Normal Operation Mode Research Articles

Разработка и верификация имитационной модели процесса теплопередачи через оконный блок с теплоотражающими экранами

Window units account for the largest specific heat losses. The use of movable heat-reflecting screens and photovoltaic solar panels is of particular interest among the existing technologies to improve the thermal protection of windows. Despite the large number of scientific papers on this issue, which consider experimental laboratory studies and numerical simulation of heat transfer processes through window units, there is no data on the influence of the edge zones of a double-glazed window, as well as the areas of interface of the window profile and the light opening on the thermal processes that occur in these energy-saving units with screens. Vertical replacing of specific heat fluxes and temperature on the inner surface of the window unit strongly influences the correctness of determining the value of the minimum allowable temperature of the indoor air. Thus, the development and verification of models of the heat transfer process through a window unit with screens is an urgent task in the context of an indoor microclimate creation. Simulation numerical modeling is performed using the finite element method based on the fundamental laws of heat transfer. The authors have used the results of experimental studies of windows with heat-reflecting screens carried out in a certified climatic chamber. The authors have developed a two-dimensional simulation model of heat transfer through a window unit with heat-reflecting screens located in the partition wall of the climate chamber. The distribution of temperatures, air flow velocities, and reduced total thermal resistance along the height of a translucent structures has been studied. The adequacy of the proposed simulation model is confirmed by comparison with the results of the experiment in a certified laboratory, as well as data obtained by other authors and regulatory documentation. The use of heat-reflecting screens in the window unit increases the resistance to heat transfer by 1,6–3,7 times depending on their number. A significant decrease in temperature in the edge zones of the double-glazed window is revealed. The use of the developed simulation model makes it possible to determine the application of heat-reflecting screens in windows for intermittent heating systems including the case of using pre-drying air technology for humid, wet, or normal operation modes of industrial premises.

Study of the influence of the parameters of modern grounding wires on the value of power losses in them for overhead power lines of 330-750 kV

Introduction. The problem of estimating power losses in grounding wires with built-in fiber optic cable for overhead power lines of voltage class 330-750 kV is relevant, while it is obvious that the amount of losses depends on the chosen brand of wire. Problem. In the article, an analysis of the influence of the parameters of grounding wires on the amount of losses that occur in them in the normal mode of operation of the overhead power lines is carried out. Goal. The purpose of the work is to determine the criterion for the selection of grounding wires with a built-in optical fiber cable under the condition of increasing the energy efficiency of electricity transmission. Methodology. To calculate power losses in grounding wires, the methods of electromagnetic field theory were used, while taking into account the location of phase conductors on various types of towers of operating 330-750 kV overhead power lines and the possible current load of such lines. Results. The paper analyzed the dependence of losses in the grounding wires of the overhead power lines on the ratio of its active and reactive resistances, determined in which range of this ratio the losses will be close to the maximum. It is shown that the amount of specific power losses in the grounding wires of 330-750 kV overhead power lines in its normal operating modes can range from 1.6 kW/km for the 750 kV lines to hundreds of W/km for the 330 kV power lines. Originality. For the first time, it is recommended to use grounding wires with built-in fiber optic cable with running active resistance in the range of no more than 0.25 Ohm/km, which will minimize power losses and increase the energy efficiency of the 330-750 kV overhead power lines. Practical value. The obtained results can be applied at the stage of designing new or modernizing existing overhead power lines in order to reduce losses and increase the energy efficiency of lines.

A high-efficiency burst mode boost converter with a sharing main power NMOS for start-up

This paper presents a high-efficiency boost converter with a wide input range and a start-up strategy of sharing main power NMOS which can start-up at an input voltage of 700 mV. A burst mode with boundary conduction mode (BMBCM) control is utilized in the proposed boost converter to achieve high efficiency across the wide input power range. A method is also suggested to determine the optimal peak inductor current for a given input range. Compared to other start-up strategies, the proposed start-up circuit reduces chip area by sharing the main power NMOS with the normal operation mode, eliminating the need for an additional start-up power transistor. A new ultra-low-power voltage detection circuit is used to control the start-up process. The proposed boost converter is designed and fabricated in a 180 nm BCD process with an active chip area of only 0.33 mm2. The circuit achieves a peak efficiency of 94.8% at an input voltage of 3 V and an output voltage of 3.6 V, while maintaining an efficiency of at least 65.9% across the input power range of 7 μW to 300 mW.

Joint Optimal Energy Management and Voyage Scheduling for Economic and Resilient Operation of All-Electric Ships Considering Safe Return

Marine power systems are isolated from external grids, making them more vulnerable than land-based power systems. When ships are sailing on the ocean, complicated maritime environment and electrical component failure pose a crucial challenge to a safe and resilient shipboard power system. Different from fixed terrestrial microgrids, all-electric ships (AES) are mobile transportation vessels, complying with the navigation regulation of safe return to port. Thus, the economic and resilient operation needs to be considered from both energy and transportation aspects. In this regard, this study proposes a two-stage coordinated optimization framework for an AES, taking into account the impact of navigation. In the first stage, the normal operation mode follows the pre-voyage plan, which jointly optimizes voyage and energy management to reduce the whole voyage operation costs and greenhouse gas emissions simultaneously. In the second stage, a resilience-oriented optimization is developed to defend against emergencies by rescheduling navigation speed and generation. Furthermore, resistance during the whole AES navigation is also considered. Numerical results demonstrate the necessity of resistance impact on the voyage and the efficiency of the proposed operation scheme in economic and resilient operation for AESs.

Process-Voltage-Temperature Variations Assessment in Energy-Aware Resistive RAM-Based FPGAs

Resistive Random Access Memory (RRAM) technology holds promises to improve the Field Programmable Gate Array (FPGA) performance, reduce the area footprint, and dramatically lower run-time energy requirements compared to the state-of-the-art CMOS-based products. However, the integration of RRAM in FPGAs is hindered by the high programming power consumption and by non-ideal behaviors of the device due to its stochastic nature that may overshadow the benefits in normal operation mode. To cope with these challenges, optimized programming strategies have to be investigated. In this work, we explore the impact that different procedures to set the device have on the run-time performance. Process, voltage, and temperature (PVT) variations as well as time-dependent drift effect of the RRAM device are considered in the assessment of 4T1R MUX designs characteristics. The comparison with tradition CMOS implementations reveals how the choice of the target resistive state and the programming algorithm are key design aspects to reduce the run-time delay and energy metrics, while at the same time improving the robustness against the different sources of variations.

Power consumption regulation of enterprises for reducing of the energy system peak loads

Purpose. To propose measures for a partial solution to the problem of evening peak loads ensuring in the energy system of Ukraine by regulating the power consumption modes of industrial enterprises. This approach will reduce the level of such loads and align the power consumption profile. The methods. The methods of operations research and analysis of technological processes are used. The operation modes of the Ukrainian operating coal mines were studied and their electrical loading diagrams, which are formed by the appropriate technological processes, were analyzed. Findings. A comparative analysis of electrical loading diagrams of the power system and power consumption profiles of industrial facilities and the residential services was performed. The analysis showed the similarity of the electrical loading diagrams of coal mines, which is due to the typical mode of their operation, namely the presence of three work shifts (for coal mining) and one repair shift (for equipment maintenance). This creates prerequisites for the use of such enterprises as consumers-regulators of active power. As a result of which ways of "mitigation" of the problem of peak loads ensuring of the power system were proposed. Originality. The patterns of formation of the electric loading daily profiles for coal mines, determined by the operating mode of enterprises, were established.A new approach is proposed, which consists in changing the daily operation mode of coal mines, namely, moving the repair shift to a time that coincides with the period of evening peak loads in the Ukrainianpower system. Practical implementation. The practical value of this work lies in reducing the level of power consumption during peak loads in the power system,what is currently a very urgent problem for Ukrainian energy complex. The proposed approach allows to use the normal operation mode of a coal mine with the preservation of all necessary technological processes as an effective consumer-regulator of active load.

Effect of Initial Stress and Impedance Boundary in Transversely Isotropic Materials

This paper aimed at studying the effect of initial stress and impedance boundary surface on the elastic waves propagation in transversely isotropic materials. The governing equations of transversely isotropic materials with initial stress are treated in the [Formula: see text]-plane to obtain the phase velocities of two waves, quasi-longitudinal ([Formula: see text]) and quasi-transverse ([Formula: see text]) waves. The normal mode operation is employed to obtain the expression of the displacement components and stress components. The problem of reflection of incident waves at the impedance boundary of transversely isotropic material is also investigated in the presence of initial stress to obtain the amplitude ratios of reflected waves. The variations of displacement and force stress are illustrated with respect to the axis of propagation by employing amplitude ratio expression. The effect of initial stress and impedance parameters on the expression of displacement and force stress as well as amplitude ratios of transversely isotropic materials are illustrated graphically for a particular model.

Reduction of emissions and improvement of dynamic responses of a supercritical clean coal generation unit via neural network inverse control strategy

Coal power plants have been a major source of undesirable emissions. Despite the technological advancements in renewable energies, coal units are still in-service in many developed and developing countries due to their reliability, adequacy, and flexibility for power delivery. There are some promising technologies for cleaner operation during power production from coal, including supercritical boiler (SC) design and carbon capture and storage (CCS), however, the challenging in innovating effective methods is still open to expand the boundary of knowledge in this speciality. This paper introduces a novel and simple method for reducing CO2 emissions and improving the dynamic responses of a 600 MW SC coal power plant by Artificial Neural Network (ANN) technique. A wide-range data-driven feedforward ANN model has been identified and verified for the various operations recorded as closed-loop data-sets, which covers all situations of startup, once-through mode, and even emergency shutdown of the unit. The closed-loop SC plant model has been augmented with an inverse multivariable coordinate NN controller, developed by analogous learning algorithm to improve the plant automation. With precisely selected setpoints, as operational rules, of temperature, pressure, and earliest possible power demand signals, the automated SC plant has been capable to operate with lower coal consumption - and thus lower emissions – than the existing operation strategy during startup, normal operation, and emergency shutdown modes. The improvement in dynamic responses have been quantified through simulations with comparison with existing performance, which have resulted in an overall average reduction of 2.143 Kg/s in coal consumption.

Enhancing the economic performance and resilience in a multi-area multi-microgrid system by a decentralized operation model

This paper proposes a multi-area multi-microgrid system (MAMMS) and uses a decentralized operation model to enhance the economic performance of microgrids (MGs) in normal operation mode and their resilience against extreme weather events. The proposed MAMMS includes distantly spaced multi-microgrid systems (MMSs), each has its own local network (LN) and several MGs with independent owners. In this system, MGs participate in the day-ahead intra-regional market to exchange power with neighboring local MGs (NLMGs) and LN. Also, to reduce the prediction error of loads, RESs' outputs, and events' impacts, MGs use a model predictive control-based approach and exchange power with NLMGs for each next hour by participating in the real-time intra-regional market (RTIRM). In the event of an incident, the distribution network operator interconnects the islanded MMSs together and grid-connected MMSs via available tie lines. So, if MGs of MMSs affected by the incident cannot supply their total required power by RTIRM, they can participate in the inter-regional emergency market and buy power from other MMSs' MGs. This market is formed for each next hour and continues until the end of the incident. Numerical results show the effectiveness of this model for enhancing the economic performance and resilience of MGs.

Exposure of students (pupils) and employees of educational institutions in the Leningrad region to natural sources of radiation. Part 1: Results of a comprehensive survey

Currently, there is no methodological support for radiation monitoring and sanitary and epidemiological assessment of radon concentration (or radon EEC) and other parameters of the radiation situation in existing operated buildings. The paper presents a review of the protocols for conducting measurements of indoor Leningrad region with previously found elevated levels of radon concentration using long-term measurements. The survey revealed that highest values of indoor radon ECC were obtained using instant measurements in several educational institutions both in the normal operation mode of the buildings (up to 1106 Bq/m3) and after leaving the premises for 12 hours with closed windows and doors (up to 1586 Bq/m3) according to the requirements of paragraph 6.5 of MU 2.6.1.2838-11. High values of radon concentration were also obtained using long-term and short-term measurements (up to 4900 and 1420 Bq/m3, respectively). In addition, high values of radon flux density were detected (up to 2030 mBq/(m2·s)). The established hygienic norms for ambient dose equivalent rate indoors and outdoors were not exceeded in the surveyed educational institutions. The levels of gross alphaand beta activities in tap water sampled from the surveyed educational institutions were below the control levels, and an exceedance of intervention level for activity concentration of radon in analyzed samples was not detected. The results of the survey will be used for hygienic assessment of doses and health risks for students (pupils) and employees of several educational institutions of the Leningrad region due to exposure to radon and its progeny and can be used to improve the method for indoor radon concentration monitoring in existing operated public buildings in the Russian Federation, which in turn will make it possible to obtain correct values of public doses and health risks.

Method of determination of the railway rolling stock coordinates within the track circuit

This work aims to solve one of the essential problems in railway transport – control over the position of moving units within the race. A method of constant monitoring of the track circuit with a determination of the coordinate of the train shunt placement in the shunt mode of working is proposed to solve this problem. Since the model includes the primary parameters of the track circuit, which may change their values over time, it is suggested to determine them in another (normal) working mode of the track circuit. Therefore, according to the proposed model, the secondary and primary parameters of the track circuit are first determined in the track circuit's normal work mode. Next, already in the shunt mode of its work, the obtained parameters are used to determine the coordinates of the moving unit. According to this method, firstly, the work mode of the track circuit is determined, which consists in determining the state by its input impedance. This step is performed in two stages. In the first stage, based on the state of the track relay, the fact that the track circuit doesn't work in normal mode is verified. In the second stage, the shunt mode is separated from the control mode by the value of the track circuit input impedance. In the shunt mode of the track circuit operation, the coordinate and, if necessary, the speed and acceleration of the moving unit located within the given track circuit are determined. In the normal mode of the track circuit line operation, the values of its secondary parameters are specified based on the measured values of current, voltage, and phase shift between them. This operation is performed to increase the precision of the speed and acceleration determination by solving an inverse problem. In the control mode of the track circuit operation, it is possible to determine the coordinates of damage. This method does not require a significant volume of calculations. It makes it possible to determine the secondary parameters of the track circuit and through them, the resistance of its insulation. Using this method makes it possible to determine the distance and, if necessary, the speed and acceleration of a moving unit within the track circuit. The resulting parameters can be used for positioning moving rolling stock on runs between stations. The application of this method can also be useful in sections of the railway crossings approach to implement a fixed warning time. In addition, thanks to the use of the outlined model, in the control mode of the track circuit operation, is possible to determine the damage coordinate. It will make it possible to reduce the time spent on damage detection and elimination.

A Current-Limiting Scheme for Voltage-Controlled Inverter Using Instantaneous Current to Generate Virtual Impedance

In this paper, a current-limiting scheme is proposed for the voltage-controlled inverter. The method utilizes instantaneous current to quickly activate a resistive fault-current-limiting virtual impedance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FCL</sub> ) to suppress the instantaneous impulse current and steady-state overload current, which can be directly integrated into the existing voltage-type control scheme. When a fault occurs, the inverter can be kept in the voltage control mode without mode switching. After the fault is cleared, it can automatically return to the normal operation mode. The parameter selection method of the current-limiting virtual impedance is analyzed, and the logic criterion for short-circuit fault clearance is presented to realize the automatic startup and exit of the current-limiting virtual impedance. Finally, the RT-LAB hardware in-loop experiment and the single-phase inverter platform experiment prove that the proposed current-limiting scheme can simplify the fault handling process and improve the anti-fault ability of the voltage-controlled inverter.

Правовые аспекты обеспечения прав титульного владельца газопровода при выполнении работ на чужих земельных участках

This article is dedicated to a complex study of the issues of protection of rights of title gas pipeline holders (gas pipeline owners and gas pipeline operating companies) in performance of engineering works on gas transmission network sections located within the boundaries of land plots owned by others. Considering the special nature of a gas transmission network as a source of increased danger and a hazardous industrial facility, the author believes that one of the priority areas of gas pipeline operation is regular diagnostics and maintenance as well as in-process current (emergency) repair performed to avoid any breakdowns of the normal operation mode of the gas transmission network and causing of damage to lives, health and property of third parties. Taking into account these circumstances and the specifics of legal regulation of gas pipeline operation, the author of the article singles out the legal problem that lies in the ambiguity of approaches to the solution of the issue of provision of the title gas pipeline holder with access to the operated section of the gas transmission network if such facility is located within the boundaries of a land plot not owned by the gas pipeline holder. In order to solve this problem, the author performs a systemic analysis of the applicable laws of the Russian Federation and the legislative practice of some foreign countries and singles out three key concepts of provision of access to a gas pipeline located at a land plot owned by another person; such concepts include an opportunity to establish private or public easement and imperative proclamation of the unconditional right of the gas pipeline holder to unrestricted access to any section of the operated gas transmission network irrespective of the ownership of land plots such sites are located at. The author gives a systemic evaluation of each of the mentioned conceptual approaches; based on such evaluation, the author brings forward recommendations for improvement of the applicable laws to comply with the proclaimed principle of ensuring energy security of the Russian Federation.

A chip activation protocol for preventing IC recycling

Penetration of recycled integrated circuits into electronic components’ supply chain has been a major concern in recent decades. Due to shorter lifetime compared to original counterparts, deploying recycled components into electronic products can cause potential reliability and performance issues, apart from economic loss for the chip manufacturers. Current countermeasures proposed for addressing IC recycling can only detect counterfeit components, but cannot prevent them from entering into the supply chain, yet no prevention approach has been introduced for this purpose. In this paper, a chip activation protocol is proposed which, once approved and standardized among chip manufacturers, can actively protect ICs against recycling attacks. In this approach, each integrated circuit performs a simple and lightweight authentication procedure and enters into its normal operation mode only when the authentication procedure succeeds. Recycled ICs would be non-functional due to failed authentication. Experimental results on a 32-bit microprocessor reveal that the proposed approach incurs low overhead to the chip area, while imposing zero timing overhead to the normal operation of the chip.

Design methodology of intelligent autonomous distributed hybrid power complexes with renewable energy sources

The paper proposes a methodology for designing intelligent systems of autonomous distributed hybrid power complexes (ADHPC) ensuring a minimum level of energy consumption from the national external grid as well as diesel power plants used to deliver the power to regional households, and industrial consumers. It will be realized because of the effective use of generated energy from renewable energy sources in such ADHPC systems by considering their both normal and emergency operating modes. In doing so, ADHPC will not only help offload the existing power grid during peak demand, but also allow for significant process efficiencies in energy production from renewable energy sources (RES), including “green” hydrogen: for instance, the excess energy is accumulated during the period of its excess and is provided back to power consumers in the period of shortage, the electricity losses are reduced since effective management is applied for power flows circulating in the ADHPC systems. The methodology includes the following stages (subtasks): development of the structure of a distributed hybrid system for generating and transporting electricity from sources to consumers; development of a system for diagnostics of failures of generating units and wire breaks in sections of local power transportation networks and management based on the diagnostics results of power flows circulating in the ADHPC systems for both normal and emergency modes. Therefore, a balance of power capacities and minimization of their losses are ensured.

The transient instability mechanism and stability‐enhanced LVRT control for VSC riding‐through severe grid voltage sag

AbstractAs the grid‐connected interface device of wind and photovoltaic power generation, the voltage source converter (VSC) must pass the low voltage ride‐through (LVRT) test. However, existing literature demonstrates that under weak grid conditions, there is a possibility of severe fluctuations in the terminal voltage of VSC during transiting from the pre‐sag normal operation mode to the LVRT mode. Unfortunately, it will make VSC frequently enter and exit LVRT mode. In order to address the tricky problem of transient instability of VSC riding‐through severe grid voltage sag under the weak grid, in this paper, the full‐order large‐signal model of VSC is established first. Then, based on the established model, the analysis indicates VSC will face the risk of losing stability under the weak grid during LVRT due to current transients. By studying the impacts of low short circuit ratio (SCR) on the basin of attraction of the post‐sag equilibrium point, the intrinsic mechanism of VSC losing stability under weak grid conditions is revealed. Moreover, considering that the transient stability is related to the current control, the stability‐enhanced LVRT control ensuring both small‐signal stability and transient stability of VSC during LVRT is proposed. Finally, the correctness of the above theoretical analysis is verified by real‐time simulation

Study of Electromagnetic and Thermal Transients in a High-temperature Superconducting Transformer during a Short Circuit

Today, high-temperature superconducting (HTS) current limiters and transformers allow to limit the surge short circuit current during failure without negatively affecting on the power grid complex at the normal operation mode. However, the transition of a superconductor to a resistive state at the moment of current limitation can cause significant heat generation, which can destroy the transformer windings. The research goal is to provide optimal technical characteristics of the HTS transformer to achieve effective short circuit current limitation and prevent thermal breakdown of its windings. To achieve this goal, a mathematical model of a HTS transformer was developed. The presented method considers the material type and geometry of the superconducting tape, the critical parameters of the superconductor (current and temperature), the parameters of the cryogenic liquid, dependence of the resistance and heat capacity of the HTS tape layers on temperature. The simulation model was created in the Matlab/Simulink software. The most important result is the possibility of obtaining optimal electrical and thermal parameters of the HTS transformer windings during the short circuit current limitation, as well as ensuring the thermal stability of the superconducting tape at the quench moment. The obtained results are significant in the design and operation of HTS transformers. For efficient and safe operation in the current-limiting mode, it is necessary to take into account heat generation on the transformer windings. It is important for the superconductor returning to the superconducting state without causing significant overheating of the windings.

Formulation Analysis and Follow-Up Study of Differential MEMS Touch-Mode Sensor Utilizing Capacitive Vacuum Gauge Framework for Low-Pressure Measurements

Differential capacitance diaphragm gauges have become more popular in pressure measurements as they yield superior sensitivity and lesser non-linearity for pressure differential measurements. In addition, differential capacitance diaphragm gauges do not require a high vacuum reference cavity which reduces their manufacturing complexity. Efficient analysis for modelling differential capacitance diaphragm gauges is thus increasingly becoming vital due to their innumerable use cases. The higher sensitivity of circular diaphragm for the same side length in comparison to square diaphragm makes it ideal for sensor design. In this work, a complete formulation for analysis of differential capacitive vacuum gauge with the circular diaphragm in normal and touch mode operation has been presented for the low-pressure range of (1 to 1500 pascals). A comprehensive study of sensor parameters like capacitance, diaphragm deflection, capacitive and mechanical sensitivity has been formulated to aid the choice of sensor characteristics. Computationally complex methods have been used in the past for analysis of circular diaphragms. MATLAB and COMSOL have been used to compute and simulate results.

Research on the Impact of COVID-19 on All Walks of Life and Countermeasures

Since the sudden outbreak in 2019, COVID-19 has had a great impact on the whole social economy. By analyzing the specific reasons for the blow or promotion of all industries, This paper discuss the specific countermeasures to promote the future development of the industry. Research shows that the impact of the COVID-19 on tourism and catering industry is rapid and destructive. But it has a significant role in promoting the Internet industry. Today, when the epidemic situation is gradually stabilized and normalized, enterprise managers can no longer imagine returning to the normal operation mode, and should actively reform to adapt to the stable development of the overall environment. For some industries that are currently enjoying the dividends brought by the epidemic, they should be soberly aware of the strength of their products, analyze the actual growth rate brought by the epidemic and make plans for long-term development.

Zero-Sequence Current Suppression Method for Fault-Tolerant OW-PMSM Drive With Asymmetric Zero-Sequence Voltage Injection

For the open winding permanent magnet synchronous motor (OW-PMSM) with leg open-circuit faults, a novel zero-sequence current (ZSC) suppression method with asymmetric zero-sequence voltage (ZSV) injection is proposed in this article. To realize the fault-tolerant control (FTC) in leg open-circuit fault conditions, the leg-sharing method is developed, where the output terminal of the faulty leg is connected to that of the remaining equivalent leg. However, the ZSC increases in the FTC mode, which causes severe torque ripple and system performance degradation. If the traditional ZSC suppression method is still adopted, the suppression performance is decreased. Besides, an undesired voltage vector is introduced, resulting in current distortion. To solve these problems, a novel ZSC suppression strategy is put forward. By asymmetrically adjusting the voltage output of the remaining legs, the ZSC of OW-PMSM in FTC mode can be effectively suppressed. Moreover, the proposed strategy is suitable for both the single-leg and double-leg FTC modes, where the ZSC suppression performance is almost the same as that of the traditional method in normal operation mode. Furthermore, experiments are performed on an OW-PMSM to verify the effectiveness of the proposed ZSC suppression scheme.