HerMES: Current Cosmic Infrared Background Estimates Can be Explained by Known Galaxies and their Faint Companions at z < 4

We report contributions to cosmic infrared background (CIB) intensities originating from known galaxies and their faint companions at submillimeter wavelengths. Using the publicly-available UltraVISTA catalog, and maps at 250, 350, and 500 {\mu}m from the \emph{Herschel} Multi-tiered Extragalactic Survey (HerMES), we perform a novel measurement that exploits the fact that uncatalogued sources may bias stacked flux densities --- particularly if the resolution of the image is poor --- and intentionally smooth the images before stacking and summing intensities. By smoothing the maps we are capturing the contribution of faint (undetected in K_S ~ 23.4) sources that are physically associated, or correlated, with the detected sources. We find that the cumulative CIB increases with increased smoothing, reaching 9.82 +- 0.78, 5.77 +- 0.43, and 2.32 +- 0.19$\, \rm nW m^{-2} sr^{-1}$ at 250, 350, and 500 {\mu}m at 300 arcsec FWHM. This corresponds to a fraction of the fiducial CIB of 0.94 +- 0.23, 1.07 +- 0.31, and 0.97 +- 0.26 at 250, 350, and 500 {\mu}m, where the uncertainties are dominated by those of the absolute CIB. We then propose, with a simple model combining parametric descriptions for stacked flux densities and stellar mass functions, that emission from galaxies with log(M/Msun) > 8.5 can account for the most of the measured total intensities, and argue against contributions from extended, diffuse emission. Finally, we discuss prospects for future survey instruments to improve the estimates of the absolute CIB levels, and observe any potentially remaining emission at z > 4.Comment: Accepted to ApJL. 6 Pages, 3 figure

Origins and Impacts of High-Density Symmetry Energy

What is nuclear symmetry energy? Why is it important? What do we know about it? Why is it so uncertain especially at high densities? Can the total symmetry energy or its kinetic part be negative? What are the effects of three-body and/or tensor force on symmetry energy? How can we probe the density dependence of nuclear symmetry energy with terrestrial nuclear experiments? What observables of heavy-ion reactions are sensitive to the high-density behavior of nuclear symmetry energy? How does the symmetry energy affect properties of neutron stars, gravitational waves and our understanding about the nature of strong-field gravity? In this lecture, we try to answer these questions as best as we can based on some of our recent work and/or understanding of research done by others. This note summarizes the main points of the lecture.Comment: Invited lecture given at the Carpathian Summer School of Physics 2016, Exotic Nuclei and Nuclear Astrophysics (VI), Sinaia, Romania, June 26 to July 9, 201

Identification of Two-Mass Mechanical Systems Using Torque Excitation: Design and Experimental Evaluation

This paper deals with methods for parameter estimation of two-mass mechanical systems in electric drives. Estimates of mechanical parameters are needed in the start-up of a drive for automatic tuning of model-based speed and position controllers. A discrete-time output error (OE) model is applied to parameter estimation. The resulting pulse-transfer function is transformed into a continuous-time transfer function, and parameters of the two-mass system model are analytically solved from the coefficients of this transfer function. An open-loop identification setup and two closed-speed-loop identification setups (direct and indirect) are designed and experimentally compared. The experiments are carried out at nonzero speed to reduce the effect of nonlinear friction phenomena on the parameter estimates. According to results, all three identification setups are applicable for the parameter estimation of two-mass mechanical systems.Peer reviewe

Power source electronic ballast for electrodeless fluorescent lamps

This paper presents the design, control strategy and experimental results of a two-step, power factor correction stage (PFC) and resonant inverter (RI), electronic ballast proposal to supply 150 W electrodeless fluorescent lamps (EFL). The PFC acts as a controlled power source and provides mid and long-term stability to the system, while the stability of the current through the lamp is achieved with the RI. In addition, the power-mode control requires limitation of the output voltage. The dual operation mode of the PFC (voltage source mode and power source mode) enables an e cient soft resonant ignition and the implementation of simple dimming regulation.This work has been supported by the Spanish Ministry of Science and Innovation and the EU through the projects CICYT-FEDER-TEC2014-52316-R: “Estimation and Optimal Control for Energy Conversion with Digital Devices, ECOTRENDD” and RTI2018-095138-B-C31 PEGIA: “Power Electronics for the Grid and Industry Applications”

All-Electric Ship Design: From Electrical Propulsion to Integrated Electrical and Electronic Power Systems

Electrical propulsion is not a novel concept in marine systems. However, the availability of power electronic converters has proved to be the Key Enabling Technology for electrification of large ships. This paper starts with a summary of EP drives, which led to the birth of all-electric ships. Electric power generation and control systems are then presented, which make it possible to exploit the integrated electrical power system. To ease comprehension of the issues in designing such a system, its conventional design process is given. Then, the reasons that are pushing ahead the research in the shipboard power systems sector are discussed. The need for research in the design methods area is demonstrated through an overview of the latest results of technological research. Finally, a summary of the most significant results on the design tools research is given, including early stage design, dependable-oriented design, and the improvements achievable through software simulators and hardware-in-the-loop are discussed. The goal of this paper is to demonstrate why research on design methods is as important as a technological one, on the basis of the needs concerning the design, integration, and management of future 'integrated electrical and electronic power systems' (power systems with power conversion quota approaching 100%)

Разработка усовершенствованной методики расчета параметров фильтрокомпенсирующих цепей статического тиристорного компенсатора электродуговой печи

Relevance. A lot of Russian as well as foreign metallurgical feature electrical steel-mashing complexes based on electric arc furnaces (EAF) and ladle furnaces (LF). These steel-making units generate high-power electrical load, have non-linear volt-ampere characteristics and leaping unbalanced load variation. For this reason, an operating EAF aggravates power quality and causes an increase in the reactive power factor on the incoming feeders of the main electrical substations. To provide for the appropriate power quality and voltage stabilization on the primary side of the furnace transformer, the additional reactive power compensation devices are used. More than 85% of reactive power compensators for EAF and LF are currently released as static var compensators consisting of a thyristor- controlled reactor (TCR) and filter circuits (FC). The analysis of the rated parameters of SVC produced by different companies shows that there is no universal selection method for the harmonic filters configuration. In that regard, a pressing task is to develop a complex approach to determine an optimum configuration of harmonic filters, provided that its their rated power is known. Research objective: developing the improved method used to select the parameters of filter circuits of SVC for electric arc furnace, accounting for different relevance criteria such as: the cost of FCs, active power losses in harmonic filters, filtration coefficient, and the total harmonic distortion of voltage. Methods: experimental arrays of electrical parameters saved on existing electrotechnical complexes “EAF-SVC” and the methods of mathematical modeling of SVC and EAF. Novelty: the suggested developed method of SVC’s filter circuits parameters selection is original as it features the distribution of the total reactive power using the group optimal criteria, which provides for the best technical and economical indexes of FC, as well as accounting for the peculiar features of a certain steel-making unit and its power supply system. This method is also more accurate in terms of analysis of the electrical regimes of FC as it uses real instantaneous current of EAFs of different classes and power. Research outcomes: 1) the executed analysis of parameters of existing SVC produced by different companies; 2) the existing methods of distribution of total reactive power between harmonic filters have been analyzed; 3) the improved mathematical model of complex “EAF-SVC” allowing for the detailed studies of FC operation modes taking into account the real EAF’s current been mode; 4) the patterns of variation of filtration coefficient for different variants of distribution of total reactive power between harmonic filters have been determined on the basis of mathematical model; 5) the improved method of calculation of SVC’s FC providing for the optimum distribution of reactive power between the harmonics filters taking into account a group of different optimal criteria has been developed. Practical significance: the results have significant theoretical importance for electrical engineering of arc furnaces and may be employed in the calculation of static var compensators in power supply systems of steel-making complexes.В настоящее время большое количество металлургических заводов в России и за рубежом имеют в своем составе электросталеплавильные комплексы на базе дуговых сталеплавильных печей (ДСП) и установок ковш-печь (УКП). Данные агрегаты являются мощными электроприемниками с нелинейной вольтамперной характеристикой и резкопеременным, несимметричным характером изменения нагрузки, поэтому при работе печи наблюдаются нарушения показателей качества электрической энергии и повышение коэффициента реактивной мощности на границе балансовой принадлежности предприятия и внешней питающей сети. Для улучшения показателей качества электрической энергии и обеспечения стабилизации напряжения в точке подключения печного трансформатора электродуговой печи дополнительно применяют устройства компенсации реактивной мощности. На сегодняшний день более 85 % от общего количества компенсирующих устройств для ДСП и УКП используют статический тиристорный компенсатор (СТК), состоящий из тиристорно-реакторной группы и фильтров высших гармоник. Анализ номинальных параметров СТК различных фирм-производителей показал отсутствие универсальной методики выбора параметров фильтрокомпенсирующих цепей (ФКЦ) компенсаторов. В связи с этим актуальной задачей является разработка комплексного подхода определения оптимальной конфигурации фильтров высших гармоник при их известной суммарной мощности. Цель работы – разработка усовершенствованной методики выбора параметров ФКЦ СТК электродуговой печи, учитывающей различные критерии оптимальности, такие как стоимость ФКЦ, потери активной мощности в фильтрах высших гармоник, коэффициент фильтрации, суммарный коэффициент гармонических составляющих напряжения. Используемые методы: для проведения исследований использовались экспериментальные массивы электрических параметров, полученные на действующих электротехнических комплексах «ДСП-СТК», а также известные методы математического моделирования электродуговых печей и СТК. Новизна: разработанная методика расчета параметров фильтрокомпенсирующих цепей СТК отличается от известных тем, что распределение мощности между фильтрами высших гармоник осуществляется с использованием группы критериев оптимальности, что позволяет достичь наилучших технико-экономических параметров ФКЦ с учетом особенностей конкретного электросталеплавильного агрегата и его системы электроснабжения. Данная методика обладает повышенной точностью анализа электрических режимов ФКЦ за счет возможности использования реальных токов электродуговых печей разного класса и мощности. Полученные результаты: 1) выполнен анализ параметров действующих СТК различных фирм-произ­водителей; 2) проанализированы существующие методики распределения мощности между фильтрами; 3) разработана усовершенствованная математическая модель комплекса «ДСП-СТК», позволяющая проводить детальные исследования режимов работы ФКЦ СТК с учетом реального гармонического состава токов ДСП; 4) на основании математической модели установлены закономерности изменения коэффициента фильтрации ФКЦ при различных вариантах распределения суммарной мощности между фильтрами; 5) разработана усовершенствованная методика расчета параметров ФКЦ СТК, обеспечивающая оптимальное распределение мощности между фильтрами высших гармоник с учетом совокупности различных критериев оптимальности. Практическая ценность: полученные результаты исследований имеют большую практическую значимость при проектировании и расчете параметров фильтрокомпенсирующих цепей СТК, функционирующих в системах электроснабжения электросталеплавильных комплексов

Modeling and Experimental Verification of Adaptive 100% Stator Ground Fault Protection Schemes for Synchronous Generators

Salient pole synchronous generators as the main component of an electricity generation station should be carefully maintained and their operation has to be monitored such that any damage on them is avoided. Otherwise, the generating station might experience frequent shut downs which results in electricity generation interruptions and high costs associated with repairing and compensation of lack of energy. In this sense, many protective schemes focusing on a variety of synchronous generator faults have already been proposed and are still modified and developed to further enhance the quality of protection. In this thesis, synchronous generator stator windings to ground fault is studied as one of the most common and crucial faults in these machines. Numerous methods of stator winding to ground fault protection schemes are also reported in the literature. Third harmonic differential voltage and sub-harmonic schemes are studied in this research. A novel adaptive scheme for both methods is modelled and implemented in a comprehensive lab scale set-up where a real generation unit is scaled down including all different components and apparatus. The simulation model is also established based on simultaneous finite element analysis (FEA) and coupled magnetic circuit to assist with system configuration design and parameter selections. The adaptive scheme is proved to be capable of detecting stator windings to ground faults based on actual experimental data. Finally, the proposed adaptive scheme is compared against other available non-adaptive protection schemes currently used in industrial relays. Several important performance evaluation criteria in protection schemes such as sensitivity and security of operation referred to as reliability are considered. It is shown that the adaptive scheme offers higher reliability than other schemes which emphasizes its credibility and applicability

Управление устройством РПН сетевого трансформатора с учетом режимов работы электросталеплавильного комплекса

The paper presents the main results of developing and researching a new principle for controlling the step-down transformer on-load tap changer (OLTC), which coordinates the OLTC operation with the electrical parameters of the electric-arc steelmaker, compensators installed in the high-power and ultrahigh-power EAF power supplies, and the mains. The proposed principle consists in pre-determining the operating voltage ranges on the mains-transformer primary side for all OLTC tap positions taking into account the existing of both the electric-arc steelmaking facility and the mains. The static VAR compensator (SVC) control system is improved by adding a block for finding the mains-transformer OLTC tap position number so as to use new position-switching algorithms. The problem of optimizing the OLTC tap-position switching in mains-transformers supplying power to electric-arc steelmaking facilities under significant mains-voltage deviations is analyzed on the basis of evidence from three Russian steelworks companies. We herein discuss the particularities selecting the mains-transformer OLTC positions in two SVC control modes, one consisting in keeping zero consumption of reactive power from the mains, and the other one consisting in maintaining a coordinate voltage in the common EAF and SVC connection point. The effect of the proposed solutions is found from the results obtained by means of mathematical modeling of electric-arc steelmaking facilities in MATLAB Simulink. We discuss the options for further improvement of principles for coordinating the operation of automatic transformer-voltage regulators (AVR) with the parameters of steelmakers, compensators, and mains.Приведены основные результаты разработки и исследования нового принципа управления устройством регулирования напряжения трансформатора под нагрузкой (РПН), который обеспечивает согласованную работу последнего с электрическими режимами сталеплавильных агрегатов, компенсирующих устройств, устанавливаемых в системе электроснабжения дуговых печей (ДСП) высокой и сверхвысокой мощности, и питающей сети. Предложенный принцип заключается в предварительном определении рабочих диапазонов напряжений на первичной стороне сетевого трансформатора для всех ступеней РПН с учётом существующих ограничений как со стороны электросталеплавильного комплекса, так и со стороны питающей сети. Для реализации переключений ступени РПН по новым алгоритмам проведено усовершенствование системы автоматического управления статического тиристорного компенсатора (СТК) путем ее дополнения блоком определения номера ступени РПН сетевого трансформатора. Проведен анализ проблемы рационального переключения ступеней РПН сетевых трансформаторов, питающих электросталеплавильные комплексы, в условиях сильных отклонений напряжения в питающей сети на примере трех российских металлургических предприятий. Рассмотрены особенности выбора положений РПН сетевых трансформаторов при двух режимах управления СТК: обеспечение нулевого потребления реактивной мощности из питающей сети и поддержание уровня напряжения в точке общего подключения дуговых печей и СТК на согласованном уровне. Эффект от предложенных решений определен на основе результатов, полученных с помощью математических моделей электросталеплавильных комплексов, разработанных в приложении Simulink математического пакета MATLAB. Рассмотрены пути дальнейшего совершенствования принципов согласованного функционирования устройства автоматического регулирования напряжения трансформатора (АРНТ) с режимами сталеплавильных агрегатов, компенсирующих устройств и питающей сети