying (justifying) modernized strategies. The paper presents a risk-based method for qualifying modernization of strategies for scheduled maintenance of active safety systems, which takes into account the experience of operation, scheduled maintenance and testing, as well as the current reliability of the main equipment. The developed method is based on the following provisions. The determining reliability indicator for qualifying strategies for scheduled maintenance of active safety systems is the safety function unavailability factor, which determines the probability of a critical failure at the current time depending on the parameter of the intensity of the critical failure flow established in scheduled tests/repairs over the past service life. A critical failure here means a failure to perform safety functions (e.g., failure to turn on a pump, forced pump shutdown due to a violation of performance conditions, leaks in the circuits of active safety systems, etc.) The qualification criterion for the modernization of active safety systems outage strategies is a target risk function that determines the ratio of the coefficients of unreadiness to perform safety functions of the design and modernized active safety systems outage strategies. The conditions for successful qualification are that the unavailability rate of the safety functions of the modernized scheduled maintenance strategy is not greater than the unavailability rate of the design scheduled maintenance strategy. Based on the developed method, the modernized strategy of scheduled repairs of the active part of the emergency core cooling systems of the VVER-1000 reactor is substantiated, and the limitations of the applicability of the modernized strategy are determined.

POWER SUPPLY OF THE COMPLEX OF ENGINEERING AND TECHNICAL MEANS OF THE PHYSICAL PROTECTION SYSTEM IN CONDITIONS OF LONG-TERM POWER OUTAGES

2024-11-05T10:56:21+02:00

Physical security systems in today's conditions play a key role in maintaining nuclear security and ensuring the normal functioning of facilities in the nuclear power industry. Given the possible lack of electrical power caused by missile strikes in wartime, the enemy or criminals can take advantage of the vulnerability of the physical protection system, the means of which will be de-energized, which can lead to unacceptable radiation consequences [1] as a result of successfully executed illegal actions (sabotage, theft, etc.) ).

Therefore, in accordance with the legislation, a number of requirements are put forward to the power supplies of the complex of engineering and technical means of the physical security system, the fulfillment of which in the process of designing, construction or operation of the physical security system is aimed at preventing the failure of power supplies or minimizing the probability of failures in the reliable power supply of the equipment of the physical security n system protection

An important stage of ensuring the uninterrupted functioning of the physical security system in conditions of long-term emergency power outages is the selection of a generator set.

In this work, the object of research is the security of critical infrastructure objects in conditions of long-term power outages, and the subject of research is the power supply system of the complex of engineering and technical means of the physical security system. The paper analyzes the existing regulatory and legal documentation regarding physical security and provides the method of selecting a generator set, as well as the option of integrating the set into the scheme of power supplies of the complex of engineering and technical means. The main method of the process of selecting the specified equipment is the comparison and analysis of the parameters specified by the manufacturer with the parameters and characteristics that will meet the requirements of the current regulatory and legal documentation and the needs of the training center in supplying electricity to this or that equipment. The method presented in the paper is universal in application and can be scaled to other critical infrastructure facilities, where it is necessary to provide power supplies with a power reserve in conditions of long-term emergency shutdowns of industrial power sources.

HEAT EXCHANGE IN THE HEATING ZONE OF ALUMINUM GROOVED HEAT PIPES

2024-11-05T11:09:05+02:00

At the present time, autonomous closed two-phase heat transfer systems - heat pipes (TT) are increasingly used in the systems for ensuring the thermal regimes of some space and ground vehicles. When developing and using such devices, it is necessary to solve the issue of optimizing the characteristics of these systems, which is most realistic to do on the basis of experiments conducted in working conditions. One of the important characteristics is the intensity of heat exchange in the heating zone of the heat pipe during its operation. The article presents the results of experimental studies of heat transfer in the heating zone for different working fluids on the internal developed surface in the form of an Ω-shaped capillary structure of an aluminum heat pipe operating in thermosiphon mode, i.e. the pipe was located vertically, the heating zone was located below. The experiments were carried out on experimental samples of aluminum heat pipes in the range of supplied heat fluxes from 0.1·104 W/m2 to 1.4·104 W/m2 and temperatures of the saturated steam of the working fluid from +30°C to +90°C. The research results are compared with the literature data on the heat exchange of these investigated working fluids on smooth surfaces in conditions of a large volume, and the criterion dependence of the calculation of the intensity of heat exchange for these conditions is obtained.

MODEL OF AN ENERGY-EFFICIENT POWER GRID OF AN INDUSTRIAL ENTERPRISE WITH DISTRIBUTED GENERATION

2024-11-05T11:20:13+02:00

The integration of distributed energy sources into the power grids of industrial enterprises and the development of sustainable energy, which involves the use of low-capacity power facilities, require corresponding changes in the structure of the centralized power supply system. The use of distributed generation increases the reliability of electricity supply to consumers, simplifies the transmission and distribution of electricity between them. However, at the same time, unstable power generation by renewable energy sources can cause unwanted energy flows and additional power losses.

The article proposes a model of an industrial enterprise power grid consisting of three local grids: high-quality and low-quality AC power and the DC grid that unites them. Such a scheme fully meets the requirements for the above-mentioned local modules, significantly simplifies the integration of renewable energy sources into it, makes it unnecessary to ensure the quality of the entire volume of consumed electricity, the electromagnetic compatibility of loads and the grid itself with the distribution one, and significantly reduces the number and total power of power electronics devices used. The described structure of the power grid will also create an effective unified system for managing the process of electricity consumption at the enterprise, into which modern communication technologies of the Smart Grid can be integrated.

To study the proposed power grid by computational methods, a mathematical model is synthesized and its use is considered on the example of a simulated industrial enterprise. The developed mathematical model allows to calculate the steady-state modes of operation of local power grids, taking into account possible places of connection of energy storage devices, sources of distributed generation, etc. The proposed approach makes it possible to choose the optimal variant of connecting distributed generation to the enterprise's power grids, to eliminate unwanted power flows and reduce energy losses in them.

ANALYSIS OF MICROGRID MANAGEMENT MODELS IN THE NATIONAL LEGISLATIVE AND REGULATORY SPACE

2024-11-05T11:38:06+02:00

The article examines the concept of "microgrid", microgrid models and microgrid classification. According to the results of the elaboration of the regulatory legal acts of EU and Ukraine, definitions and classification features of microgrid are proposed, which allow to identify individual models of microgrids. According to the results of the analysis, gaps in the legislation that restrain the development of microgrids have been identified.. References 25. Figures 6.

FEATURES OF VOLTAGE CONTROL IN ELECTRICAL ENERGY DISTRIBUTION SYSTEMS WITH LOCAL ENERGY SOURCES

2024-11-05T11:48:02+02:00

The article deals with the identification and justification of the most rational approaches and technical solutions for voltage control in electrical distribution systems with the local non-dispatchable and dispatchable energy sources in their structure. It has been demonstrated that under conditions in many cases the use of traditional methods of determining the parameters of technical means to realise centralized voltage control using distribution transformers and transformers of power substations not only does not allow to ensure permissible voltage deviations for consumers, but even will deteriorate the quality of electric energy. This is especially true to the situation when the local energy sources are concentrated in separate distribution feeders. In this regard, the paper proposes a modified algorithm for determining the law of voltage control applied to transformer of power substations, demonstrates the possibility and effectiveness of a targeted impact on voltage regimes due to a forced change of the active and reactive power flow in separate feeders with local energy sources. For this purpose, it is planned to use energy storage devices and alternative energy sources that are connected to the network through the inverter interface. Due to the use of the reactive power sensitivity matrix, it becomes possible to determine the most appropriate network nodes, in which alterations in reactive power will be the most effective from the point of view of impact on the voltage levels. Under these conditions, in many cases, by the alteration of load flow in the feeder with local energy sources, it is possible to increase the homogeneity of the load curves of all distribution feeders and, due to this, to improve the efficiency of voltage control without involving investments in the installation of additional voltage control equipment.

ANALYSIS OF THE OPERATION MODE OF THE SOLAR POWER PLANT

2024-11-05T12:01:08+02:00

The article examines the load change schedule of the solar power plant in the Ukraine-Moldova energy union. The analysis of data averaged at minute and 15-minute intervals in the period from 01.10.2022 00:00 to 27.09.2023 14:00 was carried out. Changes to forecasting load changes at solar power plants in the short term are proposed.

Background. The increase in the share of solar electricity generation in the energy systems of the countries of the world leads to the need to control and manage the process of electricity production to increase the stability and sustainability of the energy system. A significant price for compensation of imbalances in the energy system is included in the tariffs, which affects the end consumers of electricity.

Objective: increasing the adequacy of the results of the distribution of deficit frequency containment reserves, frequency restoration reserves to compensate for imbalances that arise when generation is changed at solar power plants. Reducing the cost of compensation for imbalances that occur when changing generation at solar power plants. To solve the goal, it is necessary to analyze the mode of operation of the solar power plant and the amount of imbalances caused by the deviation from the generation schedule at the solar power plant and to develop new methods of short-term forecasting.

Methods: the social engineering approach of forecasting and modeling was used to analyze the processes affecting the method of controlling the generation schedule of the solar power plant.

Results. A new mathematical and technical solution is proposed for compensating the imbalance in the power system in case of a rapid change in the electricity generation schedule at solar power plants. For the first time, the electricity generation schedule at the solar power plant was analyzed and the rate of change of generation at different time intervals was determined. The electricity generation schedule at the solar power plant was analyzed and a new technical solution for forecasting and management of the generation schedule was proposed to be transferred to a higher level than the station one. Such a technical and mathematical solution can be widely used in the process of managing the schedule of electricity generation at solar power plants in many system operators in different countries of the world, where there is a problem of insufficient reserves for frequency support and restoration, and the amount of solar electricity generation has a significant share in the total amount of generation electrical energy.

Conclusions. Data on electricity generation at the B. solar power plant in the period from 01.10.2022 00:00 to 27.09.2023 14:00 were analyzed. According to the results of the analysis of the electricity generation schedule at the B. solar power plant, it is clear that the solar plants are not able to participate in the auxiliary services market because they do not meet the requirements of the transmission system code. A significant problem of solar power plants remains the instantaneous change in the value of electric energy generation, which at peak times reaches 84.377%/min of the maximum value of generation for the studied time period. It is possible to compensate for such imbalances by installing a ESS, but taking into account the specifics of the operation of the solar power plant, it can be concluded that a large-capacity ESS will be needed. Large-capacity ESS will significantly increase the cost and payback period of the solar power plant and will probably be unprofitable for the enterprise. As a result, it is proposed to move the process of generation schedule forecasting and management to a higher level than the station level.

EVALUATION OF COMPLEX INDICATORS FOR FORECASTING THE STRATEGIC DEVELOPMENT OF RENEWABLE ENERGY SOURCES OF UKRAINE WITHIN THE STRUCTURE OF RENEWABLE NATIONAL ENERGY INDUSTRY OF UKRAINE

2024-11-05T12:15:57+02:00

The article is devoted to a systematic review of modern trends in the use of renewable energy sources and their impact on the country's energy system. The basis of the analysis is the assessment of the degree of technological maturity of renewable energy technologies, the effectiveness of their implementation in comparison with traditional energy sources. Thanks to a wide range of analysis, the article makes an important contribution to understanding the prospects and determinants of effective implementation of renewable national energy in the context of modern energy challenges and can serve as a basis for further research in this field.

In this article, the Holt method was chosen as the main method for forecasting - to build forecast models for four key components of renewable energy sources (RES) in Ukraine - wind, solar, hydropower and biomass. Based on the forecasting results, the authors determined the prospects for the development of renewable national energy in Ukraine. The obtained results emphasize the strategic importance of intensifying efforts in the field of development, attracting investments and revising the energy policy with the aim of aligning it with global trends towards a carbon-neutral economy. Appropriate recommendations have been developed regarding the revision of the Energy Strategy of Ukraine and the optimization of the legal framework for effective supervision of the proper condition of all generating capacities of the energy system. In the light of these forecasts, the article emphasizes the need for proactive measures to ensure the sustainable and growth of the ecologically clean strategic sector - renewable national energy of Ukraine.

SUBSTANTIATION OF THE POTENTIAL FOR OBTAINING COMPOSITE MOTOR FUEL FROM VEGETABLE OIL AND LIVESTOCK PRODUCTION WASTES

2024-11-05T13:04:15+02:00

Food waste has a negative impact on the environment if it is not handled properly. When organic waste decomposes, it releases methane, a greenhouse gas that contributes to climate change. However, proper management and disposal of food waste can significantly reduce its negative impact. On the other hand, Ukraine has an unresolved issue of high waste intensity. Industrial and household waste is often not properly sorted and recycled, leading to its accumulation in landfills and dumps. Another painful issue is Ukraine's fuel dependence on European countries. Therefore, the production of domestic alternative motor fuels is a promising way to increase fuel independence. The latter can be produced from food waste, thus solving both the issue of waste intensity and fuel dependence.

Therefore, the purpose of this study is to determine the potential for obtaining domestic alternative fuels from food waste. The object of the study is food waste generated in the course of the restaurant business, vegetable oil production and livestock farming in Ukraine. The subject of the study is the methods and technologies for converting food waste into composite motor fuel and their potential to reduce the environmental burden and increase Ukraine's fuel independence. The working hypothesis of the study is that the establishment of an ecological system for the collection and conversion of these wastes can partially resolve the energy situation in the country.

This article describes the harm that food waste can cause to the environment, analyses the global experience of recycling this waste, analyses the largest restaurant chains, analyses waste from vegetable oil production and livestock production in recent years, analyses the conversion factors of food waste into composite motor fuels, and calculates the potential for producing alternative fuels from food waste for Ukraine.

The study found that the average annual potential for alternative fuel production from oil and vegetable raw material waste is in the range of 33.25-44.2 thousand tonnes/year, and the average annual potential for alternative fuel production from animal waste is in the range of 2.65-5.2 thousand tonnes/year. The volume of fuel production from restaurant waste is potentially much higher. However, access to this data is unfortunately still limited. Thus, the total annual potential for alternative fuel production from oil and vegetable waste, as well as animal products, is in the range of 35.9-49.4 thousand tonnes per year. Our hypothesis is confirmed by the results of these studies.

The research is carried out within the framework of the project "Development of technological solutions for the production of composite motor fuels from secondary raw materials to improve energy security" at the expense of the state budget in accordance with the order of the Ministry of Education and Science of Ukraine No. 1572 of 27.12.2023 "On approval of the list of projects of basic research, applied research, scientific and technical (experimental) developments, executed by higher education institutions and scientific institutions belonging to the Ministry of Education and Science of Ukraine".

OVERVIEW OF THE OPPORTUNITIES OF INDUSTRIAL ENTERPRISE PARTICIPATION IN THE ELECTRICITY MARKET

2024-11-05T13:24:32+02:00

The paper analyzes the electricity market of Ukraine, identifies the main opportunities for the participation of an industrial enterprise in various segments of this market. The types of electricity purchase and sale contracts were analyzed, including the bilateral contract market, the day-ahead market, and the intraday market. The procedure of participation in the balancing market is analyzed. Factors affecting the supply price were analyzed. The direction of future studies of the efficiency of the enterprise's consumption of electric energy is determined, one of which is the creation of a forecasting model that includes the techniques and methods analyzed in this work. The classification of forecasting methods according to quantitative and qualitative approaches is given. Limitations and risks of market segments and their impact on the cost of forecasting "error" are defined. It is proposed to carry out an assessment of the economic efficiency of forecasting methods and models, which will take into account the cost of forecasting "error" as a result of participation in various segments of the electric energy market.

ON SOME PERSPECTIVES OF THE USE OF BIOMASS IN THE DEVELOPMENT OF CENTRALIZED HEAT SUPPLY SYSTEMS

2024-11-05T13:31:22+02:00

As a result of the inconsistent and non-systematic policy regarding the transition of the housing and communal economy of Ukraine, in particular, the field of centralized heat supply, to work in market conditions, significant difficulties have arisen in providing heat to consumers. The untimely development of the regulatory and legal framework for the settlement of these issues led to a poorly predicted policy in the field of heat supply. Excessive liberalization regarding the introduction of individual heat supply in the zone of centralized heat supply led to the "washing out" of the most solvent consumers, significantly complicating the financial situation of heat supply companies. The Government has approved the Concept of the program for the introduction of efficient centralized heat supply in Ukraine, which foresees a significant increase in the share of renewable energy sources, waste heat energy, and the use of cogeneration technologies. The increase in the share of RES in the production of thermal energy is mainly carried out on the basis of the use of biomass. Analysis of the structure of the current consumption of biomass/biofuels in Ukraine shows that the dominant role here belongs to woody biomass, the available potential of which is already used by 90%, and sunflower husks by 83%. Further prospects and opportunities for increasing the volume of energy production from biomass are primarily related to the use of crop production by-products (straw, corn stalks, etc.) and the cultivation of energy crops. Ways to realize this potential should arouse the greatest interest. For this purpose, it is proposed to amend the current legislation regarding the definition of the term "energy plants", to improve the legal basis for the development of farming for the cultivation of energy plants, the conditions for the lease of plots on unproductive and degraded lands. For the further development of market relations in the field of heat supply in Ukraine, it is expedient to develop and adopt the draft Law on the Thermal Energy Market, which should also regulate the conditions for the transition to individual heat supply in the area of centralized heat supply, based on the requirements and experience of the EU.

STUDYING THE REGULARITIES OF THERMAL DECOMPOSITION OF SUNFLOWER HUSK UNDER CONDITIONS OF HIGH-SPEED HEATING

2024-11-05T14:05:00+02:00

Fuel waste from oil extraction plants – sunflower husk – is used to replace organic fuel. The study of the regularities of thermal decomposition of the husk under conditions of high-speed heating in boilers is the aim of this work.

The cellular model of sunflower husk (SH) includes three main components – 30–48% cellulose, 34–38% hemicellulose and 17–26% lignin. Depending on the structure, the elemental composition of the fuel, the quantitative and qualitative composition of volatiles, and, as a result, the calorific value differ. In addition, different molecular structures of individual components lead to different decomposition mechanisms during pyrolysis. Sunflower husk contains 14–18% (by weight) of bound carbon, 70–76% of volatiles, and 5–10% of moisture. The calorific value Q_n^r of the husk ranges from 15–21 MJ/kg.

The thermal decomposition of SH in a fluidised bed at temperatures of 500–1000 °C produces volatiles and solid coke residue (up to 20–30% of the initial mass), which has low reactivity and high strength. To record waste gas yields, an experimental method was used to study the thermal processing of fuel in a laboratory reactor under conditions of high-speed heating in a fluidised bed using a mass spectrometer. Dynamic curves of waste gas yields have two distinctive sections: the first one corresponds to the release and burnout of volatiles, and the second, longer one – to the burnout of coke residue. The second stage determines the completeness of the utilisation of sunflower husk fuel, the design features of the combustion chamber, efficiency and operating parameters of the process. To reduce heat losses due to mechanical underburning, it is recommended to carry out this stage at temperatures above 850–900 ^oC. With an increase in temperature, a decrease in the total duration of husk burnout is observed. An empirical dependence of the burnout time of the husk in the fluidised bed on the temperature T was obtained: t = 3,55·10⁵/Т^1,53±2, s.

DEPENDENCE OF THE VOLTAGE ON THE POWER ELECTRIC DIODES OF THE COMPENSATION CONVERTER ON THE FREQUENCY OF THE TRANSISTOR REVERSALS OF THE COMMUTATING LINK

2024-11-04T11:16:03+02:00

Studies of compensation-type electrical energy converters, conducted both by the authors of the publication and by other scientists, show that their energy characteristics and operating conditions of power equipment depend on commutating voltages. The tested three-phase bridge compensation converter contains one commutating link consisting of a three-phase capacitor battery and a three-phase group of fully controlled devices. The latter are a capacitor bank switch, performing the functions of switching capacitors in such a way as to ensure the energy process of the converter, in which its reactive energy is compensated, or generated, if necessary. At the same time, the operating conditions of the power equipment of the converter also change. The main content of the study is the analysis of the components of the reverse voltage of the power electric diodes of the compensation part of the converter and the dynamics of its change at an increased frequency of control pulses of the transistors of the commutating link. This is required when determining the class of diodes in the case of introducing a converter according to the scheme under study into production. The question of the class of diodves is considered in the context of the energy capabilities of the converter when regulating the operating mode according to the requirements of the technological process. The results of the research relate to the control of transistors of the commutating link by pulses of double, quadruple and eightfold frequency. As a result, relationships were obtained for calculating the maximum instantaneous value of the reverse voltage of electric power diodes in various operating modes of the converter. The ranges of the delay in the moment of supply of control pulses to the transistors of the commutating link are revealed. The generalized conclusion shows that on the electric power diodes of the compensation part of the converter, the reverse voltage does not exceed the voltage on other valves. Refer. 11, fig. 12.

ANALYSIS OF THE FUNCTIONAL CAPABILITIES OF PULSE AC VOLTAGE REGULATORS WITH A COMMON SWITCHING NODE OF VALVE KEYS

2024-11-04T11:26:57+02:00

The article discusses the functional capabilities of pulse voltage converters with a common switching node for multiple circuits that need to be switched. These converters are divided into two groups: those with bridge switches and those with matrix switches. The operation of the common switching node of thyristors in the input bridge of a single-phase voltage regulator is shown as an example.

The analysis of power circuits of both types of single-phase converters showed that using a common switching node provides additional useful properties, such as increasing the speed of voltage regulation with the number of levels greater than the number of thyristor pairs. The presence of a voltage-doubling transformer in the converter structure makes it possible to prevent overvoltage.

It is particularly useful to use a common switching node in single-phase wide-band voltage regulators whose power structure is typically based on transformers that operate at both the main and higher frequencies. Due to the double energy conversion, these devices have an increased number of switched valves, so the common switching node significantly improves their performance and allows for regulating the output voltage using both frequency-pulse and pulse-width methods in the range of 0-1 U_IN with high quality indicators, reversing the output voltage relative to the network voltage, and combining the functions of a modulator (inverter) and a demodulator in one block.

Research on three-phase bridge and matrix converters with a common commutation node has shown that using this power device structure is an effective approach for voltage symmetry when connecting single-phase loads to a three-phase network; for fast switching of backup networks in uninterruptible power supplies; and for direct frequency conversion with the ability to control voltage and reactive power.

ANALYSIS OF PROCESSES IN CONVERTER WITH TWENTY-FIVE-ZONE VOLTAGE REGULATION AND ACTIVE-INDUCTIVE LOAD

2024-11-04T11:41:19+02:00

Analysis of the electromagnetic processes is organized beside this article in electric circuit with semiconductor commutator. Mathematical model is created for analysis electro-magnetic processes in semiconductor converter with width pulsed regulation of the output voltage. The broughted graphs, which reflect the electromagnetic processes in electric circuit. Method much parametric functions was used when performing calculation. The mathematical model of the converter is created for fifteen zoned regulations of the output voltage. Article is devoted to the development of a method of multi-parametric modulating functions by means of working out of new mathematical models and definition of functions and the algorithmic equations for the analysis on sub-system components of electromagnetic processes in electric circuits of variable structure with sinusoidal, direct and pulsing voltage. Introduction of functions with discrete parameters in the algorithmic equations for analysis of processes in circuits with semiconductor commutators simplifies modeling on subsystem components. The mathematical model of steady-state processes and transients in electric circuits of semiconductor converters of modulation type with multi-channel zonal use of phase and line voltages of a three-phase network of power supplies is developed. The mathematical model of electric circuits of thyristor shapers of electro-discharge pulses for the analysis and the matching of capacitors charging modes with decrease several times of electric resistance of technological load is also created. The obtained results have a great value for development theoretical electrical engineering in a direction of simplification of calculations of electromagnetic processes in electric circuits with semi-conductor converters of the electric power. The Electromagnetic processes in electric circuit under width-pulse regulation possible to analyse with use the algorithmic equations multivariable function, which argument are a system parameters semiconductor commutator, signal of control, phases to network of the power supply and time. Introduction multivariable function with discrete parameter in algorithmic equations of the analysis formed and connecting processes in electric circuit of the variable structure allows to reflect change of this structure under system components, simplifying modeling and analysis of such processes to account of the generalization of the got equations. Except specified correlations and diagrams designed model allows to analyse forms of the output voltages and current of the separate power modules.

ANALYTICAL AND STATISTICAL ASSESSMENTS OF THE METHODOLOGY FOR EVALUATING THE QUALITY OF LAMINATED MAGNETIC CORES

2024-11-04T11:57:39+02:00

The paper solves the relevant issue of improving the reliability of electromechanical converters with a steel laminated magnetic core by implementing effective measures to diagnose the quality of the laminated core. A method for assessing the quality of laminated magnetic cores with insulated sheets is proposed. The method is based on the analysis of the response of electromagnetic interconnected circuits to test transient processes in order to assess the development of defects in the inter-sheet insulation and the concentration of parasitic eddy currents associated with specific losses in the magnetic core which is the normative method of magnetic core evaluation that is closest to the operation of an electric machine under real conditions. Taking into account the complexity and labour intensity of regulated methods of core quality control, a reasonable assessment of the relationship between the eddy current time constant and the specific losses in the magnetic circuit will significantly simplify the test methodology, the implementation of which does not require complex and expensive equipment and high qualification of the service personnel. In addition to the physical connection, the paper shows the statistical relationship between the eddy current time constant and the specific losses in a number of real magnetic circuits and performs statistical processing of the experimental data. A linear regression dependence is obtained and the correlation coefficient is estimated, which confirms a significant relationship between the above components on the example of magnetic cores of different geometries. Confidence intervals for defect-free and defective magnetic cores are estimated, taking into account the geometric dimensions, power, and number of poles of the studied electric motors.

DETERMINATION OF THE PARAMETERS OF THE MATHEMATICAL MODEL OF THE WATER SUPPLY SYSTEM OF A HIGH-STORY BUILDING UNDER CHANGES IN THE INLET PRESSURE

2024-11-04T12:21:10+02:00

Prospects for improving the energy and resource efficiency of water supply systems have been studied. The peculiarities of the operation of the water supply system of a multi-story residential building under conditions of increased pressure at the entrance of the water supply system are analyzed.Mathematical and software tools have been developed for the formation of recommendations for the implementation of energy- and resource-saving approaches in the design of water supply systems of multi-story buildings. In order to develop a refined mathematical support for the development of recommendations for improving the energy efficiency of water supply systems, the water consumption calculations of a multi-story building were refined, and the expressions for the distribution of water consumption values by floor were obtained. The use of an indicator of the operating mode of the system is proposed and justified: consumer needs for water as the amount of water consumption at a minimum sufficient input pressure. According to the cyclogram of water consumption by users of the building, the need for water, which is the same for all floors, is determined. A methodology for calculating water consumption by each individual floor based on the experimental results of changes in water consumption of the building with changes in inlet pressure has been developed. The influence of the amount of excess pressure at the entrance of the house on the amount of water consumption by its residents was studied. It has been established that due to excess pressure in the system, for a seven-story building, for same resident's need for water, the difference in consumption between the first floor and the seventh floor can be 9%. The results of flow calculations for zero excess pressure at the water supply system inlet were obtained; the results of flow calculations for excess pressures corresponding to 1, 2, 3 and 4 atm were obtained. For the studied example of a seven-story building, the probable annual increase in water consumption for each of the above-mentioned excess pressures, which are 4718, 9400, 14070 and 18696 m3, respectively, was calculated.