Normal Operation Mode Research Articles

Анализ закритической устойчивости распределенных информационных систем реального времени

The article describes an approach to the numerical analysis of the stability of distributed information systems under a load that varies over time allowing for a short-term load exceeding critical values. Information systems are considered as imperfect queuing systems in which the intensity of the message flow may depend on the size of the queues of applications. Based on this approach, criteria for the stable and unstable behavior of the system under load are formulated, where the stable behavior of the system is understood as the ability of the system to return to its normal mode of operation independently when the external load drops below the critical value, and unstable one when there is the transition to an emergency state. As examples, the most common types of unstable systems are considered, as well as an example of a distributed system that implements a complex queuing system, which, depending on the characteristics of the service, can be either stable or unstable. The analysis of such a system is carried out, which is confirmed by the results of numerical simulation. Based on the analysis results, zones of stability and instability are determined. Features of the implementation of distributed real-time information systems are considered, practical recommendations for the implementation of sustainable information systems are given

Проблемы разработки и внедрения средств индивидуальной защиты персонала радиационно- и химически опасных объектов, аварийно-спасательных формирований и населения

The article presents a brief review of the activities of the laboratory "Personal protection equipment for the personnel of hazardous production facilities" for creation of the regulatory-legal and regulatory-methodological support system for personal protection of the personnel of radiation and chemical hazardous facilities, of regular and non-staff emergency rescue teams of Rosatom State Corporation and of FMBA of Russia as well as of the population living in the influence area of the mentioned facilities. The issues of standardization and certification of personal protective equipment at NPPs and in the field of atomic energy use — both in the normal operation mode of dangerous objects, and in emergency situations of peace and war time are considered. The problems arising in the implementation of innovative personal protective equipment, primarily due to international obligations, are shown.

RECIRCULATION PUMP SCALAR CONTROL SYSTEM ELECTRICAL DRIVE MODEL S DEVELOPMENT AND RESEARCH

On the basis of the analysis of the used models of the electric motor at synthesis of the asynchronous electric drive with frequency control mathematical and simulation models are received. The structural scheme of the three-circuit scalar control system of the electric drive of the recirculation pump in the form of the simulation model for which the parameters of the scalar control system were calculated is offered and realized. The calculation of parameters and coefficients of the mathematical model of the solar control system of the electric drive is given. The calculations of the pressure of the recirculation pump are presented. The scheme of the simulation model of the subsystem of the unit for calculating the performance and pressure of the recirculation pump is given. Calculations and simulation model of PI current regulator are presented. Calculations and simulation model of PID-speed controller subsystem are given. Calculations andsimulation model of PI-pressure regulator subsystem are presented. Calculations of scalar control system parameters in the form of MathCad scripts are presented. On the received model processes of work of the electric drive of the pump in normal and emergency operating modes were considered. Calculations and simulation model of voltage and frequency converter subsystem are given. Calculations of parameters and coefficients of the scalar control system are given. The simulation model of the sensor unit subsystem is given. The calculations of the frequency converter and the voltage converter are given. The transfer functions of the voltage and frequency converter of the scalar control system of the asynchronous electric drive of the recirculation pump are presented. The simulation model of the fan load subsystem of the scalar control system of the boiler's recirculation pump is presented. The table presents an analysis of the transient characteristics of a two-phase mathematical model of an induction motor. The analysis of transient characteristics of the scalar control system of the recirculation pump is presented.

ANALYSIS OF EMERGENCY OPERATION OF WATER PIPELINES

In this work, the influence of individual sections of the water supply network on the dynamics of nodal heads in emergency operating modes is investigated. During accidents in the network sections, the dynamics of the head changes, the supply of water to the network decreases, areas with insufficient heads are formed. The subject of the analyzed stage of research is the influence of individual sections of the network on the location and size of areas with insufficient head. To determine the influence of individual sections of the network on head dynamics, methods of mathematical modeling of flow distribution in the water supply network, methods of hydraulic calculations of water supply networks were used. The results of studies of formation and change of areas with insufficient head taking into account emergency situations for networks with different structure and configuration are presented. The tasks to be performed by the flow management system at the network design stage are defined. Based on the results of the studies, the water supply conditions were evaluated during the formation of areas of insufficient pressure. Proposed algorithm consists of visualization of network structure, simulation of emergency situations, hydraulic calculations of network in normal and emergency operation modes, determination of actual head in network nodes, clarification of location of control nodes, calculation of required head of pumps in emergency operation mode. The proposed method allows you to determine the priority selection of network sections during its reconstruction and restoration. Modeling and analysis of pressure zones in the network allows you to change the number and location of pressure control units depending on the need. The proposed recommendations on flow management can be implemented in the work of utility dispatch services.

Dynamic frequency scheduling for CubeSat's on-board and data handling subsystem

<p>CubeSat is a small-sized satellite that provides a cheaper option for the manufacturer to have a fully operational satellite. Due to its size, CubeSat can only generate limited power, and this will restrict its functionality. This research aims to improve CubeSat’s power consumption by implementing the dynamic voltage and frequency scaling (DVFS) technique to on-board and data handling subsystem (OBDH). DVFS will find the best operating frequency to execute all of OBDH’s task. This paper explains how we determined the task set, representing all routine tasks performed by OBDH during normal operation mode. We have simulated the task set using two DVFS algorithms, static earliest deadline first (EDF) and cycle conserving edf (CC EDF). The result shows that both scheduling algorithms give a similar result to our task set. However, when the scheduler is configured as non-preemptive, the simulator failed to schedule the critical task. It means that the system fails to work as intended. Therefore, we conclude that we need to implement mixed-criticality scheduling to prevent critical tasks from being aborted by the system.</p>

Structural analysis of large-scale SS collecting mirrors for ITER diagnostics

ITER is a nuclear fusion research and engineering project. It is supposed to be the first fusion device designed for testing the integrated technologies, materials, and physical aspects necessary for development of the commercially available fusion-power plant. One of the important components of the project is optical diagnostic systems with collecting mirrors. These mirrors have to provide stability of optical systems under severe loads of different types that could possibly arise in the tokamak. The collecting mirrors of several ITER diagnostics have a large scale and should be installed into diagnostic ports. Thermal stress analysis of the mirror updated design is aimed to obtain deformation and rotation values of the mirrors’ reflecting surfaces in order to conduct ray tracing analysis and to edit mirrors alignment to provide correct functioning of the optical systems. The maximum temperature values of the Divertor Thomson Scattering collecting mirrors were estimated for the normal operation mode. The FE model of the second mirror takes into account all the force boundary conditions, basic kinematic boundary conditions and constraints. Boundary conditions taken for the simulation were applied on surfaces contacting with the diagnostic rack. Thermally stressed state was calculated and corresponding displacement and rotation distributions were obtained.

Modeling of the stress-strain state of ITER upper ports №2 & №8 constructions’ components under thermal, electromagnetic and inertial loads

This paper presents the results of calculations of the upper port plug (UPP) of the ITER upper ports №2 and №8. Detailed finite-element models of the UPP structure were developed taking into account nonlinear contact interaction between the diagnostic shield module with extension frame and the UPP structure. In the structural analysis under design loads the stress-strain state (SSS) taking into account bolts pretension was obtained. Besides, the FE model includes cooling system pipes and boron carbide shielding. In the thermal analysis of the UPP for baking and normal operation modes the neutron analysis data was taken into account. The UPP cooling systems’ hydrodynamic characteristics were calculated including the flow-pressure characteristics. Subsequently, the whole UPP construction flow and pressure characteristics were evaluated taking into account the presence of throttling devices in the UPP hydraulic circuit. Structural analysis of the UPPS during seismic and electromagnetic events was carried out using the response spectrum method based on the response spectra at the UP point of the ITER building and interface electromagnetic loads due to the vacuum vessel movements respectively. The FE model includes port extension from the generic upper port plug model. Except this, the response spectra at the tenant attachment points were calculated using power spectral density analysis. Laplace force distribution in the UPP under different scenarios of plasma disruption was calculated. The electromagnetic model was significantly refined and includes the extension frame trays. Based on the electromagnetic analysis data, the structural analysis of the UPP under electromagnetic loads was carried out.

Operating modes of a magnetized direct-current discharge in helium at pressures ∼10 Pa

A high-pressure direct current magnetron discharge is analyzed using a self-consistent two-dimensional fluid model. This discharge has potential interest in plasma switching applications due to its ability to generate rather dense (plasma density of ∼1019 m−3) stable nonequilibrium plasmas at pressures of ∼13.3 Pa (100 mTorr). This discharge has several advantages over nanosecond pulsed high pressure discharges used in conventional plasma switchers since it operates at much lower voltages and lower gas pressures, with the advantage of much longer cathode lifetime. In the present paper, we analyze the operating modes of this magnetron discharge for conditions close to that of Sommerer et al. [J. Phys. D: Appl. Phys. 52, 435202 (2019)]. We observe the subnormal and normal modes of the magnetron operation whose physics differs from that typical for unmagnetized plasmas.

Single-Phase Transformerless Line Interactive Uninterruptable Power Supply with Two Independent Control Algorithms

This paper presents the development of two independent control algorithms for an Uninterruptable Power Supply (UPS). It is a mitigation tool to mitigate power interruption. The UPS circuit consists of a bidirectional buck-boost DC-DC converter, a rechargeable battery and a DC-AC/AC-DC converter. The bidirectional DC-DC converter has a function of charging (buck) or discharging (boost) the battery for maintaining DC-link voltage connected to the DC-AC/AC-DC converter. During the normal mode operation, the DC-AC/AC-DC converter supplies voltage to the bidirectional converter by performing AC to DC conversion. Instead, during the backup mode, the converter supplies voltage to the load by performing DC to AC conversion. In this work, a single-loop voltage control algorithm regulates the bidirectional converter. For the DC-AC/AC-DC converter, a multi-loop control algorithm regulates the output current using the inner loop and the output voltage using the outer loop. MATLAB/Simulink simulates the UPS to determine its performance during normal and backup mode operation. From the simulation results, both independent control algorithms can regulate the operation of both converters during both modes of operation. As a result, the UPS system is capable of supplying sinusoidal waveforms with low Total Harmonic Distortion (THD) of output current and output voltage. Both THD values are below 4%.

Adaptive Identification of Control Objects in Systems with Standard Controllers

The report is devoted to the study of the problem of parametric identification of controlled dynamic systems in their normal operation mode using a model with adjustable parameters. The task of determining parameters of test signals providing the specified accuracy of identification is considered. The peculiarity of the work consists in imparting adaptive properties to the identification procedure, which makes it possible to minimize the negative effect of “swinging” of the controlled object on its output when special test signals are applied.

Some Tips on Numerical Modeling of Airflow and Fires in Road Tunnels

The efficiency of tunnels systems is often evaluated using numerical simulations. This concerns both to normal and emergency mode of tunnel systems operation. Therefore the safety level of tunnel users may depend on the quality of numerical models being built. The most often studied areas cover the researches on natural and forced airflows in the normal mode and on fire development and smoke spreading in the emergency mode as well as modeling of fan operation. Thus, many software packages implementing Computational Fluid Dynamics (CFD) are applied here. Despite the available software is recognized as reliable, the problem arises because the built numerical models should be validated at least partially with experimental data. There is a shortage of experimental data from real tunnels due to high costs and many organizational or formal difficulties. Some researchers use data from scaled experiments, but this leads to problems connected with scaling. The paper presents the application of two widely used software packages—Fire Dynamics Simulator (FDS) and ANSYS Fluent to reproduce some scenarios of the operation of a tunnel ventilation system for normal and emergency mode. Most of results were compared with data obtained by own full scale measurements or data available in literature. Some practical issues concerning the application of FDS and ANSYS Fluent were discussed as well.

Strength estimation of the ITER Lower Vertical Neutron Camera at thermal loading

Lower Vertical Neutron Camera (LVNC) is a diagnostic system installed into the Diagnostic Rack of the ITER Lower Port #14. LVNC includes water cooling system, six detectors units, electrical feedthroughs and cables. Finite element model and finite volume model created with ANSYS software were used to obtain temperature and stress-strain state during Normal Operation and Baking modes.

Second‐order SMO‐based sensorless control of IM drive: experimental investigations of observer sensitivity and system reconfiguration in postfault operation mode

In normal operation mode, sensorless speed-controlled motor drives should be more reliable, less expensive and less bulky than their counterparts with a speed sensor. The sensorless drive structure allows avoiding the electromagnetic and vibratory sensitivity of the mechanical sensor, the additional connecting circuits, additional space for the sensor, its price and maintenance requirements. However, in postfault operation mode, the robustness of speed sensorless control strategies has been poorly addressed in the study. Accordingly, this study deals with an experimental study of the robustness and the availability of speed-controlled induction motor (IM) drives without speed sensor in the presence of inverter open-switches faults. For that purpose, a super twisting algorithm-based observer for motor speed estimation is proposed for experimental investigation. Experimental results are performed upon 3-kW IM drive by using dSPACE digital signal processing controller board. Experimental investigations evaluate the performances of the method used for the control without speed sensor in prefault, postfault and regeneration operation modes.

Wind/Thermal Power Combined Frequency Control Strategy Based on Virtual Weight Coefficient

The existing virtual inertia control increases the system's moment of inertia, which is beneficial to reduce the short-term frequency drop, but has no supporting effect on the steady-state frequency, and the fan is likely to cause negative power penetration of the system during the recovery of kinetic energy after discharge, resulting in a frequency twice. collapse. In order to realize the transient control performance of grid transient and steady-state frequency under high-permeability wind power, a robust integrated frequency response model with virtual inertia support and steady-state frequency secondary support is constructed. The model includes wind-fire with high wind penetration rate. The bundled DC delivery system and the 500 kV large-scale transmission grid with wind farms control the power contribution of the fan at different time scales with the system frequency change rate. The additional frequency secondary support control strategy establishes the wind speed and the virtual inertia of the fan. The relationship between the coefficient and the system frequency sensitivity function, the dynamic response system steady-state frequency requirement, the wind turbine is introduced into the wind farm virtual weight coefficient after the primary unit of the synchronous unit, and the stratified and step-by-step normal operation mode is provided to provide the transient/stable for the grid. Dual frequency support at full time scale. Based on PSCAD software, a robust integrated frequency control hardware-in-the-loop simulation platform is built to verify the correctness of the proposed method and analysis conclusions.

MATHEMATICAL MODELS OF RELIABILITY OF POWER SUPPLY SYSTEMS

Ensuring reliability is one of the most important issues in the creation and operation of any technical system. This is especially important for complex systems, such as power supply systems with internal and external connections consisting of many elements. The task of ensuring the reliability of power supply systems includes a whole set of technical, economic and organizational measures aimed at reducing damage caused by violations of the normal mode of operation of electricity consumers. To obtain information about the reliability of elements of power supply systems, it is necessary to study a fairly large number of identical elements over a long period of time. In the real conditions of an industrial enterprise, this creates certain difficulties, so it is possible to conduct an accelerated reliability test using mathematical modeling [3].
 The article discusses some ways to solve the main problem of reliability theory - building a mathematical model and obtaining criteria for selecting optimal options for power supply systems. In this paper, the main materials for calculating the reliability of power supply systems using the mathematical apparatus of probability theory are presented.

A Dual-Mode Modulation Technique for Controlling the Average Neutral Point Current in Neutral-Point-Clamped Converters

This article presents a dual-mode modulation technique that aims to control the average current flow into the neutral point (NP) of the NP-clamped (NPC) converter without the need for any additional hardware. The two modes of operation are normal mode and compensating mode. In the normal operation mode, all the three phases switch between two consecutive voltage levels (between the positive or negative dc-rail and the NP) in a switching period. In the COM, at least one of the phases switches between the positive and negative dc-rails in a switching period. An analytical solution is developed to determine the duration of these two operation modes within each fundamental cycle based on the converter's operating condition. An advantage of this solution is that it can be generalized for balancing the capacitor voltages in all applications employing NPC converters. The proposed solution also determines the maximum average NP current injection capacity of the NPC converter under dual-mode modulation technique, which indicates the stable operating range of the converter. The performance of the proposed modulation technique is validated experimentally for various loading conditions.

Resiliency-oriented optimal scheduling of microgrids in the presence of demand response programs using a hybrid stochastic-robust optimization approach

Natural incidents with a low occurrence probability and high impacts like windstorms and earthquakes, threaten the optimal operation of the distribution networks. Hence, some operational solutions are required to improve network resiliency. Microgrids (MGs) provide a proper solution for the resiliency enhancement of distribution networks to reach the optimal resilient operation under such incidents. Also, the inherent uncertainties make the resilience-oriented optimal operation of MGs more critical and should be modelled by efficient uncertainty modelling tools. In this paper, a hybrid stochastic-robust optimization (HSRO) approach is used to get the optimal scheduling of an MG under normal and resilient operation mode. The impact of the upstream grid price uncertainty on the optimal scheduling of MGs is modelled using the robust optimization approach. Other dominant uncertainties, including the wind power, photovoltaic (PV) power, and active/reactive electrical loads, are also modelled by stochastic optimization via generating a set of relevant scenarios. In addition, adjustable and interruptible demand response programs (DRP) are implemented to improve the resilient operation of MG under incidents. The proposed approach tries to improve the MG operation under uncertainties during the resilience and normal mode of network. Furthermore, this paper concentrates on the robust and normal strategies adopted for the resilience-oriented scheduling of MGs. The effectiveness of the proposed framework is evaluated through a large-scale MG test system.

Energy loss and emissions of engine compression rings with cylinder deactivation

A novel integrated multi-physics assessment of the piston top compression ring of an internal combustion engine under normal operation mode, as well as subjected to cylinder deactivation is carried out. The methodology comprises ring-liner thermo-mixed hydrodynamics, elastodynamics of ring, as well as combustion gas blow-by and emissions. Therefore, the analysis provides prediction of ring-liner contact’s energy losses and gas power leakage across the piston and ring crevices, as well as the resulting emissions. Cylinder deactivation (CDA) technology reduces the unburnt fuel entering the ring-pack crevices, as well as the emissions. It is also shown that the frictional and gas leakage power losses are exacerbated under CDA by as much as 20%. Although this is much lower than the potential gains in fuel usage when using CDA. The optimisation of the piston compression ring would provide further fuel efficiency and improved emissions, an issue which has not hitherto received the attention which it deserves. The in-depth analysis has also shown that CDA reduces the predicted CO, NOx and HC emissions by nearly as much as 8.5%, 10% and 8.7%, respectively.

Определение периода повторяемости электромагнитных процессов в аварийных режимах работы многофазных вентильных двигателей малой мощности

Increasing requirements for the reliability indicators of technical systems lead to the need to apply new approaches to the design of electric machines and electric drives as an electrical complex, one of which is a systematic approach. To provide a set of increased reliability indicators, it is proposed to use multiphase AC converter-fed motors that differ in structural and algorithmic redundancy It is shown in order to implement variants of AC converter-fed motor circuit, in addition to reliability indicators, a quantitative assessment of its energy capabilities in normal and emergency operating modes is necessary. The most important stage of the practical implementation of the numerical process in the quantitative assessment of energy capabilities is to determine the period of repeatability of electromagnetic processes. The main issues of determining the period of repeatability of quasi-steady-state electromagnetic processes of an electromechanical energy converter of low-power multiphase AC converter-fed motors in the design of systems of increased reliability are considered. This made it possible to implement the numerical solution of systems of differential equations describing the physical processes in AC converter-fed motors with a variable structure of the electromechanical converter in normal and emergency operating modes.

Dynamic Ron Effect in GaN HEMT in a Zero-Voltage-Switching Circuit Due to Off-Resonance Operation

Dynamic ON resistance of GaN devices is a must-care point for users. In this paper, the reverse conduction of commercial GaN power transistors is studied. Even though the commercial HEMTs show stable performance in normal operation modes (off-to-on), significant dynamic ON resistance can be seen in some particular conditions. A test method is set up to evaluate dynamic R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> in a reverse-to-on mode. The conditions to activate the behavior are discussed, and the cause of dynamic R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> is possibly due to traps located in the gate region. Meanwhile, a wireless power transfer system operating at 6.78MHz is used to study the effect of reverse conduction mode on dynamic resistance at the circuit level. According to the change of the operation frequency, we find that the influence of reverse conduction on the dynamic R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> effect is not only affected by the value of reverse conduction voltage but also related to the operating mode of the device.