Dynamic Mode Of Operation Research Articles

Toward developing accelerated stress tests for proton exchange membrane electrolyzers

Abstract Proton exchange membrane water electrolysis is technically the most suitable technology for the production of green hydrogen on a large scale. Although it is still more expensive than hydrogen produced from fossil sources, it has already been commercialized. Novel components with cost-effective materials and efficient manufacturing processes are being rapidly developed. However, these components must endure durability tests that can guarantee a lifetime of at least 50,000 operation hours. Consequently, there is an urgent need to develop accelerated stress test protocols based on a deep understanding of degradation mechanisms of stack components. Recent reports show that the main degradation mechanisms are associated to anode catalyst dissolution, membrane chemical decomposition, and formation of semiconducting oxides on the metal components. These mechanisms can be accelerated by stressors such as high current density, dynamic operation, and shutdown modes. On the basis of these reports and knowledge of the operational requirements for large-scale proton exchange membrane water electrolysis, we propose an accelerated stress test protocol for the fast evaluation of newly developed cost efficient and durable components.

Influence of External Electric Circuits on the Static and Dynamic Mode of Operation of Multipath Collectors of Powerful Klystrons

Abstract—The article considers the influence of external electric circuits on the work of the collector zone with an nonstationary intense electron beam. It is shown that the presence of capacitance of the collector and inductance of the external circuit under certain conditions can lead to the appearance of large inhibitory voltage values and deterioration of the klystron output parameters. The results of experimental studies are presented.

Development of a Decision-Making Framework for Distributed Energy Systems in a German District

The planning and decision-making for a distributed energy supply concept in complex actor structures like in districts calls for the approach to be highly structured. Here, a strategy with strong use of energetic simulations is developed, the core elements are presented, and research gaps are identified. The exemplary implementation is shown using the case study of a new district on the former Oldenburg airbase in northwestern Germany. The process is divided into four consecutive phases, which are carried out with different stakeholder participation and use of different simulation tools. Based on a common objective, a superstructure of the applicable technologies is developed. Detailed planning is then carried out with the help of a multi-objective optimal sizing algorithm and Monte Carlo based risk assessment. The process ends with the operating phase, which is to guarantee a further optimal and dynamic mode of operation. The main objective of this publication is to present the core elements of the planning processes and decision-making framework based on the case study and to find and identify research gaps that will have to be addressed in the future.

A Digital Readout IC for Microbolometer Imagers Offering Low Power and Improved Self-Heating Compensation

This paper presents a novel and power efficient readout architecture for uncooled microbolometers that offers adequate noise performance along with a circuit-based method for self-heating compensation. The proposed method employs an event-generation scheme and a time-mode readout chain to achieve dynamic mode of operation resulting in low power. The readout chain consists of a capacitive transimpedance amplifier (CTIA) based current-to-time converter followed by a two stage time-to-digital converter (TDC). The CTIA employs a novel integration scheme for time amplification along with a modified reset mechanism to achieve self-heating compensation. We also present a model to analyze the implications of time-mode readout on imager operation. An experimental readout chip, based on this approach, has been designed using a 130 nm bulk CMOS technology. The proposed architecture offers robust frontend processing and achieves a per channel power consumption of $66~\mu \text{W}$ , which is considerably lower than the most recently reported designs, while maintaining better than 10-mK readout noise equivalent temperature difference (NETD).

Energy-efficient predictive control for field-orientation induction machine drives

Purpose. To improve the efficiency of the closed-cycle operation of the field-orientation induction machine in dynamic behavior when load conditions are changing, considering the nonlinearities of the main inductance. Methodology. The optimal control problem is defined as the minimization of the time integral of the energy losses. The algorithm observed in this paper uses the Matlab/Simulink, dSPACE real-time interface, and C language. Handling real-time applications is made in ControlDesk experiment software for seamless ECU development. Findings. Adiscrete-time model with an integrated predictive control scheme where the optimization is performed online at every sampling step has been developed. The optimal field-producing current trajectory is determined, so that the copper losses are minimized over a wide operational range. Additionally, the comparison of measurement results with conventional methods is provided, which validates the advantages and performance of the control scheme. Originality. To solve the given problem, the information vector on the current state of the coordinates of the electromechanical system is used to form a controlling influence in the dynamic mode of operation. For the first time, the formation process of controls has considered the current state and the desired future state of the system in the real-time domain. Practical value. Apredictive iterative approach for optimal flux level of an induction machine is important to generate the required electromagnetic torque and to reduce power losses simultaneously.

Parametric Optimization of Electrohydraulic Servo System

The electrohydraulic servo systems used in the industrial production are characterized by relatively simple construction, easy operation and high speed, good reliability, functional flexibility and low cost. All this demonstrates the need to study the performance of electrohydraulic servo system primarily in dynamic operating modes. The article studies a mathematical model of electrohydraulic servo system with the typical nonlinearities. The parametric optimization of the automatic PID controller was performed on the basis of minimizing the integral quality criterion when comparing reference and experimental transient processes. The obtained results are shown in a graphical form.

IMPLEMENTATION OF THE FUNCTIONS OF MANAGEMENT WITHIN THE SYSTEM OF STRATEGIC CORPORATE FINANCE MANAGEMENT

Objective. The objective of the article is to summarize the theoretical insights into strategic corporate finance management through the implementation of the functions of management. Methods. To achieve the goal, methods of theoretical generalization, analysis and synthesis, logical generalization, analogy method, the methods of comparative analysis andformal and con­ceptual modeling are used. Results. As a result of the research, certain tasks have been performed and an attempt to formalize the content of the strategic corporate finance management process by the method of formal and conceptual modeling has been made. As a result, a model of the strategic corporate finance management system in the context of dynamic operation mode has been developped. The model presented contains input flows — the components of the enterprise financial assets — and output flows (final state of the system). The difference between the obtained formal and concep­tual model and the Black Box model is the information about the content of processes occurring within the organization to ensure the final state of the system (output flows). The final state of the system is assessed by the relevant indices of financial standing, financial solvency, business effi­ciency, business activity. The criterion values of the final state of the system are achieved through the implementation of appropriate corporate finance management strategies (asset management, capital management, investment management, cash flow management, financial risk management, financial crisis management) and the implementation of the functions of management (planning, organization, motivation and control).

Численное моделирование динамического режима работы линейного электромагнитного двигателя лабораторного шеикера

The design of the laboratory shaker linear electric drive mechanical part is proposed, its mathematical model is given, and the algorithm for calculating the linear electromagnetic motor’s dynamic characteristics is presented. Computer simulation of the drive is carried out using the COMSOL Multiphysics finite element modeling software. The dynamic operation mode of the motor’s reciprocating motion is studied, and its dynamic (speed-torque) characteristics are given. The study results have shown that the laboratory shaker drive based on a linear electromagnetic motor has properties commensurable with those of the drive for serially produced shakers. Moreover, in regard of certain indicators, such as the maximum oscillation frequency and peak power consumtion, the newly designed drive has better characteristics.

Three Multiterminal Silicon Power Chips for an Optimized Monolithic Integration of Switching Cells: Validation on an H-Bridge Inverter

This article deals with the monolithic integration in silicon of a multiphase static power converter (dc/ac or ac/dc) for medium power applications, from few kilowatts to few tens of kilowatts with power devices’ blocking capability in the range of 600–1200 V. This article presents an original three-chip integration approach that combines both monolithic integration in silicon and printed circuit board (PCB) packaging process and takes advantage of both silicon-level technology and PCB-level technology within a limited and well-mastered complexity. The converter is integrated within only three new multiterminal power chips, which are then judiciously packaged on a PCB so as to minimize the switching cell stray inductance and the impact of voltage variations ( dv / dt ) across the common-mode stray capacitance of the assembly. The static and the dynamic operating modes of the proposed multiterminal power chips were validated using 2-D-Sentaurus TCAD simulations. The realized chips were packaged on a PCB to realize both classical and three-chip-based H-bridge inverters. First characterization results validate the electrical operating modes of the H-bridge inverter realized according to the three-chip approach.

Method for control of the start-up regulating devicefor power transformers of the power supply system

Three-phase thyristor switches are designed for pulsed formation of inrush currents of electrical equipment with their subsequent shunting in steady state operation. In transformer substations, they perform a bumpless turning on of a power transformer by connecting its primary winding first to two phases of the network at the moment of zero crossing by the phase voltage of the network third phase, and then to the network third phase at the moment of zero crossing by the line voltage of the other two network phases. In this case, the starting currents of the transformer almost immediately enter the steady state without the appearance of constant components in the magnetization currents and voltage drop. To expand the functionality of thyristor switches, it is proposed, in addition to bumpless turning on of a power transformer, to disconnect it without arcing between the contacts of electrical equipment, as well as to carry out continuous voltage regulation for consumers when voltage in the network changes. The proposed method and structure for its implementation on the basis of two three-phase thyristor reactor keys and a capacitor bank make it possible while changing the network voltage to stabilize the generated reactive power at the input of the substation without creating the current distortions in the power transformer and power transmission simultaneously with stabilizing the substation output voltage. Modeling and research of the start-regulating device as part of a transformer substation was carried out in the MatLab environment. The results of numerical experiments in stationary and dynamic modes of the substation operation showed the feasibility of using the developed technical solutions for the industrial power supply system.

Parallel power active filter new control technique based on modified p-q-r power theory

The paper presents the main advantages of using the instantaneous p-q-r power theory to construct high-speed control system for power active filters. It allows to realize both quasi-static and dynamic modes of operation of electric energy consumers with active filter-compensating devices powered by a three-phase four-wire utility grid. At the same time, it has been shown that the use of p-q-r coordinate’s transformations is due to the large number of mathematical calculations performed by the microcontroller in real time and require a high degree of performance of the hardware part of the control system. A new technique for controlling parallel power active filter combining the universal p-q-r power theory with cross-vector theory is proposed. The proposed technique should be used in control systems of power active filters operating for three-phase four-wire electrical systems with electrical load of any type, as well as in hybrid systems, when the power part of the converter can be used not only as a filter-compensating device, but as a voltage inverter. It is shown that the use of the proposed technique can significantly reduce the number of mathematical calculations performed by the control system microcontroller for the implementation of control signals by power transistor modules. The Matlab model of a real power supply system with a parallel power active filter to test the efficiency of the algorithm is synthesized. Comparing the simulation results for the three power active filter control technique allowed to evaluate the quality of the proposed algorithm and to confirm not only its efficiency but also the equivalence of the received power characteristics to the characteristics that were obtained when using the universal p-q-r instantaneous power theory.

Computational fluid dynamics analysis on solar water heater: Role of thermal stratification and mixing on dynamic mode of operation

The present work attempts to demonstrate the competence and reliability of the proposed computational solver for real-scale modelling and analysis of a commercially available evacuated tube collector type solar water heater. A 3-D, transient numerical solver with user-defined functions is modelled using CFD program ANSYS-Fluent 15.0?. The objective is to analyse the evacuated tube collector type solar water heater in two states of operation, namely, static (stagnant charging) and dynamic (retrieval) modes. This work emphasizes the determination of the impact of thermal stratification, and fluid mixing in the storage tank on the outlet temperature profile during discharging. Volume flow rates vary from 3-15 Lpm. The reported findings suggest that with an increase of fluid-flow during discharge, the stratified layers disorient and lead to rapid mixing, which eventually results in an earlier drop in the outlet water temperature. Furthermore, at low fluid-flow rates, the stratified layers remain intact with only a gradual decay in the outlet temperature profile. The analysis reveals that based on the user?s choice, it is possible to vary discharge flow rate until 7 Lpm without a significant drop in the outlet water temperature. Furthermore, computational results have been successfully validated with experimental findings.

Control of MMC-Based STATCOM as an Effective Interface between Energy Sources and the Power Grid

This paper presents a dynamic model of modular multilevel converters (MMCs), which are considered as an effective interface between energy sources and the power grid. By improving the converter performance, appropriate reactive power compensation is guaranteed. Modulation indices are calculated based on detailed harmonic evaluations of both dynamic and steady-state operation modes, which is considered as the main contribution of this paper in comparison with other methods. As another novelty of this paper, circulating current control is accomplished by embedding an additional second harmonic component in the modulation process. The proposed control method leads to an effective reduction in capacitor voltage fluctuation and losses. Finally, converter’s maximum stable operation range is modified, which provides efficiency enhancements and also stability assurance. The proficiency and functionality of the proposed controller are demonstrated through detailed theoretical analysis and simulations with MATLAB/Simulink.

Impact of Fabric Properties on Textile Pressure Sensors Performance.

In recent years, wearable technologies have attracted great attention in physical and chemical sensing applications. Wearable pressure sensors with high sensitivity in low pressure range (<10 kPa) allow touch detection for human-computer interaction and the development of artificial hands for handling objects. Conversely, pressure sensors that perform in a high pressure range (up to 100 kPa), can be used to monitor the foot pressure distribution, the hand stress during movements of heavy weights or to evaluate the cyclist’s pressure pattern on a bicycle saddle. Recently, we developed a fully textile pressure sensor based on a conductive polymer, with simple fabrication and scalable features. In this paper, we intend to provide an extensive description on how the mechanical properties of several fabrics and different piezoresistive ink formulation may have an impact in the sensor’s response during a dynamic operation mode. These results highlight the complexity of the system due to the presence of various parameters such as the fabric used, the conductive polymer solution, the operation mode and the desired pressure range. Furthermore, this work can lead to a protocol for new improvements and optimizations useful for adapting textile pressure sensors to a large variety of applications.

ABOUT OF THE DYNAMICS OF FORCED OSCILLATIONS IN NONLINEAR SYSTEMS

The article discusses the issues of determining the effectiveness indicators of an electromagnetic vibration exciter in a dynamic mode of operation. It is established that this system is whole system of electrical and mechanical circuits. In this case, the mechanical part operates in the mode of forced vibrations. The oscillation parameters of the system, such as amplitude, frequency, and phase, largely depend on the parameters of the system load. For the analysis of this system, differential equations describing an electromagnetic vibration exciter have been compiled. For this purpose, the dependence L(x) of the inductance on the displacement is used. The dynamic modes of one of the ways of asynchronous excitation of an electromagnetic vibration exciter are investigated. The accuracy analysis and the evaluation of the results were performed by the Fisher criterion for the regression model. To analysis of transients in the electromagnetic vibration exciter, were used the software packages WinFact and MatLab to simulate and optimize dynamic systems. It is established that the system, depending on the initial conditions in the simulation, goes into one of two very different modes. In this case, the initial zero conditions switch the system into a “cyclic” mode, and in other, non-zero conditions, the system goes into an approximate cyclic mode, characterized by a higher speed of movement of the anchor. The parameters of the steady state cyclic movement are determined by the method of harmonic balance.&#x0D; The obtained results allow us to describe autoparametric oscillations of the electric equivalent circuit. It has been established that the compilation of harmonic balance equations corresponding to a linear system helps simplify the solution of the task of determining the dynamics of forced oscillations. The expressions for determining the tractive force and the current flowing through the circuit are obtained, the wavelet spectra of vibration are constructed using the MatLab software package. As a result, for the mechanical part of a nonlinear system, in fact, it is necessary to solve only harmonic balance equation. The results show that this theoretical model allows a more qualitative and accurate assessment of the observed phenomenon. Based on this, the asymptotic conditions for solving the harmonic balance equations of a nonlinear system are determined. The expressions for the electromagnetic force acting on the anchor are obtained, the conditions for the harmonic balance of the mechanical part of the system are determined. The expressions obtained allow us to construct the amplitude-frequency characteristics of the electromagnetic vibration exciter. In conclusion, not only qualitative, but also quantitative estimates of the observed phenomena were obtained. It has been established that mechanical oscillations of a nonlinear system are insensitive to changes in the supply network and practically have a large amplitude with a constant frequency.

AKUMULIACINĖS TALPYKLOS DINAMINIO VEIKIMO EKSPERIMENTINIS IR SKAITINIS TYRIMAS / EXPERIMENTAL AND NUMERICAL RESEARCH OF DYNAMIC OPERATION OF HEAT STORAGE TANK

Renewable energy sources (RES) and their transformation technologies become more attractive in building sector as energy demand and emissions to the environment increase. Along with renewable energy transformation technologies, the importance of energy storage also arises as these RES are characterized by volatility and energy mismatch over time. For this reason, engineering systems which use RES are becoming increasingly dynamic. This study examines ongoing processes in a vertical cylindrical storage tank designed to cover domestic hot water demand in a building. Simultaneous dynamic mode of operation when the energy is being charged and at the same time discharged from the storage tank is analysed. Experiments are performed and stratification number describing thermal stratification is calculated. The obtained data are used for the development and validation of the numerical model. Using Ansys Fluent software, the influence of different discharge rate on operation mode of the storage tank is investigated. Graphical and numerical interpretation of results is performed.

Dynamic beam current control for improved dose accuracy in PBS proton therapy

The step-and-shoot method of pencil beam scanning delivers the dose on a 3D grid in the target volume, with one dimension defined by the proton energy. While the dose per pencil beam may vary substantially within an iso-energy layer, the beam current typically remains constant. In this static operation mode, the inherent latency of the beam switch-off mechanism results in a lower limit for the deliverable spot dose, which may prevent the application of some of the low-weighted spots prescribed by the treatment planning system. To overcome this limitation, we introduced dynamic beam current control at the PSI Gantry 2, an innovative new approach successfully commissioned and in clinical operation since fall 2017. The control system was enhanced with a direct link to the vertical deflector located at the centre of the cyclotron. This connection allows much faster beam current changes (~0.1 ms) and hence opens up the possibility of dynamically reducing the current for individual low-dose spots. We demonstrate that with this new dynamic operation mode, all spots are delivered as planned without compromising treatment time. We show by two independent and complementary methods that the delivered dose distribution is improved.

Efficient & secure cipher scheme with dynamic key-dependent mode of operation

Security attacks are constantly on the rise leading to drastic consequences. Several security services are required more than ever to prevent both passive and active attacks such as Data Confidentiality (DC). A DC security service is typically based on a strong symmetric cipher algorithm. However, some of today’s applications, such as real-time applications and those running on constrained devices, require efficient lightweight cipher schemes that can achieve a good balance between the security level and system performance. Recently, a set of lightweight cryptographic algorithms has been proposed to that end, which is based on a dynamic key approach. The dynamic structure enables the reduction of the number of rounds to the minimum possible value of just one or two rounds, which minimizes the computational overhead without degrading the security level. This paper follows the dynamic key-dependent cipher logic and proposes a new flexible lightweight technique with or without the reliance on the chaining mode of operation. Furthermore, the dynamic key changes for each input message, which leads to different cipher primitives such as substitution and permutation tables, in addition to round keys. Also, the proposed mode of operation is based on the dynamic key approach whereby blocks are selected and mixed according to a dynamic permutation table. Accordingly, different plaintext messages are encrypted differently while preserving the avalanche effect. Finally, we conduct security and performance analysis to validate the efficiency and robustness of the proposed cipher scheme as compared to traditional ciphers and to the recently proposed dynamic key-dependent ciphers.

Method for Stabilizing the Operation of Synchronous Machines Using a Virtual Load Sensor

The article considers the methods of increasing the stability of high-power synchronous machines when stabilizing the torque angle in the structure of the automatic excitation control system. A mathematical model of an electric machine in open and closed automatic control systems is obtained, studies of electromagnetic processes and analysis of existing and proposed optimal control systems are carried out. A contactless sensor of torque angle of the synchronous motor based on measuring the available parameters of the synchronous machine and allowing us to calculate the torque angle in static and dynamic modes of operation of synchronous generator and compatible with the new control system was developed. The presented excitation control system of synchronous machine with a measuring sensor of torque angle that provides higher performance in dynamic modes, as well as allowing to stabilize the reactive power, the power factor and the voltage on the stator of the synchronous machine.

Selection of method for estimation of quality of asynchronous traction electric motors for elec-tric buses

Problem. Despite all the advantages of asynchronous electric motors (ADs), they often fail. In connection with this diagnosis of blood pressure in the production stage, during the acceptance tests and in the process of operation is one of the most important ways to improve the reliability and cost-effectiveness of equipment. Therefore, the right choice of diagnostic method for assessing the quality and technical condition at different stages of the life cycle of blood pressure is a guarantee of its reliable operation. This is especially true for traction BP, which operate in dynamic modes of operation of mechanical loads. Goal. The purpose of the work is to choose a method for assessing the quality of asynchronous traction electric motors for electric buses. Methodology. Analytical methods of theoretical studies, comparative analysis of methods for determining the quality of traction AO for electric bus are used. Results. A comparative analysis of existing methods for assessing the quality of asynchronous motors is carried out. Vibrant diagnostic characteristics were selected as criteria of quality assessment, in accordance with which it was suggested to use a vibration method for assessing the quality of tractional blood pressure for electric buses. Originality. The proposed method can be used at all stages of the life cycle of blood pressure: the stage of design, production, acceptance testing, operation and repair. In addition, this method uses dynamic parameters as diagnostic features, which is important for the operation of the traction electric motor in the city electric bus. Practical value. This work allows us to proceed to the next step - the development of the method of vibration diagnostics of blood pressure, which is planned to be lit in subsequent publications.Keywords: asynchronous motor; method of quality evaluation; electric bus; vibration characteristics; traction electric drive.