Mode Of Operation Research Articles

Aeroelasticity Analysis of Turbine Blade with Asymmetric Outlet Pressure

Elements of high-power steam turbines are subjected to significant unsteady loads, in particular, rotor blades of the last stages. These loads can, in some cases, cause self-excited oscillations, which are extremely dangerous and have a negative impact on the efficiency and service life of the blade cascade. Therefore, when designing new or modernizing existing steam turbine stages, it is recommended to study the aeroelastic characteristics of the blades. The paper presents the results of numerical analysis of the aeroelastic characteristics of the rotor blade cascade of the last stage of a 380 MW steam turbine, taking into account the asymmetric pressure distribution behind the stage. The pressure distribution is caused by the influence of the exhaust hood and was obtained experimentally. The analysis used a proven numerical method for simultaneously solving the coupled problem of unsteady aerodynamics and elastic oscillations of blades, which allows predicting the amplitude-frequency spectrum of unsteady loads and blade oscillations in a viscous gas flow. The modeling results are presented in the form of displacements of the peripheral blade section and aerodynamic forces acting on this section, as well as their spectra. Also, the dependence of the aeroelasticity coefficient on the inter-blade phase angle of oscillation was obtained. The results of the calculations showed the absence of flutter and self-oscillations according to the first natural form of blade oscillations in the partial mode of operation of a steam turbine. The analysis of the results did not reveal a significant effect of the pressure asymmetry at the outlet of the cascade, due to the significant difference between the excitation frequencies caused by the non-uniformity and the natural frequencies of blade oscillations.

Investigation of the Resource Indicators of the Intermediate Pressure Rotor of the K-200-130 Turbine

The paper is devoted to the study of the medium-pressure rotor of the K-200-130 turbine, which has exhausted its park life of 220 thousand hours and 800 starts, namely, the prediction of the durability of this equipment and the extension of its operation beyond the park life. A geometrical model of the most loaded part of the rotor was developed - from the middle of the shaft neck in the area of the thrust bearing to the 5th stage disc. The main study area was the 13th stage fillet on the 14th stage side. The reason for studying this zone is that it is the most loaded zone according to the authors' experience and similar studies. The analysis of the steel condition showed that when operating in a typical semi-basic operating mode, the accumulated damage in the rotor metal due to cyclic fracture mechanisms is 27 %. The static damage is 49 %. Thus, the total metal damage is 76 %, which sets the residual service life of the medium-pressure rotor of the K-200-130 turbine unit at 63300 hours.

Topology synthesis of coupled inductor based four port DC-DC converter for multi-input PV-battery application with autonomous mode selection

Multiport converters are the most reliable and integral component for latest renewable source integration with multiple inputs. This article is one among the kind, which proposes a novel Coupled Inductor based Four Port topology Multiport Converter (CI-FP-MPC) for integrating multiple PV sources with different voltages. The adoption of coupled inductor contributes an increased voltage gain with reduced stress on the switches and diodes. In addition, reduced number of switches and diodes for a four-port topology provides an increase in efficiency due to its reduced switching and conduction losses. Also, soft switching techniques for zero-voltage-switching in switches and zero-current-switching in diodes transfers a smooth commutation between the mode transients and operating intervals. The proposed converter operates with two PV sources with battery as a source and load as well, paving to two modes of operation viz., TISO and DIDO mode respectively. The proposed topology is derived from the conventional high gain boost converter with an add-on of autonomous sensing and control logic to swap and control between the modes. To evaluate and validate its performance, the converter is developed in experimental setup with a power capability of 750 Watts. The control logic and duty cycle adjustments are supervised in Hardware-In-Loop (HIL) arrangement using dSPACE MicroLabBox. The results show increased efficiency, improved voltage gain and robust mode transition during load perturbations.

An Overview of the Impact of Financial Technology Development on the Real Economy

Financial Technology (FinTech) is leading profound and significant changes in the structure of the global economy at an unprecedented speed with a thunderous momentum. It has subversively reconstructed the operation mode of the traditional financial industry and sown extensive and far-reaching seeds of change in the real economy. This paper aims to comprehensively and deeply scrutinize the multidimensional and omnidirectional impact of FinTech development on the real economy. FinTech has played a vital role in promoting the prosperity of the consumer market, effectively stimulating the vigor of consumption; at the same time, it has opened new channels of financing for small and medium-sized enterprises (SMEs), effectively alleviating the bottleneck of the funding that they have been facing for a long time. In addition, FinTech has significantly improved the overall efficiency of financial services, enabling financial resources to flow more efficiently and conveniently. In optimizing the efficiency of capital and resource allocation, FinTech also shows strong potential to help resources achieve better allocation. More importantly, FinTech has actively stimulated innovation and entrepreneurship, injecting a new powerful impetus for economic development.

МАТЕМАТИЧНА МОДЕЛЬ СИГНАЛУ ІЗ ЗАДАНИМИ ПОЛЯРИЗАЦІЙНИМИ ПАРАМЕТРАМИ В ОРТОГОНАЛЬНОМУ ПОЛЯРИЗАЦІЙНОМУ БАЗИСІ

The experience of combat operations in the context of the large-scale invasion of Ukraine by the russian federation shows that the current level of development of electronic weapons is characterised by a wide variety of types and types of electronic means, the use of multifunctional means with widely variable signal parameters and operating modes. For example, modern (state-of-the-art) ground, air and sea radar stations use deliberate changes in the frequency, time and polarisation parameters of emitted signals in different modes of operation, depending on the tasks and conditions of a complex electronic environment. The presence of differences in the polarisation parameters of signals objectively creates prerequisites for their consideration in processing in order to improve the detection, recognition and direction finding performance of radio monitoring systems in a complex electronic environment. The approach is based on the use of antennas with orthogonal polarisation antenna elements, which allows signals to be represented as polarisation vectors. During the processing, it is necessary to take into account the influence of the polarisation characteristics of the antenna system on the parameters of the polarisation vector (change of the polarisation basis), which is relevant since the signals are received by the antenna system from different angular directions. An important condition for obtaining objective results when studying the efficiency of polarisation processing algorithms is the use of a correct mathematical model of signals with given polarisation parameters in a certain orthogonal polarisation basis, as well as the use of signals from real radio equipment whose polarisation parameters can be determined in a polarisation basis other than the specified one. The article presents a mathematical model that allows expressing the field components through the parameters of the polarisation ellipse, and also gives expressions describing the relationship between polarisation vectors and their covariance matrices in different polarisation bases of the antenna system.

Exploring the Development Model of Senior Care Industry and the Application of Smart Senior Care based on Multi-Country Practices

The purpose of this paper is to explore the development status and practice mode of the global elderly care industry. Through in-depth analysis of the elderly care industry in the United States, Japan, the United Kingdom, Australia, Berlin, Germany, and Singapore, this paper reveals the differences and similarities between the countries in terms of the main body of the elderly care industry, types of services, service modes, operation modes, and typical cases. Meanwhile, this paper also focuses on the application of smart elderly care in different countries, such as the advanced technology support in the United States, the meticulous service in Japan, the community elderly care model in the United Kingdom, the management of nursing homes in Australia, the smart residential system in Berlin, Germany, and the all-round service system in Singapore. By analyzing these practice cases, this paper aims to provide useful reference and inspiration for the development of China's elderly care industry, and to promote the wide application and development of smart elderly care in China. This paper argues that smart aging will become the future development trend of the aging industry, and countries should strengthen exchanges and cooperation to jointly promote the innovation and development of the aging industry.

Steady-State Analysis of Asymmetrical Pulse-Width-Modulated Series Resonant Converter for Light Load Condition

This paper proposes a steady-state analysis of the asymmetrical pulse-width-modulated series resonant converter, commonly employed under light load conditions for effective voltage regulation. The proposed method achieves precise and explicit converter waveforms by applying the Laplace-based theorem to the converter’s ordinary differential equation with periodic and discontinuous inputs, without relying on approximations. By numerically determining the intermediate variables that define converter waveforms, the analysis provides accurate steady-state results based on system parameters. Furthermore, it derives an analytical solution to identify the load conditions suitable for asymmetrical pulse-width modulation operation, as well as the boundary load conditions for discontinuous conduction mode within this mode. The mathematical expressions derived for the converter waveforms and operational modes are validated through simulations using a switching model in PSIM software, as well as through experimental results.

PRÁTICAS DISCURSIVAS ANTIGÊNERO NO INSTAGRAM: UMA ANÁLISE DE COMENTÁRIOS EM POSTAGEM DO SUPREMO TRIBUNAL FEDERAL

In the field of law, LGBTI+ people have experienced several processes of exclusion and stigmatization due to gender identity and sexual orientation, needing to fight numerous disputes within the judiciary to have their rights recognized. At this point, there has been an important role of the Federal Supreme Court (STF) during the last few years. The objective of this essay was to carry out a Critical Discourse Analysis (CDA) based on the social manifestations broadcast on Instagram, see comments related to the publication in celebration of International LGBTQIAPN+ Pride Day made by the Court's official institutional profile in June 2023. It was intended, for this purpose, to have gender studies as a basis not only in the field of elaborations of women's existences, but in the conformation of a system that associates roles, performativities, sexualities and power, that is, an analytical leap to visualize the interferences of gender construction in all the bodies that inhabit this society. The analysis was operationalized by the categories of analysis of representational meaning, based on the linguistic categories of interdiscursivity and the modes of operation of ideology. As a result, we observed that anti-gender discourse is, above all, cisheteronormative and lgbtphobic, positioning people who are part of the LGBTI+ community in invisibility, abjection and exclusion.

СПОСІБ ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ РОБОТИ ТРИФАЗНОГО ГЕНЕРАТОРА ШЛЯХОМ АДАПТИВНОГО ПЕРЕРОЗПОДІЛУ ПОТУЖНОСТІ МІЖ ОДНОФАЗНИМИ СПОЖИВАЧАМИ

The article describes a method of increasing the efficiency of the three-phase generator by applying a system of redistribution of its power between single-phase consumers. Possible approaches and methods for solving the problem of asymmetry of load of power supplies are analyzed. The structural scheme of the power supply system of single-phase consumers is proposed, which realizes a uniform load of phases in the event of load asymmetry. The order of operation of the scheme in different modes of operation of the power redistribution system between consumers is substantiated and on its basis the functioning algorithm is proposed. The substantiation of the circuit solution of the adaptive power redistribution system between single-phase consumers under the control of a single-chip microcontroller is provided and a version of its circuit diagram is developed. The requirements are formulated and on their basis the option of constructing an inverter is designed, which corresponds to the features of the proposed structural scheme according to the level of input voltage. The functioning of the program code of the single-chip microcontroller according to the proposed algorithm has been developed and investigated. The results of practical verification of the functioning of the proposed power supply system are presented, which demonstrated an increase in the efficiency of a three-phase generator by applying a system of redistribution of its power between single-phase consumers. According to the results of the experiment, the directions of further research on the improvement of the proposed scheme are formulated.

Использование энергии рекуперации для обогрева стрелочных переводов от контактной сети постоянного тока с напряжением 3 кВ

Purpose: to create a system for the use of energy recovery on sections of railways electrified with direct current with a voltage of 3 kV. The proposed system should make it possible to use the energy of regenerative braking generated by an electric locomotive or a DC electric train for heating switches during regenerative braking and insufficient power of traction consumers or their absence in the traction network. Methods: analysis of statistical data on the modes of operation of electric rolling stock and traction network, execution of train schedules, analysis and synthesis of circuit solutions, study of domestic and foreign experience in the utilization of energy recovery in railway transport. Results: the principle of using energy recovery, which cannot be used due to the low load in the contact network, for heating switches, increasing the energy efficiency of transportation on electrified rail transport, is proposed. Practical significance: the possibility of using electric energy recovery of electric rolling stock for heating switches in winter is shown, if it is impossible to consume it by other electric locomotives and electric trains. This system can be used in areas electrified with direct current with freight and passenger traffic, which operates electric rolling stock (EPS) with regenerative and regenerative-rheostatic braking.

Design of Multi-Time Programmable Intellectual Property with Built-In Error Correction Code Function Based on Bipolar–CMOS–DMOS Process

The coupling capacitor of the MTP cell used in this paper is an NCAP-type capacitor that has only a source contact, and the layout size of the unit cell is 6.184 μm × 6.295 μm (=38.93 μm2), which is 0.44% smaller than the MTP cell that uses the coupling capacitor of the conventional NMOS transistor type that has both a source contact and a drain contact. In addition, a 4 Kb MTP IP with a built-in ECC function using an extended Hamming code capable of single-error correction and double-error detection was designed for safety considerations. In this paper, a new test algorithm is proposed to test whether the ECC function operates normally in the MTP IP with a built-in ECC function, and it is confirmed through a test using logic tester equipment that the output data DOUT[7:0] and the error flag ERROR_FLAG[1:0] are exactly the same in the cases of no error, a single-bit error, and a double-bit error. In addition, by sharing a current-controlled ring oscillator circuit that uses a current-starved inverter in the VPP, VNN, and VNNL charge pumping circuits that share a single ring oscillator in the erase and program operation modes of the MTP IP and using the regulated VPVR as power, the pumping capacitor size is reduced, and a new technology to reduce ripple voltage variation is proposed. Meanwhile, in the VNN level detector circuit that detects whether the VNN has reached the target voltage, a folded-cascode CMOS OP-AMP whose output swing voltage is almost VDD is used instead of a differential amplifier circuit with a PMOS differential input pair to ensure that normal VNN level detection operation occurs.

Triboelectric Nanogenerators for Self-Powered Degradation of Chemical Pollutants.

Environmental and human health is severely threatened by wastewater and air pollution, which contain a broad spectrum of organic and inorganic pollutants. Organic contaminants include dyes, volatile organic compounds (VOCs), medical waste, antibiotics, pesticides, and chemical warfare agents. Inorganic gases such as CO2, SO2, and NO x are commonly found in polluted water and air. Traditional methods for pollutant removal, such as oxidation, physicochemical techniques, biotreatment, and enzymatic decomposition, often prove to be inefficient, costly, or energy-intensive. Contemporary solutions like nanofiber-based filters, activated carbon, and plant biomass also face challenges such as generating secondary contaminants and being time-consuming. In this context, triboelectric nanogenerators (TENGs) are emerging as promising alternatives. These devices harvest ambient mechanical energy and convert it to electrical energy, enabling the self-powered degradation of chemical pollutants. This Review summarizes recent progress and challenges in using TENGs as self-powered electrochemical systems (SPECs) for pollutant degradation via photocatalysis or electrocatalysis. The working principles of TENGs are discussed, focusing on their structural flexibility, operational modes, and ability to capture energy from low-frequency mechanical stimuli. The Review concludes with perspectives and suggestions for future research in this field, hoping to inspire further interest and innovation in developing TENG-based SPECs, which represent sustainable and eco-friendly solutions for pollutant treatment.

Barriers to quality cancer care: a qualitative exploration of oncology case managers’ experiences in facilitating guideline implementation in Taiwan

BackgroundIn cancer care, the use of clinical practice guidelines (CPGs) has been shown to improve the quality and effectiveness of medical services. To facilitate physicians’ adherence to these guidelines, Taiwan established the position of oncology case manager (OCM) in 2010, one of whose responsibilities is to monitor physicians’ compliance. However, there have been few explorations of their experiences and the barriers they face in facilitating guideline implementation.ObjectiveThe aim of this study was to explore how OCMs carry out their roles in facilitating the implementation of CPGs in Taiwan and the challenges they encounter in this process.MethodsIn this study, a qualitative interpretative phenomenological analysis (IPA) approach focusing on interpreting phenomena was adopted. The subjects were eight OCMs from the same hospital in Taiwan. Data collection primarily involved conducting interviews, supplemented by document analysis.ResultsThe analysis revealed the following challenges for OCMs in the process of facilitating guideline implementation: (1) Local production: Self-directed exploration leads to significant pressure. (2) Operational modes: Difficulties arise in the “low-ranking overseeing high-ranking” approach. (3) Accountability mechanisms: OCMs are saddled with the chore of managing evaluation.Conclusion/practical implicationsGuidelines are vital tools to ensure the quality of cancer care. However, based on the experiences of OCMs, shortcomings in institutional design, hierarchical organizational culture, misconceptions about the role of OCMs, and a lack of support from management have been identified as key obstacles in the implementation process. Suggestions of ways to address these challenges and promote successful guideline implementation are proposed.

Optimized leakage control in CMOS NAND gates: the in-triggering technique

Abstract Leakage power, now the largest contributor to integrated circuit power consumption, is rising quickly, according to the International Technology Roadmap for Semiconductors (ITRS). As CMOS (complementary metal-oxide semiconductor) technology continues to shrink to deep submicron levels, gate leakage and subthreshold have become important components that contribute to total power dissipation. To address this problem, many methods have been put forth, especially at the circuit level. In 45 nm CMOS, variability and short-channel effects limit noise margins and compromise gate delays, thereby compromising the timing closure and robustness of ultra-low voltage circuits. The resulting supply voltage guardband may reduce energy efficiency in order to achieve a reasonable production yield. Furthermore, the high leakage currents of these technologies decrease energy efficiency when idle intervals are prolonged. In this study, two designs of a novel two-input NAND gate at 45 nm CMOS technology are constructed using eight transistors (8-T). A novel circuit technique named "In-Triggering (INDEP with Bi-Triggering)" is presented in this study with the goal of lowering subthreshold leakage in digital circuits. This method is thoroughly contrasted with other leakage reduction strategies now in use, such as Base, Sleepy LECTOR, LECTOR, INDEP, and Bi-Triggering procedures. Evaluation is done using key performance measures such power-delay product (PDP), latency, subthreshold leakage power, and total power consumption. 45-nm Predictive Technology Models (PTM) with a nominal supply voltage of 1V are used in the investigation. According to our findings, the suggested In-Triggering technique outperforms the conventional NAND gate in terms of speed by 12% and significantly reduces leakage power by up to 56%. Furthermore, compared to the Base, Trig01, and INDEP NAND gates, the method offers mean power savings of 58.8%, 36.1%, and 30.7%, respectively. At supply voltages of 1V, a comprehensive comparison and verification are then conducted utilizing the several proposed and existing methodologies. The effectiveness of the In-Triggering technique in reducing leakage power in CMOS circuits is confirmed by comparing these results to the most well-known design strategies for both active operation and sleep modes.

METHODOLOGY FOR OPTIMIZING THE FUNCTIONING OF THE OPTOELECTRONIC SURVEILLANCE SYSTEM

Context. Radar, thermal imaging, and video surveillance means are actively used in the protection of the state border. Together with the appropriate communication equipment, they allow to create optoelectronic surveillance systems, which are the basis for the intellectualization of border protection. The effectiveness of such systems is significantly affected by the peculiarities of their functional and structural design. A rational structural design, even in difficult physical and geographical conditions, allows for a high level of surveillance efficiency. However, the functional component also has a significant impact on improving the system efficiency. In many cases, the functioning of the elements of the optoelectronic surveillance system occurs under conditions of power supply restrictions. Such limitations determine the need for a rational choice of modes of use of certain types of surveillance equipment at certain time intervals in order to ensure effective surveillance, taking into account the time of day and weather conditions. The imperfection of the scientific and methodological apparatus for optimizing the functioning of optoelectronic surveillance systems determines the relevance of this study. Objective. The aim of the work is to develop a methodology for optimizing the optoelectronic surveillance system functioning by rationally selecting the modes of operation of different types of surveillance equipment in certain time intervals, taking into account the time of day and weather conditions in which they are used. Methods. The paper sets and investigates the two-criteria problem of choosing the modes of operation of different types of observation equipment of an optoelectronic surveillance system at separate time intervals, taking into account the time of day and weather conditions in which they are used, which ensures maximizing the efficiency of the optoelectronic surveillance system while minimizing the power consumed by active types of surveillance equipment in the presence of boundary restrictions on the efficiency and power consumed by the system. The proposed indicator for assessing the effectiveness of the system allows us to assess the level of impossibility of uncontrolled crossing of the perimeter of the protected area by an intruder. The peculiarity of this methodology is the possibility of ensuring a significant reduction in the level of energy consumption by the system components due to a slight decrease in the efficiency of monitoring. Results. The paper proposes an alternative approach to assessing the effectiveness of the optoelectronic surveillance system, the idea of which is that instead of assessing the effectiveness of surveillance over the entire sector of the controlled area of the border, the effectiveness of control is assessed only along the perimeter of this area. This approach significantly reduces the computational complexity of the problem of finding the value of efficiency which further simplifies the solution of problems of structural optimization of surveillance systems. A software and algorithmic implementation of the methodology for optimizing the functioning of an optoelectronic surveillance system is proposed. Using the developed software, a rational choice of modes of operation of certain types of surveillance equipment at certain time intervals was carried out taking into account the time of day and weather conditions. Conclusions. The use of the proposed methodology makes it possible to optimize the modes of operation of the optoelectronic surveillance system, taking into account the limiting factors in terms of efficiency and power consumption when using the same types of surveillance equipment on all towers of the system. A possible direction for improving the methodology is its adaptation to cases where different types of surveillance equipment are used on different towers of the system.

Research on the Integrated Converter and Its Control for Fuel Cell Hybrid Electric Vehicles with Three Power Sources

Separate DC-DC converters for each energy source are typically configured in fuel-cell hybrid vehicles. This results in a complex control structure of the powertrain system, low energy density of the converter, and high cost due to the large number of components. Conducting research on DC-DC converters with good energy flow management and high integration is a trend to solve such problems. Based on the analysis of the basic functional structure of the converter, this paper designs a buffering unit circuit with energy collection and distribution functions and appropriately connects it with the pulse unit circuit of the converter. Through device optimization reuse and power transmission path integration, a class of non-isolated four-port DC-DC converters is constructed, which consists of an auxiliary energy charging module, input energy source control module, braking energy feedback module and forward bootstrap boost circuit. This converter has two bi-directional ports, a uni-directional input and a bi-directional output, for separate connection to the power batteries, supercapacitors, fuel cells and DC bus. It can adapt to the fluctuation of the vehicle’s driving condition while achieving dynamic and flexible regulation of power flow and can flexibly allocate power according to the load current and voltage level of energy. It can realize a total of 14 operation modes, including six output power supply operation modes, five auxiliary power charging operation modes, and three braking energy regeneration operation modes. Furthermore, the mathematical model of this converter is constructed using the state-average method and the small-signal modeling method in order to achieve the responsiveness and stability of switching multiple operating modalities. The PI control parameters are optimized using the particle swarm optimization algorithm to achieve optimized control of the converter. The simulation system is set up using MATLAB R2024a to verify that the proposed converter topology and algorithm can dynamically allocate appropriate current paths to manipulate the power flow under various operating conditions, effectively improving the utilization rate and efficiency of energy. The converter has the characteristics of high gain and high power density, which is suitable for three-energy fuel cell hybrid electric vehicles.

Design and Experimental Validation of a Battery/Supercapacitor Hybrid Energy Storage System Based on an Adaptive LQG Controller

Hybrid energy storage systems (HESSs) are essential for adopting sustainable energy sources. HESSs combine complementary storage technologies, such as batteries and supercapacitors, to optimize efficiency, grid stability, and demand management. This work proposes a semi-active HESS formed by a battery connected to the DC bus and a supercapacitor managed by a Sepic/Zeta converter, which has the aim of avoiding high-frequency variations in the battery current on any operation condition. The converter control structure is formed by an LQG controller, an optimal state observer, and an adaptive strategy to ensure the correct controller operation in any condition: step-up, step-down, and unitary gain. This adaptive LQG controller consists of two control loops, an internal current loop and an external voltage loop, which use only two sensors. Compared with classical PI and LQG controllers, the adaptive LQG solution exhibits a better performance in all operation modes, up to 68% better than the LQG controller and up to 84% better than the PI controller. Therefore, the control strategy proposed for this HESS provides a fast-tracking of DC-bus current, driving the high-frequency component to the supercapacitor and the low-frequency component to the battery. Thus, fast changes in the battery power are avoided, reducing the degradation. Finally, the system adaptability to changes up to 67% in the operation range are experimentally tested, and the implementation of the control system using commercial hardware is verified.

Modeling of Power Line Operation Modes Based on Long Line Equations in Hyperbolic Functions Taking into Account Specific Corona Losses with Nonlinear Conductivity

Modeling of Power Line Operation Modes Based on Long Line Equations in Hyperbolic Functions Taking into Account Specific Corona Losses with Nonlinear Conductivity

METHODS OF RESEARCH OF RESONANT CONVERTERS

Analytical study of DC-DC resonant converters for the purpose of their analysis and correct design is a topical task. Currently, the fundamental harmonic method and the time domain analysis method are used to solve this problem. The use of the fundamental harmonic method for analyzing the steady-state characteristics of an LCC converter is simple only when using an LC smoothing filter at its output. For the widely used LCC converter with a capacitive filter at the output, the fundamental harmonic method yields a significant error. Therefore, the characteristics of an LCC converter are currently studied mainly by time analysis and simulation methods. The purpose of the study is to substantiate external characteristics of the LCC type converter using fundamental harmonic and time domain analysis methods and to compare the obtained results with the results of simulation modeling. Materials and methods. Mathematical modeling of the converter was carried out using methods of circuit theory and automatic control. Studying the converter with the help of time domain analysis, vector-matrix methods for solving differential equations, methods of separating motion and fitting were used. Simulation modeling of the converter was carried out in the MATLAB/Simulink dynamic modeling environment. Research results. External (load) characteristics of converters along with dependences of voltage gain on switching frequency allow to justify the choice of converter type and recommendations for their design. The derivation of external characteristics of the converter and dependences of short-circuit current and no-load voltage on switching frequency is given by the fundamental harmonic method. The time domain analysis is carried out for the most complex three-interval on a half-cycle switching mode of converter. The vector-matrix method is used to solve differential equations describing processes on three intervals of converter linearity. Analytical relationships are obtained that allow to calculate transient processes by the fitting method and to determine the characteristics of the steady-state mode. The latter is significantly complicated with an increase in the number of converter linearity intervals on a half-cycle of switching. This is explained by the fact that before calculating the characteristics of the steady-state mode, it is necessary to solve the nonlinear equation of this mode, which is greatly complicated already at three intervals of linearity on a half-cycle. Conclusions. The fundamental harmonic method for the LCC converter has limited application, since it gives approximate results, which are refined by more accurate methods. The time domain analysis method is the most suitable and accurate method of study. But its application becomes more complicated with the increase in the number of converter linearity intervals when analyzing its steady-state operating mode.

Analyzing the Influence of Coolant Pressure Fluctuation Natural Frequencies on the Vibration Strength of the Main Coolant Pipeline and Steam Generator Header Metal at NPPs with VVER Reactors in the Nominal Operation Mode

Analyzing the Influence of Coolant Pressure Fluctuation Natural Frequencies on the Vibration Strength of the Main Coolant Pipeline and Steam Generator Header Metal at NPPs with VVER Reactors in the Nominal Operation Mode