First-principles study on stability and magnetism of AlnZn (n=1-9) clusters

International Nuclear Information System (INIS)

Ren Xiaojun; Li Baoxing

2010-01-01

We have investigated the structures, stabilities and magnetism of zinc-doped Al n (n=1-9) clusters in detail by using first-principles density functional theory. Our calculated results indicate that the ground state structures of the mixed Al n Zn (n=1-9) clusters doped with one zinc atom can be obtained from the most stable structures of the pure Al n (n=2-10) clusters by substitutional type. The impurity atom causes local structural distortion due to different atomic radii and different bonding characteristics. It is found that the clusters with total atom numbers of 3 and 7 exhibit high stability. In addition, the energy gaps E g s between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) show obvious even/odd alternation with cluster size. Furthermore, we investigate the magnetism of the mixed clusters. The Al 4 Zn, Al 6 Zn and Al 8 Zn clusters with even number of electrons do not have any magnetism. All Al 1 Zn, Al 5 Zn, Al 7 Zn and Al 9 Zn clusters have the total magnetic moment of 1.0 μ B due to one unpaired electron. Unexpectedly, the Al 2 Zn and Al 3 Zn clusters show total magnetic moments of 2.0 and 3.0 μ B , respectively. The magnetism arises from the sp-d hybridization due to charge transfer and the influence of the impurity zinc atom.

α cluster structures in unbound states in 19Ne

Science.gov (United States)

Otani, Reiji; Iwasaki, Masataka; Ito, Makoto

2016-06-01

Cluster structures in 19Ne are studied by the microscopic and macroscopic cluster models. In the microscopic calculation, the coupled-channels problem of (3He+16O) + (α+15O) is solved, and the adiabatic energy surfaces, which are the series of the energy eigenvalues as a function of the He-O distance, are investigated. In the adiabatic energy curves, the several local minima are generated in the spatial region of the small core distance, where the neutron hole inside of the He or O nucleus is strongly coupled to the residual nuclei. The energy spectra, which are constructed from the strong coupling states, nicely reproduce the the low-lying energy levels in the 19Ne nucleus. In the macroscopic approach, the α + 15O potential is evaluated from the elastic scattering of the α + 15N system, and the resonant levels of the α + 15O system are calculated under the absorbing boundary condition. The potential model predicts the existence of the resonances above the α threshold, which has a weak-coupling scheme of the α particle and one hole inside of the 16O nucleus. The extended microscopic calculations of (3He+16O) + (α+15O) + (5He+14O) are performed in order to see the coupling effect of the 5p-2h configuration, which corresponds to the shell model limit of the 5He + 14O cluster configuration. The extended calculation suggests that the 5He + 14O configuration plays an important role on the formation of the 3/2+ resonance at 0.5 MeV with respect to the α threshold.

An experimental study of burnout and pressure drop in 19-rod clusters

International Nuclear Information System (INIS)

Edwards, P.A.

1976-03-01

This report presents experimental burnout and pressure drop data obtained from three 19-rod clusters, both wire wrapped and grid supported, and with both non-uniform and uniform radial heat flux. The clusters all had uniform axial heating, a heated length of 4 feet, and 5/8 in. diameters rods, though the rod spacings were somewhat different and only 18 rods were heated in the grid supported cluster. Tests were carried out in high temperature water/steam at 1000 psi flowing vertically upwards with a mass velocity of 0.5 x 10 6 to 2.5 x 10 6 lbs/ft 2 hr. (U.K.)

Expression of the Grape VaSTS19 Gene in Arabidopsis Improves Resistance to Powdery Mildew and Botrytis cinerea but Increases Susceptibility to Pseudomonas syringe pv Tomato DC3000.

Science.gov (United States)

Wang, Yaqiong; Wang, Dejun; Wang, Fan; Huang, Li; Tian, Xiaomin; van Nocker, Steve; Gao, Hua; Wang, Xiping

2017-09-17

Stilbene synthase (STS) is a key enzyme that catalyzes the biosynthesis of resveratrol compounds and plays an important role in disease resistance. The molecular pathways linking STS with pathogen responses and their regulation are not known. We isolated an STS gene, VaSTS19 , from a Chinese wild grape, Vitis amurensis Rupr. cv. "Tonghua-3", and transferred this gene to Arabidopsis . We then generated VaSTS19 -expressing Arabidopsis lines and evaluated the functions of VaSTS19 in various pathogen stresses, including powdery mildew, B. cinerea and Pseudomonas syringae pv. tomato DC3000 ( Pst DC3000). VaSTS19 enhanced resistance to powdery mildew and B. cinerea , but increased susceptibility to Pst DC3000. Aniline blue staining revealed that VaSTS19 transgenic lines accumulated more callose compared to nontransgenic control plants, and showed smaller stomatal apertures when exposed to pathogen-associated molecular patterns (flagellin fragment (flg22) or lipopolysaccharides (LPS)). Analysis of the expression of several disease-related genes suggested that VaSTS19 expression enhanced defense responses though salicylic acid (SA) and/or jasmonic acid (JA) signaling pathways. These findings provide a deeper insight into the function of STS genes in defense against pathogens, and a better understanding of the regulatory cross talk between SA and JA pathways.

Computational study of AuSi{sub n} (n=1-9) nanoalloy clusters invoking DFT based descriptors

Energy Technology Data Exchange (ETDEWEB)

Ranjan, Prabhat; Kumar, Ajay [Department of Mechatronics, Manipal University Jaipur Dehmi Kalan, Jaipur-303007 (India); Chakraborty, Tanmoy, E-mail: tanmoy.chakraborty@jaipur.manipal.edu, E-mail: tanmoychem@gmail.com [Department of Chemistry, Manipal University Jaipur Dehmi Kalan, Jaipur-303007 (India)

2016-04-13

Nanoalloy clusters formed between Au and Si are topics of great interest today from both scientific and technological point of view. Due to its remarkable catalytic, electronic, mechanical and magnetic properties Au-Si nanoalloy clusters have extensive applications in the field of microelectronics, catalysis, biomedicine, and jewelry industry. Density Functional Theory (DFT) is a new paradigm of quantum mechanics, which is very much popular to study the electronic properties of materials. Conceptual DFT based descriptors have been invoked to correlate the experimental properties of nanoalloy clusters. In this venture, we have systematically investigated AuSi{sub n} (n=1-9) nanoalloy clusters in the theoretical frame of the B3LYP exchange correlation. The experimental properties of AuSi{sub n} (n=1-9) nanoalloy clusters are correlated in terms of DFT based descriptors viz. HOMO-LUMO gap, Electronegativity (χ), Global Hardness (η), Global Softness (S) and Electrophilicity Index (ω). The calculated HOMO-LUMO gap exhibits interesting odd-even alteration behaviour, indicating that even numbered clusters possess higher stability as compare to their neighbour odd numbered clusters. This study also reflects a very well agreement between experimental bond length and computed data.

Molecular dynamics computer simulation study of Pd{sub n} (n=13, 19, 38 and 55) clusters

Energy Technology Data Exchange (ETDEWEB)

Karabacak, M [Afyon Kocatepe University, Department of Physics, Afyon (Turkey); Oezcelik, S [Gazi University, Department of Physics, Ankara (Turkey); Guevenc, Z B [Cankaya University, Department of Electronics and Communication Engineering, Ankara (Turkey)

2002-07-01

Using constant-energy molecular dynamics and thermal quenching simulations, we have studied minimum-energy structures and energetics, Pd{sub n} (n=13, 19, 38, and 55) clusters employing the Voter and Chen's version of parameterisation of the embedded-atom potential surface. Isomer statistics for Pdn ( n = 13 and 19 ) is obtained from 10000 initial independent configurations, which have been generated along high-energy trajectories (chosen energy values are high enough to melt the clusters). The thermal quenching technique is employed to remove the internal kinetic energy of the clusters. The locally stable isomers are separated from metastable ones. Probabilities belonging to sampling the basins of attractions of each isomers are computed, and then, isomers' energy spectra are analyzed.

Expression of the Grape VaSTS19 Gene in Arabidopsis Improves Resistance to Powdery Mildew and Botrytis cinerea but Increases Susceptibility to Pseudomonas syringe pv Tomato DC3000

Directory of Open Access Journals (Sweden)

Yaqiong Wang

2017-09-01

Full Text Available Stilbene synthase (STS is a key enzyme that catalyzes the biosynthesis of resveratrol compounds and plays an important role in disease resistance. The molecular pathways linking STS with pathogen responses and their regulation are not known. We isolated an STS gene, VaSTS19, from a Chinese wild grape, Vitis amurensis Rupr. cv. “Tonghua-3”, and transferred this gene to Arabidopsis. We then generated VaSTS19-expressing Arabidopsis lines and evaluated the functions of VaSTS19 in various pathogen stresses, including powdery mildew, B. cinerea and Pseudomonas syringae pv. tomato DC3000 (PstDC3000. VaSTS19 enhanced resistance to powdery mildew and B. cinerea, but increased susceptibility to PstDC3000. Aniline blue staining revealed that VaSTS19 transgenic lines accumulated more callose compared to nontransgenic control plants, and showed smaller stomatal apertures when exposed to pathogen-associated molecular patterns (flagellin fragment (flg22 or lipopolysaccharides (LPS. Analysis of the expression of several disease-related genes suggested that VaSTS19 expression enhanced defense responses though salicylic acid (SA and/or jasmonic acid (JA signaling pathways. These findings provide a deeper insight into the function of STS genes in defense against pathogens, and a better understanding of the regulatory cross talk between SA and JA pathways.

2013 EFRC PI Meeting -- Science for Our Nation's Energy Future: Energy Frontier Research Centers Principal Investigators' Meeting, Washington, D.C., July 18-19, 2013

Energy Technology Data Exchange (ETDEWEB)

None, None

2013-07-01

2013 EFRC Principal Investigators’ Meeting, July 18-19, 2013 in Washington D.C. By invitation only--about 500 attendees from the EFRCs and DOE, 235 senior EFRC members and 165 EFRC early career scientists from more than 80 institutions in 31 states, 2 foreign countries and Washington D.C. Over 115 talks and 225 posters

Impact of Air Oxidation on Dissolved Organic Matter from Boom Clay: Comparison Between Natural and Artificial Oxidation Series and In Situ Piezometers Water From Hades Galleries

International Nuclear Information System (INIS)

Blanchart, Pascale; Faure, Pierre; Michels, Raymond; Bruggeman, Christophe; De Craen, Mieke; Parant, Stephane

2012-01-01

Document available in extended abstract form only. The Boom Clay is considered by the Belgian radioactive waste management agency Ondraf/Niras as a possible host rock for the geological disposal of high-level and long-lived radioactive waste. The drilling of galleries and corings in the Boom Clay (Mol, Belgium) leads to perturbations of the initial physical and chemical conditions. In piezometers, the DOC may show considerable and irregular variations through time, with values ranging from 80 to 425 mg/L. The origin and bio-physico-chemical controls of such variations are yet unknown but oxidation and biodegradation were considered as most likely. Three categories of samples were collected with the aim of determining and quantifying different molecular markers representative for the oxidation process: - Fresh as well as air-oxidized Boom Clay samples were collected in the Underground Research Facility HADES of EURIDICE (Mol, Belgium): they represent a natural series of oxidation; - A fresh Boom Clay sample was submitted to laboratory air oxidation (artificial series). In these experiments, powdered clay was heated at 80 deg. C under air flow during 1, 3, 6, 9, 12, 18 months; - Four water samples were collected during January 2010 from different horizons in the Boom Clay by means of piezometers located in the Underground Research Facility. The DOM (dissolved organic matter) of Boom Clay samples (artificial and natural series) was isolated by Soxhlet using pure water as well as by leaching experiments. The quantitative analysis shows an increasing in DOC (Dissolved Organic Carbon) content with oxidation. Qualitative characterizations including spectroscopic (3D-fluorescence) as well as molecular analyses (flash pyrolysis - gas chromatography - mass spectrometry (PyGC-MS) and size exclusion chromatography (SEC-HPLC)) show an evolution of the DOM chemistry with oxidation: - An enrichment in oxygen bearing molecules (acidic poly functional groups); - A decrease in

75 FR 68686 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-9-14, DC-9-15, and DC-9-15F...

Science.gov (United States)

2010-11-09

... Jersey Avenue, SE., Washington, DC 20590. FOR FURTHER INFORMATION CONTACT: Wahib Mina, Aerospace Engineer... requested using the procedures found in 14 CFR 39.19. Send information to ATTN: Wahib Mina, Aerospace...

Stability analysis and structural rules of titanium dioxide clusters (TiO2)n with n = 1-9

International Nuclear Information System (INIS)

Zhang Weiwei; Han Ye; Yao Shuyu; Sun Haiqing

2011-01-01

Highlights: · We investigated the structure and stability of (TiO 2 ) n clusters with n = 1-9. · Some initial structures are introduced and proved to be the real global minimum. · We summarized the structural rules for small (TiO 2 ) n clusters. · The bonding features for the energy increment or decrement of the clusters are investigated. · A general shift of stability and reactivity with size for (TiO 2 ) n clusters. - Abstract: Atomic clusters have been considered as models for fundamental mechanistic insight into complex surfaces and catalysts. The structure and stability of (TiO 2 ) n clusters with n = 1-9 are investigated using the b3lyp hybrid density functional method in this paper. Some of the clusters are proposed initially and proved to be the real global minima. The stability and band gap of the clusters as a function of size are also investigated. The structural rules of the clusters are first summarized. The lowest-lying (TiO 2 ) n isomers tend to form some compact rather than quasi-linear or circular structures. The oxygen atom in 4-fold coordination and the titanium atom in 4-fold coordination favor the cluster stability. The 5-fold coordinated Ti-atom, the Ti-Ti bond and the terminal Ti-O bond lead to stability penalty for the clusters. No evidence for a regular variation in stability or reactivity with size of the clusters has shown. The structural rules can serve as guiding factors for formation research and structure design of (TiO 2 ) n and other transition metal oxide clusters.

Studi Komparasi Fungsi Keanggotaan Fuzzy sebagai Kontroler Bidirectional DC-DC Converter pada Sistem Penyimpan Energi

Directory of Open Access Journals (Sweden)

Eka Prasetyono

2015-09-01

Full Text Available Bidirectional DC-DC converter is needed in the energy storage system. The converter topology used in this paper was a non-isolated bidirectional DC-DC buck-boost converter. This converter worked in two ways, which the charging mode stored energy into battery when load current was less than nominal main DC current (set point and discharging mode transferred energy from battery to the load when its current exceeded set point value. Both of these modes worked automatically according to the load current. The charging and discharging currents were controlled by fuzzy logic controller which was implemented on microcontroller ARM Cortex-M4F STM32F407VG. This paper compares two types of fuzzy membership function (triangular and sigmoid in controlling bidirectional DC-DC converter. The results showed that fuzzy logic controller with triangle membership function and sigmoid as control bidirectional DC-DC converter had no significant different response, both had an average error for charging and discharging process under 4% with ripple current on the main DC bus around 0.5%. The computing time of program for fuzzy logic controller with triangular membership functions had 19.01% faster than sigmoid, and fuzzy logic computation time on a microcontroller with hardware floating point was 60% faster than software floating point.

First-principles study on stability, and growth strategies of small AlnZr (n=1-9) clusters

Science.gov (United States)

Li, Zhi; Zhou, Zhonghao; Wang, Hongbin; Li, Shengli; Zhao, Zhen

2016-09-01

The geometries, relative stability as well as growth strategies of the AlnZr (n=1-9) clusters are investigated with spin polarized density functional theory: BLYP. The results reveal that the AlnZr clusters are more likely to form the dense accumulation structures than the AlN (N=1-10) clusters. The average binding energies of AlnZr are higher than those of AlN clusters. The AlnZr (n=3, 5, and 7) clusters are more stable than others by the differences of the total binding energies. Mülliken population analysis for the AlnZr clusters shows that the electron's adsorption ability of Zr is slightly lower than that of Al except for AlZr cluster. Local peaks of the HOMO-LUMO gap curve are found at n=3, 5, and 7. The reaction energies of AlnZr are higher, which means that AlnZr clusters are easier to react with Al clusters. Zr atom preferential reacts with Al2 cluster. Local peaks of the magnetic dipole moments are found at n=2, 5, and 8.

DC electric springs with DC/DC converters

DEFF Research Database (Denmark)

Wang, Qingsong; Cheng, Ming; Jiang, Yunlei

2016-01-01

The concept of DC electric spring (DCES) was recently proposed to solve the stability issue caused by integrating intermittent renewable energy sources (RESs) to DC microgrids. In this paper, a new topology of DCES is proposed based on DC/DC converters. The proposed DCES consists of a bi-directio......The concept of DC electric spring (DCES) was recently proposed to solve the stability issue caused by integrating intermittent renewable energy sources (RESs) to DC microgrids. In this paper, a new topology of DCES is proposed based on DC/DC converters. The proposed DCES consists of a bi...... and/or constant discharging for batteries is adopted and four operating modes are analyzed as charging-positive, charging-negative, discharging-positive and discharging-negative modes. An additional mechanism for fast charging or fast discharging is also designed to secure normal operation...... of batteries. With the proposed DCES, the power fluctuations due to intermittent RESs can be passed to non-critical loads (NCLs) and batteries while power on critical loads (CLs) is kept stable. This is possibly the first attempt to design a DCES with only DC/DC converters. The performances of the proposed...

Advanced DC/DC converters

CERN Document Server

Luo, Fang Lin

2003-01-01

DC/DC conversion techniques have undergone rapid development in recent decades. With the pioneering work of these authors, DC/DC converters have now moved into their sixth generation. This book offers a concise, practical presentation of DC/DC converters, summarizing the spectrum of conversion tecnologies and presentingmany new ideas and more than 100 new topologies. Nowhere else in the literature are DC/DC converters so logically sorted and systematically introduced, and nowhere else can readers find detailed information on prototype topologies that represent a major contribution to modern power engineering. More than 320 figures, 60 tables, and 500 formulae facilitate understand and provide precise data.

A Unidirectional DC-DC Autotransformer for DC Grid Application

Directory of Open Access Journals (Sweden)

Meng Zhou

2018-03-01

Full Text Available Conventional unidirectional DC-DC converters for DC grid application employ DC-AC-DC two-stage conversion technology and suffer from high converter cost and power loss. To solve these issues, a unidirectional step-up DC-DC autotransformer (UUDAT and a unidirectional step-down DC-DC autotransformer (DUDAT are studied. The UUDAT and DUDAT are composed of a series connection of diode bridges and voltage source converters. Topologies of UUDAT and DUDAT are detailed. The harmonic and un-controllability issues are discussed. Control and possible application scenarios for UUDAT and DUDAT are depicted. DC fault isolation mechanism and the methods of dimensioning the voltage and power ratings of the components in UUDAT and DUDAT are studied. Extensive simulations on power system level and experiments on a UUDAT and DUDAT prototype verified their technical feasibility.

A resonant dc-dc power converter assembly

DEFF Research Database (Denmark)

2015-01-01

The present invention relates to a resonant DC-DC power converter assembly comprising a first resonant DC-DC power converter and a second resonant DC-DC power converter having identical circuit topologies. A first inductor of the first resonant DC-DC power converter and a second inductor of the s......The present invention relates to a resonant DC-DC power converter assembly comprising a first resonant DC-DC power converter and a second resonant DC-DC power converter having identical circuit topologies. A first inductor of the first resonant DC-DC power converter and a second inductor...... of the second resonant DC-DC power converter are configured for magnetically coupling the first and second resonant DC-DC power converters to each other to forcing substantially 180 degrees phase shift, or forcing substantially 0 degree phase shift, between corresponding resonant voltage waveforms of the first...

Step-Up DC-DC converters

DEFF Research Database (Denmark)

Forouzesh, Mojtaba; Siwakoti, Yam P.; Gorji, Saman A.

2017-01-01

on the general law and framework of the development of next-generation step-up dc-dc converters, this paper aims to comprehensively review and classify various step-up dc-dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage......DC-DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which......-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc-dc converters are presented and summarized with comparative study of different voltage-boosting techniques....

A resonant dc-dc power converter assembly

OpenAIRE

Madsen, Mickey Pierre

2015-01-01

The present invention relates to a resonant DC-DC power converter assembly comprising a first resonant DC-DC power converter and a second resonant DC-DC power converter having identical circuit topologies. A first inductor of the first resonant DC-DC power converter and a second inductor of the second resonant DC-DC power converter are configured for magnetically coupling the first and second resonant DC-DC power converters to each other to forcing substantially 180 degrees phase shift, or fo...

Far-infrared spectra of yttrium-doped gold clusters Au(n)Y (n=1-9).

Science.gov (United States)

Lin, Ling; Claes, Pieterjan; Gruene, Philipp; Meijer, Gerard; Fielicke, André; Nguyen, Minh Tho; Lievens, Peter

2010-06-21

The geometric, spectroscopic, and electronic properties of neutral yttrium-doped gold clusters Au(n)Y (n=1-9) are studied by far-infrared multiple photon dissociation (FIR-MPD) spectroscopy and quantum chemical calculations. Comparison of the observed and calculated vibrational spectra allows the structures of the isomers present in the molecular beam to be determined. Most of the isomers for which the IR spectra agree best with experiment are calculated to be the energetically most stable ones. Attachment of xenon to the Au(n)Y cluster can cause changes in the IR spectra, which involve band shifts and band splittings. In some cases symmetry changes, as a result of the attachment of xenon atoms, were also observed. All the Au(n)Y clusters considered prefer a low spin state. In contrast to pure gold clusters, which exhibit exclusively planar lowest-energy structures for small sizes, several of the studied species are three-dimensional. This is particularly the case for Au(4)Y and Au(9)Y, while for some other sizes (n=5, 8) the 3D structures have an energy similar to that of their 2D counterparts. Several of the lowest-energy structures are quasi-2D, that is, slightly distorted from planar shapes. For all the studied species the Y atom prefers high coordination, which is different from other metal dopants in gold clusters.

Cluster Correlation in Mixed Models

Science.gov (United States)

Gardini, A.; Bonometto, S. A.; Murante, G.; Yepes, G.

2000-10-01

We evaluate the dependence of the cluster correlation length, rc, on the mean intercluster separation, Dc, for three models with critical matter density, vanishing vacuum energy (Λ=0), and COBE normalization: a tilted cold dark matter (tCDM) model (n=0.8) and two blue mixed models with two light massive neutrinos, yielding Ωh=0.26 and 0.14 (MDM1 and MDM2, respectively). All models approach the observational value of σ8 (and hence the observed cluster abundance) and are consistent with the observed abundance of damped Lyα systems. Mixed models have a motivation in recent results of neutrino physics; they also agree with the observed value of the ratio σ8/σ25, yielding the spectral slope parameter Γ, and nicely fit Las Campanas Redshift Survey (LCRS) reconstructed spectra. We use parallel AP3M simulations, performed in a wide box (of side 360 h-1 Mpc) and with high mass and distance resolution, enabling us to build artificial samples of clusters, whose total number and mass range allow us to cover the same Dc interval inspected through Automatic Plate Measuring Facility (APM) and Abell cluster clustering data. We find that the tCDM model performs substantially better than n=1 critical density CDM models. Our main finding, however, is that mixed models provide a surprisingly good fit to cluster clustering data.

Step-Up DC-DC converters

DEFF Research Database (Denmark)

Forouzesh, Mojtaba; Siwakoti, Yam P.; Gorji, Saman A.

2017-01-01

on the general law and framework of the development of next-generation step-up dc-dc converters, this paper aims to comprehensively review and classify various step-up dc-dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage...

Transition towards DC micro grids: From an AC to a hybrid AC and DC energy infrastructure

Directory of Open Access Journals (Sweden)

Evi Ploumpidou

2017-12-01

Full Text Available Our electricity is predominantly powered by alternating current (AC, ever since the War of Currents ended in the favor of Nicola Tesla at the end of the 19th century. However, lots of the appliances we use, such as electronics and lights with light-emitting diode (LED technology, work internally on direct current (DC and it is projected that the number of these appliances will increase in the near future. Another contributor to the increase in DC consumption is the ongoing electrification of mobility (Electric Vehicles (EVs. At the same time, photovoltaics (PV generate DC voltages, while the most common storage technologies also use DC. In order to integrate all these appliances and technologies to the existing AC grid, there is a need for converters which introduce power losses. By distributing DC power to DC devices instead of converting it to AC first, it is possible to avoid substantial energy losses that occur every time electricity is converted. This situation initiated the concept for the implementation of the DC-Flexhouse project. A prototype DC installation will be developed and tested in one of the buildings of the developing living lab area called the District of Tomorrow (De Wijk van Morgen which is located in Heerlen, the Netherlands. A neighborhood cooperative (Vrieheide cooperatie is also part of the consortium in order to address the aspect of social acceptance. Although DC seems to be a promising solution for a more sustainable energy system, the business case is still debatable due to both technology- and market-related challenges. The current energy infrastructure is predominantly based on AC, manufacturers produce devices based on AC standards and people are using many AC products across a long life span. This Smart Energy Buildings & Cities (SEB&C PDEng project is a contribution to the DC-Flexhouse project. The aim is to analyze the challenges in the transition to DC micro grids, assess the market potential of DC

Absence of the BRAF mutation in HBME1+ and CK19+ atypical cell clusters in Hashimoto thyroiditis: supportive evidence against preneoplastic change.

Science.gov (United States)

Nasr, Michel R; Mukhopadhyay, Sanjay; Zhang, Shengle; Katzenstein, Anna-Luise A

2009-12-01

An association between Hashimoto thyroiditis and papillary thyroid carcinoma has been postulated for decades. We undertook this study to identify potential precursors of papillary thyroid carcinoma in Hashimoto thyroiditis using a combination of morphologic, immunohistochemical, and molecular techniques. For the study, samples from 59 cases of Hashimoto thyroiditis were stained with antibodies to HBME1 and cytokeratin (CK)19. Tiny HBME1+ and CK19+ atypical cell clusters were identified and analyzed for the BRAF mutation by the colorimetric Mutector assay and allele-specific polymerase chain reaction. HBME1+ and CK19+ atypical cell clusters were identified in 12 (20%) of 59 cases. The minute size (Hashimoto thyroiditis.

Analysis and distributed control of power flow in DC microgrids to improve system efficiency

DEFF Research Database (Denmark)

Chen, Fang; Burgos, Rolando; Boroyevich, Dushan

2016-01-01

DC Microgrid attains popularity in integrating renewable energy sources and batteries. It also has the potential to achieve higher efficiency than ac power grid under the condition of optimized power flow. In this paper, a general dc microgrid is modeled based on a cluster of general dc nodes......, which includes constant power renewables generation, droop-controlled voltage source and different kinds of load. Then the dc power flow is solved for optimization. A voltage restoration method based on consensus communication is used to restore the voltage deviation from droop characteristic...

Patterns of variation at Ustilago maydis virulence clusters 2A and 19A largely reflect the demographic history of its populations.

Directory of Open Access Journals (Sweden)

Ronny Kellner

Full Text Available The maintenance of an intimate interaction between plant-biotrophic fungi and their hosts over evolutionary times involves strong selection and adaptative evolution of virulence-related genes. The highly specialised maize pathogen Ustilago maydis is assigned with a high evolutionary capability to overcome host resistances due to its high rates of sexual recombination, large population sizes and long distance dispersal. Unlike most studied fungus-plant interactions, the U. maydis - Zea mays pathosystem lacks a typical gene-for-gene interaction. It exerts a large set of secreted fungal virulence factors that are mostly organised in gene clusters. Their contribution to virulence has been experimentally demonstrated but their genetic diversity within U. maydis remains poorly understood. Here, we report on the intraspecific diversity of 34 potential virulence factor genes of U. maydis. We analysed their sequence polymorphisms in 17 isolates of U. maydis from Europe, North and Latin America. We focused on gene cluster 2A, associated with virulence attenuation, cluster 19A that is crucial for virulence, and the cluster-independent effector gene pep1. Although higher compared to four house-keeping genes, the overall levels of intraspecific genetic variation of virulence clusters 2A and 19A, and pep1 are remarkably low and commensurate to the levels of 14 studied non-virulence genes. In addition, each gene is present in all studied isolates and synteny in cluster 2A is conserved. Furthermore, 7 out of 34 virulence genes contain either no polymorphisms or only synonymous substitutions among all isolates. However, genetic variation of clusters 2A and 19A each resolve the large scale population structure of U. maydis indicating subpopulations with decreased gene flow. Hence, the genetic diversity of these virulence-related genes largely reflect the demographic history of U. maydis populations.

75 FR 23571 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-15, DC...

Science.gov (United States)

2010-05-04

... Airworthiness Directives; McDonnell Douglas Corporation Model DC- 10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10... amends Sec. 39.13 by adding the following new AD: 2010-09-12 McDonnell Douglas Corporation: Amendment 39... to McDonnell Douglas Corporation Model DC- 10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A...

DC Home Appliances for DC Distribution System

Directory of Open Access Journals (Sweden)

MUHAMMAD KAMRAN

2017-10-01

Full Text Available This paper strengthens the idea of DC distribution system for DC microgrid consisting of a building of 50 apartments. Since the war of currents AC system has been dominant because of the paucity of research in the protection of the DC system. Now with the advance research in power electronics material and components, generation of electricity is inherently DC as by solar PV, fuel cell and thermoelectric generator that eliminates the rectification process. Transformers are replaced by the power electronics buck-boost converters. DC circuit breakers have solved the protection problems for both DC transmission and distribution system. In this paper 308V DC microgrid is proposed and home appliances (DC internal are modified to operate on 48V DC from DC distribution line. Instead of using universal and induction motors in rotary appliances, BLDC (Brushless DC motors are proposed that are highly efficient with minimum electro-mechanical and no commutation losses. Proposed DC system reduces the power conversion stages, hence diminishes the associated power losses and standby losses that boost the overall system efficiency. So in view of all this a conventional AC system can be replaced by a DC system that has many advantages by cost as well as by performance

A Cluster Analytic Examination of Acculturation and Health Status among Asian Americans in the Washington DC Metropolitan Area, United States

Science.gov (United States)

Lee, Sunmin; Chen, Lu; He, Xin; Miller, Matthew J.; Juon, Hee-Soon

2013-01-01

Previous studies reported mixed findings on the relationship between acculturation and health status among Asian Americans due to different types of acculturation measures used or different Asian subgroups involved in various studies. We aim to fill the gap by applying multiple measures of acculturation in a diverse sample of Asian subgroups. A cross sectional study was conducted among Chinese, Korean and Vietnamese Americans in Washington D.C. Metropolitan Area to examine the association between health status and acculturation using multiple measures including the Suinn-Lew Asian Self-Identity Acculturation (SL-ASIA) scale, clusters based on responses to SL-ASIA, language preference, length of stay, age at arrival in the United Sates and self-identity. Three clusters (Asian (31%); Bicultural (47%); and American (22%)) were created by using a two-step hierarchical method and Bayesian Information Criterion values. Across all the measures, more acculturated individuals were significantly more likely to report good health than those who were less acculturated after adjusting for covariates. Specifically, those in the American cluster were 3.8 times (95% Confidence Interval (CI): 2.2, 6.6) more likely and those in the Bicultural cluster were 1.7 times more likely (95% CI: 1.1, 2.4) to report good health as compared to those in the Asian cluster. When the conventional standardized SL-ASIA summary score (range: −1.4 to 1.4) was used, a one point increase was associated with 2.2 times greater odds of reporting good health (95% CI: 1.5, 3.2). However, the interpretation may be challenging due to uncertainty surrounding the meaning of a one point increase in SL-ASIA summary score. Among all the measures used, acculturation clusters better approximated the acculturation process and provided us with a more accurate test of the association in the population. Variables included in this measure were more relevant for our study sample and may have worked together to capture the

A CMOS RF-to-DC Power Converter With 86% Efficiency and -19.2-dBm Sensitivity

KAUST Repository

Almansouri, Abdullah Saud Mohammed; Ouda, Mahmoud H.; Salama, Khaled N.

2018-01-01

This paper proposes an RF-to-dc power converter for ambient wireless powering that is efficient, highly sensitive, and less dependent on the load resistance with an extended dynamic range. The proposed rectifier utilizes a variable biasing technique to control the conduction of the rectifying transistors selectively, hence minimizing the leakage current; unlike the prior work that has a fixed feedback resistors, which limits the efficient operation to a relatively high RF power and causes a drop in the peak power conversion efficiency (PCE). The proposed design is fabricated using a 0.18-μm standard CMOS technology and occupies an area of 8800 μm². The measurement results show an 86% PCE and -19.2-dBm (12 μW) sensitivity when operating at the medical band 433 MHz with a 100-kΩ load. Furthermore, the PCE is 66%, and the sensitivity is -18.2 dBm (15.1 μW) when operating at UHF 900 MHz with a 100-kΩ load.

A CMOS RF-to-DC Power Converter With 86% Efficiency and -19.2-dBm Sensitivity

KAUST Repository

Almansouri, Abdullah Saud Mohammed

2018-01-09

This paper proposes an RF-to-dc power converter for ambient wireless powering that is efficient, highly sensitive, and less dependent on the load resistance with an extended dynamic range. The proposed rectifier utilizes a variable biasing technique to control the conduction of the rectifying transistors selectively, hence minimizing the leakage current; unlike the prior work that has a fixed feedback resistors, which limits the efficient operation to a relatively high RF power and causes a drop in the peak power conversion efficiency (PCE). The proposed design is fabricated using a 0.18-μm standard CMOS technology and occupies an area of 8800 μm². The measurement results show an 86% PCE and -19.2-dBm (12 μW) sensitivity when operating at the medical band 433 MHz with a 100-kΩ load. Furthermore, the PCE is 66%, and the sensitivity is -18.2 dBm (15.1 μW) when operating at UHF 900 MHz with a 100-kΩ load.

Family of multiport bidirectional DC-DC converters

NARCIS (Netherlands)

Tao, H.; Kotsopoulos, A.; Duarte, J.L.; Hendrix, M.A.M.

2006-01-01

Multiport DC-DC converters are of potential interest in applications such as generation systems utilising multiple sustainable energy sources. A family of multiport bidirectional DC-DC converters derived from a general topology is presented. The topology shows a combination of DC-link and magnetic

EST Table: DC543015 [KAIKOcDNA[Archive

Lifescience Database Archive (English)

Full Text Available DC543015 E_FL_dpe-_19C07_F_0 10/09/28 32 %/171 aa ref|XP_002572677.1| nuclear movement... protein related [Schistosoma mansoni] emb|CAZ28909.1| nuclear movement protein related [Schistosoma mans

Design and Testing of Boost Type DC/DC Converter for DC Motor Control Applications

OpenAIRE

Samman, Faizal Arya; Akil, Yusri Syam; Noor, Nirwan A.

2017-01-01

in The Proceeding of The 2nd International Symposium on Smart Material and Mechatronics 2015 This paper presents the design and testing of a boost type DC/DC converter circuit, which can be used for DC motor control applications. The Boost converter is designed using DC chopper and DC chopper cascade configurations. The experimental setup was made by connecting the boost converter circuit with four types of DC motor, i.e. self-excited DC motor shunt, series, compound and separately exci...

Conjunction of radial basis function interpolator and artificial intelligence models for time-space modeling of contaminant transport in porous media

Science.gov (United States)

Nourani, Vahid; Mousavi, Shahram; Dabrowska, Dominika; Sadikoglu, Fahreddin

2017-05-01

As an innovation, both black box and physical-based models were incorporated into simulating groundwater flow and contaminant transport. Time series of groundwater level (GL) and chloride concentration (CC) observed at different piezometers of study plain were firstly de-noised by the wavelet-based de-noising approach. The effect of de-noised data on the performance of artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) was evaluated. Wavelet transform coherence was employed for spatial clustering of piezometers. Then for each cluster, ANN and ANFIS models were trained to predict GL and CC values. Finally, considering the predicted water heads of piezometers as interior conditions, the radial basis function as a meshless method which solves partial differential equations of GFCT, was used to estimate GL and CC values at any point within the plain where there is not any piezometer. Results indicated that efficiency of ANFIS based spatiotemporal model was more than ANN based model up to 13%.

Five-Level Active-Neutral-Point-Clamped DC/DC Converter for Medium-Voltage DC Grids

DEFF Research Database (Denmark)

Liu, Dong; Deng, Fujin; Chen, Zhe

2017-01-01

This paper proposes a five-level active-neutralpoint- clamped (5L-ANPC) dc/dc converter for applications in medium voltage dc (MVDC) grids. A modulation strategy is proposed for the 5L-ANPC dc/dc converter to generate multilevel voltage waveforms, which can effectively reduce voltage change rate dv...... effectively eliminate high voltage leaps caused by the dead time effect. In addition, a capacitor voltage control strategy is proposed for the 5L-ANPC dc/dc converter to ensure the balanced flying capacitor voltage and desired five-level voltage waveforms. Finally, simulation and experimental studies...

Control of improved full-bridge three-level DC/DC converter for wind turbines in a DC grid

DEFF Research Database (Denmark)

Deng, Fujin; Chen, Zhe

2013-01-01

transformer in the IFBTL dc/dc converter. A modulation strategy, including two operation modes, is proposed for the IFBTL dc/dc converter. Then, a voltage balancing control strategy is proposed for the IFBTL dc/dc converter. Furthermore, the control of the wind turbine based on the IFBTL dc/dc converter......This paper presents an improved full-bridge three-level (IFBTL) dc/dc converter for a wind turbine in a dc grid by inserting a passive filter into the dc/dc converter to improve the performance of the converter. The passive filter can effectively reduce the voltage stress of the medium frequency...

DC8 and DC13 var genes associated with severe malaria bind avidly to diverse endothelial cells.

Directory of Open Access Journals (Sweden)

Marion Avril

Full Text Available During blood stage infection, Plasmodium falciparum infected erythrocytes (IE bind to host blood vessels. This virulence determinant enables parasites to evade spleen-dependent killing mechanisms, but paradoxically in some cases may reduce parasite fitness by killing the host. Adhesion of infected erythrocytes is mediated by P. falciparum erythrocyte membrane protein 1 (PfEMP1, a family of polymorphic adhesion proteins encoded by var genes. Whereas cerebral binding and severe malaria are associated with parasites expressing DC8 and DC13 var genes, relatively little is known about the non-brain endothelial selection on severe malaria adhesive types. In this study, we selected P. falciparum-IEs on diverse endothelial cell types and demonstrate that DC8 and DC13 var genes were consistently among the major var transcripts selected on non-brain endothelial cells (lung, heart, bone marrow. To investigate the molecular basis for this avid endothelial binding activity, recombinant proteins were expressed from the predominant upregulated DC8 transcript, IT4var19. In-depth binding comparisons revealed that multiple extracellular domains from this protein bound brain and non-brain endothelial cells, and individual domains largely did not discriminate between different endothelial cell types. Additionally, we found that recombinant DC8 and DC13 CIDR1 domains exhibited a widespread endothelial binding activity and could compete for DC8-IE binding to brain endothelial cells, suggesting they may bind the same host receptor. Our findings provide new insights into the interaction of severe malaria adhesive types and host blood vessels and support the hypothesis that parasites causing severe malaria express PfEMP1 variants with a superior ability to adhere to diverse endothelial cell types, and may therefore endow these parasites with a growth and transmission advantage.

IGBT Based DC/DC Converter

Directory of Open Access Journals (Sweden)

M. Akherraz

1997-12-01

Full Text Available This paper presents an in-depth analytical and experimental investigation of an indirect DC-DC converter. The DC-AC conversion is a full bridge based on IGBT power modules, and the AC-DC conversion is done via a high  frequency AC link and a first diode bridge. The AC link, which consists of snubbing capacitors and a variable air-gap transformer, is analytically designed to fulfill Zero Voltage commutation requirement. The proposed converter is simulated using PSPICE and a prototype is designed built and tested in the laboratory. PSPICE simulation and experimental results are presented and compared.

Three-port DC-DC converter with new integrated transformer for DC Distribution Systems

DEFF Research Database (Denmark)

Ouyang, Ziwei; Andersen, Michael A. E.

2014-01-01

A new integrated transformer for three-port dc-dc converter is proposed to overcome the power coupling effect existed in some known multiple inputs dc-dc converters. Orthogonal primary windings arrangement and in series connection of diagonal secondary Windings enables a fully power decoupling...

Three new DC-to-DC Single-Switch Converters

Directory of Open Access Journals (Sweden)

Barry W. Williams

2017-06-01

Full Text Available This paper presents a new family of three previously unidentified dc-to-dc converters, buck, boost, and buck-boost voltage-transfer-function topologies, which offer advantageous transformer coupling features and low capacitor dc voltage stressing. The three single-switch, single-diode, converters offer the same features as basic dc-to-dc converters, such as the buck function with continuous output current and the boost function with continuous input current. Converter time-domain simulations and experimental results (including transformer coupling support and extol the dc-to-dc converter concepts and analysis presented.

Validity of the classical monte carlo method to model the magnetic properties of a large transition-metal cluster: Mn19.

Science.gov (United States)

Lima, Nicola; Caneschi, Andrea; Gatteschi, Dante; Kritikos, Mikael; Westin, L Gunnar

2006-03-20

The susceptibility of the large transition-metal cluster [Mn19O12(MOE)14(MOEH)10].MOEH (MOE = OC2H2O-CH3) has been fitted through classical Monte Carlo simulation, and an estimation of the exchange coupling constants has been done. With these results, it has been possible to perform a full-matrix diagonalization of the cluster core, which was used to provide information on the nature of the low-lying levels.

K19 capsular polysaccharide of Acinetobacter baumannii is produced via a Wzy polymerase encoded in a small genomic island rather than the KL19 capsule gene cluster.

Science.gov (United States)

Kenyon, Johanna J; Shneider, Mikhail M; Senchenkova, Sofya N; Shashkov, Alexander S; Siniagina, Maria N; Malanin, Sergey Y; Popova, Anastasiya V; Miroshnikov, Konstantin A; Hall, Ruth M; Knirel, Yuriy A

2016-08-01

Polymerization of the oligosaccharides (K units) of complex capsular polysaccharides (CPSs) requires a Wzy polymerase, which is usually encoded in the gene cluster that directs K unit synthesis. Here, a gene cluster at the Acinetobacter K locus (KL) that lacks a wzy gene, KL19, was found in Acinetobacter baumannii ST111 isolates 28 and RBH2 recovered from hospitals in the Russian Federation and Australia, respectively. However, these isolates produced long-chain capsule, and a wzy gene was found in a 6.1 kb genomic island (GI) located adjacent to the cpn60 gene. The GI also includes an acetyltransferase gene, atr25, which is interrupted by an insertion sequence (IS) in RBH2. The capsule structure from both strains was →3)-α-d-GalpNAc-(1→4)-α-d-GalpNAcA-(1→3)-β-d-QuipNAc4NAc-(1→, determined using NMR spectroscopy. Biosynthesis of the K unit was inferred to be initiated with QuiNAc4NAc, and hence the Wzy forms the β-(1→3) linkage between QuipNAc4NAc and GalpNAc. The GalpNAc residue is 6-O-acetylated in isolate 28 only, showing that atr25 is responsible for this acetylation. The same GI with or without an IS in atr25 was found in draft genomes of other KL19 isolates, as well as ones carrying a closely related CPS gene cluster, KL39, which differs from KL19 only in a gene for an acyltransferase in the QuiNAc4NR synthesis pathway. Isolates carrying a KL1 variant with the wzy and atr genes each interrupted by an ISAba125 also have this GI. To our knowledge, this study is the first report of genes involved in capsule biosynthesis normally found at the KL located elsewhere in A. baumannii genomes.

75 FR 60602 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-15, DC...

Science.gov (United States)

2010-10-01

... Airworthiness Directives; McDonnell Douglas Corporation Model DC- 10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10... adding the following new AD: 2010-20-14 McDonnell Douglas Corporation: Amendment 39-16449. Docket No. FAA... the airplanes identified in paragraphs (c)(1) and (c)(2) of this AD. (1) McDonnell Douglas Corporation...

75 FR 38943 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-30, DC...

Science.gov (United States)

2010-07-07

...-0672; Directorate Identifier 2010-NM-047-AD] RIN 2120-AA64 Airworthiness Directives; McDonnell Douglas...: McDonnell Douglas Corporation: Docket No. FAA-2010-0672; Directorate Identifier 2010-NM-047-AD. Comments Due... applies to McDonnell Douglas Corporation Model DC- 10-10, DC-10-10F, DC-10-30, DC-10-30F (KDC-10), DC-10...

75 FR 6160 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-15, DC...

Science.gov (United States)

2010-02-08

...-0032; Directorate Identifier 2009-NM-213-AD] RIN 2120-AA64 Airworthiness Directives; McDonnell Douglas...: McDonnell Douglas Corporation: Docket No. FAA-2010-0032; Directorate Identifier 2009-NM-213-AD. Comments Due... applies to McDonnell Douglas Corporation Model DC- 10-10, DC-10-10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A...

Asteroseismology of the Open Clusters NGC 6791, NGC 6811, and NGC 6819 from 19 Months of Kepler Photometry

DEFF Research Database (Denmark)

Corsaro, Enrico; Stello, Dennis; Huber, Daniel

2012-01-01

We studied solar-like oscillations in 115 red giants in the three open clusters, NGC 6791, NGC 6811, and NGC 6819, based on photometric data covering more than 19 months with NASA's Kepler space telescope. We present the asteroseismic diagrams of the asymptotic parameters δν02, δν01, and ϵ, which...

75 FR 61989 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-8-31, DC-8-32, DC-8-33, DC-8-41...

Science.gov (United States)

2010-10-07

... Airworthiness Directives; McDonnell Douglas Corporation Model DC- 8-31, DC-8-32, DC-8-33, DC-8-41, DC-8-42, and... to all of the McDonnell Douglas Corporation airplanes identified above. The existing AD currently... the following new airworthiness directive (AD): 2010-21-03 McDonnell Douglas Corporation: Amendment 39...

Multi Bus DC-DC Converter in Electric Hybrid Vehicles

Science.gov (United States)

Krithika, V.; Subramaniam, C.; Sridharan, R.; Geetha, A.

2018-04-01

This paper is cotncerned with the design, simulation and fabrication of the prototype of a Multi bus DC- DC converter operating from 42V DC and delivering 14V DC and 260V DC. As a result, three DC buses are interconnected through a single power electronic circuitry. Such a requirement is energized in the development of a hybrid electric automobile which uses the technology of fuel cell. This is implemented by using a Bidirectional DC-DC converter configuration which is ideally suitable for multiple outputs with mutual electrical isolation. For the sake of reduced size and cost of step-up transformer, selection of a high frequency switching cycle at 10 KHz was done.

Step-Up DC-DC Power Converter

DEFF Research Database (Denmark)

2015-01-01

The present invention relates to a step-up DC-DC power converter which comprises a primary side circuit and a secondary side circuit coupled through a galvanic isolation barrier. The primary side circuit comprises a positive and a negative input terminal for receipt of an input voltage and an input...... being charged from the input voltage and discharged to the output capacitor through the galvanic isolation barrier in accordance with a switch control signal to produce the converter output voltage. The step-up DC-DC power converter comprises an electrical short-circuit connection across the galvanic...

AC-DC PFC Converter Using Combination of Flyback Converter and Full-bridge DC-DC Converter

Directory of Open Access Journals (Sweden)

Moh. Zaenal Efendi

2014-06-01

Full Text Available This paper presents a combination of power factor correction converter using Flyback converter and Full-bridge dc-dc converter in series connection. Flyback converter is operated in discontinuous conduction mode so that it can serve as a power factor correction converter and meanwhile Full-bridge dc-dc converter is used for dc regulator. This converter system is designed to produce a 86 Volt of output voltage and 2 A of output current. Both simulation and experiment results show that the power factor of this converter achieves up to 0.99 and meets harmonic standard of IEC61000-3-2. Keywords: Flyback Converter, Full-bridge DC-DC Converter, Power Factor Correction.

Early Oscillation Detection for DC/DC Converter Fault Diagnosis

Science.gov (United States)

Wang, Bright L.

2011-01-01

The electrical power system of a spacecraft plays a very critical role for space mission success. Such a modern power system may contain numerous hybrid DC/DC converters both inside the power system electronics (PSE) units and onboard most of the flight electronics modules. One of the faulty conditions for DC/DC converter that poses serious threats to mission safety is the random occurrence of oscillation related to inherent instability characteristics of the DC/DC converters and design deficiency of the power systems. To ensure the highest reliability of the power system, oscillations in any form shall be promptly detected during part level testing, system integration tests, flight health monitoring, and on-board fault diagnosis. The popular gain/phase margin analysis method is capable of predicting stability levels of DC/DC converters, but it is limited only to verification of designs and to part-level testing on some of the models. This method has to inject noise signals into the control loop circuitry as required, thus, interrupts the DC/DC converter's normal operation and increases risks of degrading and damaging the flight unit. A novel technique to detect oscillations at early stage for flight hybrid DC/DC converters was developed.

Superconducting energy stabilizer with charging and discharging DC-DC converters

International Nuclear Information System (INIS)

Kim, S.H.; Kostecki, E.L.; DeWinkel, C.C.

1992-01-01

This patent describes a superconducting energy stabilizer having multiple load connections and employing DC-DC conversion for storing energy in a superconducting inductive energy storage device having a first end and a second end, and for releasing the stored energy from the superconducting inductive energy storage device to a load or loads or to a utility or an industrial electrical distribution system, the superconducting energy stabilizer having multiple load connections and employing DC-DC conversion. It comprises: energy storage cell means for supplying energy to the load, discharging DC-DC converter means for releasing energy from the superconducting inductive energy storage device to the energy storage cell means, the discharging DC-DC converter means having input terminals, output terminals, and a discharging control line means for carrying signals controlling the operation of the discharging DC-DC converter means, one of the input terminals of the discharging DC-DC converter means coupled to the first end of the superconducting energy storage device

dc Arc Fault Effect on Hybrid ac/dc Microgrid

Science.gov (United States)

Fatima, Zahra

The advent of distributed energy resources (DER) and reliability and stability problems of the conventional grid system has given rise to the wide spread deployment of microgrids. Microgrids provide many advantages by incorporating renewable energy sources and increasing the reliability of the grid by isolating from the main grid in case of an outage. AC microgrids have been installed all over the world, but dc microgrids have been gaining interest due to the advantages they provide over ac microgrids. However the entire power network backbone is still ac and dc microgrids require expensive converters to connect to the ac power network. As a result hybrid ac/dc microgrids are gaining more attention as it combines the advantages of both ac and dc microgrids such as direct integration of ac and dc systems with minimum number of conversions which increases the efficiency by reducing energy losses. Although dc electric systems offer many advantages such as no synchronization and no reactive power, successful implementation of dc systems requires appropriate protection strategies. One unique protection challenge brought by the dc systems is dc arc faults. A dc arc fault is generated when there is a gap in the conductor due to insulation degradation and current is used to bridge the gap, resulting in an arc with very high temperature. Such a fault if it goes undetected and is not extinguished can cause damage to the entire system and cause fires. The purpose of the research is to study the effect of the dc arc fault at different locations in the hybrid ac/dc microgrid and provide insight on the reliability of the grid components when it is impacted by arc faults at various locations in the grid. The impact of dc arc fault at different locations on the performance of the PV array, wind generation, and constant power loads (CPL) interfaced with dc/dc converters is studied. MATLAB/Simulink is used to model the hybrid ac/dc microgrid and arc fault.

Milliwatt dc/dc Inverter

Science.gov (United States)

Mclyman, C. W.

1983-01-01

Compact dc/dc inverter uses single integrated-circuit package containing six inverter gates that generate and amplify 100-kHz square-wave switching signal. Square-wave switching inverts 10-volt local power to isolated voltage at another desired level. Relatively high operating frequency reduces size of filter capacitors required, resulting in small package unit.

75 FR 63040 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-30, DC...

Science.gov (United States)

2010-10-14

... Airworthiness Directives; McDonnell Douglas Corporation Model DC- 10-10, DC-10-10F, DC-10-30, DC-10-30F (KDC-10... following new airworthiness directive (AD): 2010-21-13 McDonnell Douglas Corporation: Amendment 39-16473... November 18, 2010. Affected ADs (b) None. Applicability (c) This AD applies to McDonnell Douglas...

75 FR 68246 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-15, DC...

Science.gov (United States)

2010-11-05

...-1044; Directorate Identifier 2010-NM-033-AD] RIN 2120-AA64 Airworthiness Directives; McDonnell Douglas..., 2007) and adding the following new AD: McDonnell Douglas Corporation: Docket No. FAA-2010-1044.... Applicability (c) This AD applies to all McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, DC-10-15, DC...

Overview of Multi-DC-Bus Solutions for DC Microgrids

DEFF Research Database (Denmark)

Ricchiuto, D.; Mastromauro, R.A.; Liserre, Marco

2013-01-01

DC Microgrids have recently received a lot of attention in the last years due to high penetration of renewable energy sources as well as distributed energy storage systems. In the future DC microgrids could be preferable respect to AC microgrids in terms of redundancy since multi-DC-Bus solutions...... could provide a continuative power supply to the loads. An overview of Multi-DC-Bus solutions is presented in this paper. The performances are compared on the basis of possible DC microgrid configurations, redundancy, different DC voltage levels....

DC to DC power converters and methods of controlling the same

Science.gov (United States)

Steigerwald, Robert Louis; Elasser, Ahmed; Sabate, Juan Antonio; Todorovic, Maja Harfman; Agamy, Mohammed

2012-12-11

A power generation system configured to provide direct current (DC) power to a DC link is described. The system includes a first power generation unit configured to output DC power. The system also includes a first DC to DC converter comprising an input section and an output section. The output section of the first DC to DC converter is coupled in series with the first power generation unit. The first DC to DC converter is configured to process a first portion of the DC power output by the first power generation unit and to provide an unprocessed second portion of the DC power output of the first power generation unit to the output section.

RNA interference of two glutathione S-transferase genes, Diaphorina citri DcGSTe2 and DcGSTd1, increases the susceptibility of Asian citrus psyllid (Hemiptera: Liviidae) to the pesticides fenpropathrin and thiamethoxam.

Science.gov (United States)

Yu, Xiudao; Killiny, Nabil

2018-03-01

The Asian citrus psyllid, Diaphorina citri Kuwayama, is an important agricultural pest of citrus globally. Foliar application of chemical insecticides is the most widely used option for reducing D. citri populations. Knockdown of glutathione S-transferase (GST) in several insect species leads to increased susceptibility to insecticides; however, information about the detoxifying role of GST genes in D. citri is unavailable. Via a sequence homology search, we isolated and characterized three DcGST genes (DcGSTd1, DcGSTe1 and DcGSTe2) from D. citri. Phylogenetic analysis grouped DcGSTd1 into the delta class of GST genes, whereas DcGSTe1 and DcGSTe2 were clustered in the epsilon clade. Gene expression analysis revealed that chlorpyrifos treatment increased the mRNA levels of DcGSTe1 and fenpropathrin enhanced the expression level of DcGSTd1, while DcGSTe2 was significantly up-regulated after exposure to thiamethoxam at a dose of 30% lethal concentration (LC30). RNA interference (RNAi) of DcGSTe2 and DcGSTd1 followed by an insecticide bioassay increased the mortalities of thiamethoxam-treated psyllids by 23.0% and fenpropathrin-treated psyllids by 15.0%. In contrast, knockdown of DcGSTe1 did not significantly increase the susceptibility of D. citri to any of these three insecticides. Further, feeding with double-stranded RNA (dsDcGSTe2-d1) interfusion co-silenced DcGSTe2 and DcGSTd1 expression in D. citri, and led to an increase of susceptibility to both fenpropathrin and thiamethoxam. The findings suggest that DcGSTe2 and DcGSTd1 play unique roles in detoxification of the pesticides thiamethoxam and fenpropathrin. In addition, co-silencing by creating a well-designed dsRNA interfusion against multiple genes was a good RNAi strategy in D. citri. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Hierarchical Velocity Control Based on Differential Flatness for a DC/DC Buck Converter-DC Motor System

Directory of Open Access Journals (Sweden)

R. Silva-Ortigoza

2014-01-01

Full Text Available This paper presents a hierarchical controller that carries out the angular velocity trajectory tracking task for a DC motor driven by a DC/DC Buck converter. The high level control is related to the DC motor and the low level control is dedicated to the DC/DC Buck converter; both controls are designed via differential flatness. The high level control provides a desired voltage profile for the DC motor to achieve the tracking of a desired angular velocity trajectory. Then, a low level control is designed to ensure that the output voltage of the DC/DC Buck converter tracks the voltage profile imposed by the high level control. In order to experimentally verify the hierarchical controller performance, a DS1104 electronic board from dSPACE and Matlab-Simulink are used. The switched implementation of the hierarchical average controller is accomplished by means of pulse width modulation. Experimental results of the hierarchical controller for the velocity trajectory tracking task show good performance and robustness against the uncertainties associated with different system parameters.

An Integrated Multifunctional Bidirectional AC/DC and DC/DC Converter for Electric Vehicles Applications

OpenAIRE

Liwen Pan; Chengning Zhang

2016-01-01

This paper presents an on-board vehicular battery charger that integrates bidirectional AC/DC converter and DC/DC converter to achieve high power density for application in electric vehicles (EVs). The integrated charger is able to transfer electrical energy between the battery pack and the electric traction system and to function as an AC/DC battery charger. The integrated charger topology is presented and the design of passive components is discussed. The control schemes are developed for m...

PENGGUNAAN FUZZY LOGIC UNTUK KONTROL PARALLEL CONVERTER DC-DC

Directory of Open Access Journals (Sweden)

Bambang Prio Hartono

2012-09-01

Full Text Available Abstract: Using system fuzzy logic as control  technology have been used on low load dc-dc converter with combined parallel compiled  dc-dc converter can  obtain big load.   With existence of differrence of component parameter and each parallel compiled converter can obtained different current  and voltage output.  Function of controller  for to do adjustment, so that current which is applied  to  load by each converter  can be obtained  difference error as small as possible or same. The object of research is developing design of large signal dc-dc converter which is  combined with using  FLC so that  obtain  better performance.  To get better performance have been made plant model and simulation with CDE method.  The more systematic  system and design is needed to overcome bigger load  on dc-dc converter, so that parallel  compiled current master slave control system on dc-dc converter with using fuzzy logic  controller is used. Result of  research showed that error or difference of  current  which is applied to load can handled by fuzzy logic  controller.  Technic of current and voltage controller co to do adjustment current and voltage distribution  equally to load.  Distribution of iL1,iL2 and  output voltage Vo on dc-dc  converter with load 2,25 until  7,875 and voltage  100  until 120 volt,  load current beetwen  12 until 48, % relatif  error  Vo  0,4% until  0,9%.

Full range ZVS DC-DC converter

International Nuclear Information System (INIS)

Upadhyay, Rinki; Badapanda, M.K.; Hannurkar, P.R.

2011-01-01

A 500 V, 24 Amp DC-DC converter with digital signal processor (DSP) based control and protection has been designed, fabricated and tested. Its power circuit consists of IGBT based single phase inverter bridge, ferrite transformer and diode rectifier. All IGBTs in the inverter bridge are operated in zero voltage switching (ZVS) mode to minimize switching losses thereby increasing the efficiency of the converter significantly. The efficiency of this converter is measured to be greater than 97% at full load. In a conventional full bridge inverter, typically ZVS is achieved under full load condition while at light load ZVS is lost. An auxiliary LC circuit has been intentionally incorporated in this converter to achieve ZVS even at light loaded conditions. Detailed simulation of the converter circuit is carried out and crucial waveforms have been presented in this paper. Microchip make dsPIC30F2020 DSP is employed to provide phase shifted PWMs to IGBTs in the inverter bridge. All the crucial parameters are also monitored by this DSP and in case of any unfavorable conditions, the converter is tripped off. Suitable experiments were carried out in this DC-DC converter under different loaded conditions and a close match between the simulated and experimental results were obtained. Such DC-DC converters can be connected in series or parallel for the development of solid state modular power supplies for various applications. (author)

Influence of reactive gas admixture on transition metal cluster nucleation in a gas aggregation cluster source

Science.gov (United States)

Peter, Tilo; Polonskyi, Oleksandr; Gojdka, Björn; Mohammad Ahadi, Amir; Strunskus, Thomas; Zaporojtchenko, Vladimir; Biederman, Hynek; Faupel, Franz

2012-12-01

We quantitatively assessed the influence of reactive gases on the formation processes of transition metal clusters in a gas aggregation cluster source. A cluster source based on a 2 in. magnetron is used to study the production rate of titanium and cobalt clusters. Argon served as working gas for the DC magnetron discharge, and a small amount of reactive gas (oxygen and nitrogen) is added to promote reactive cluster formation. We found that the cluster production rate depends strongly on the reactive gas concentration for very small amounts of reactive gas (less than 0.1% of total working gas), and no cluster formation takes place in the absence of reactive species. The influence of discharge power, reactive gas concentration, and working gas pressure are investigated using a quartz micro balance in a time resolved manner. The strong influence of reactive gas is explained by a more efficient formation of nucleation seeds for metal-oxide or nitride than for pure metal.

TOPOLOGICAL REVIEW AND ANALYSIS OF DC-DC BOOST CONVERTERS

Directory of Open Access Journals (Sweden)

V. INDRA GANDHI

2017-06-01

Full Text Available DC voltage boost up is essential in numerous applications; especially considering Photovoltaic (PV based renewable power generation system. The conventional DC-DC boost converter is the most admired configuration for this scheme, even if the converter efficiency is restricted at duty cycle near to maximum value. In order to find solution to the problem and improve its conversion capability, many converter configurations have been implemented so far. With this circumstance, this research work proposes to give overview of a few most imperative research works related to DC-DC boost converters. Some configurations are covered and classified basically based on the application. The major benefits and disadvantages related to the available techniques are also briefly conveyed. At last, a proper evaluation is recognized among the important types of DC-DC boost converters in terms of efficiency, number of components, and stability.

DC/DC converters for integration of double-layer condensers in onboard power supply; DC/DC-Wandler zur Einbindung von Doppelschichtkondensatoren in das Fahrzeugenergiebordnetz

Energy Technology Data Exchange (ETDEWEB)

Polenov, Dieter

2010-01-15

The paper discusses DC/DC converters for integration of double layer condensers into the onboard power system. First, requirements on DC/DC converters are listed and compared on the basis of three exemplary applications. A DC/DC converter concept is developed for decoupling transient high-power loads like electric steering systems. Three different topologies are compared using a specially developed method in order to find the best solution for the given application. In order to establish adequate criteria for selecting the switching frequency and inductivities of storage throttles, the influence of the trottle power change on the switching characteristics of the MOSFETs and on certain ranges of EMP interference emissions is investigated. As methods of optimising the operation of the synchronous rectifiers, parallel connection of Schottky diodes and synchronous rectifiers as well as the variation of the shut-off dead times of synchronous rectifiers were investigated. Further, a concept for converter control was developed in consideration of the intended application and topology. Finally, selected aspects for implementation of the DC/DC converter concept are presented as well as the results of experimental investigations.

Chaos analysis and chaotic EMI suppression of DC-DC converters

CERN Document Server

Zhang, Bo

2014-01-01

Introduces chaos theory, its analytical methods and the means to apply chaos to the switching power supply design DC-DC converters are typical switching systems which have plenty of nonlinear behaviors, such as bifurcation and chaos. The nonlinear behaviors of DC-DC converters have been studied heavily over the past 20 years, yet researchers are still unsure of the practical application of bifurcations and chaos in switching converters. The electromagnetic interference (EMI), which resulted from the high rates of changes of voltage and current, has become a major design criterion in DC-DC co

Thermalhydraulic experiments with a cluster of 19 rods roughened by a novel type of roughness

International Nuclear Information System (INIS)

Rehme, K.; Kernforschungszentrum Karlsruhe G.m.b.H.

1981-02-01

Distributions of temperature and pressure were measured on cluster of 19 electrically heated tubes. 400 thermocouples were used for temperature measurements. The tubes were partly roughened by a novel type of roughness with a thermal performance superior to that of transverse ribs. The experiments bot with helium and nitrogen as coolants covered a range of Reynolds numbers between 450 and 1.8 x 10 5 . The maximum linear rod power achived was 43 kWm -1 , the maximum measured wall temperature 1271 K (998 0 C). The report contains the description of the test section together with all tabulated results. (orig.) [de

Full wave dc-to-dc converter using energy storage transformers

Science.gov (United States)

Moore, E. T.; Wilson, T. G.

1969-01-01

Full wave dc-to-dc converter, for an ion thrustor, uses energy storage transformers to provide a method of dc-to-dc conversion and regulation. The converter has a high degree of physical simplicity, is lightweight and has high efficiency.

Pulsewidth modulated DC-to-DC power conversion circuits, dynamics, and control designs

CERN Document Server

Choi, Byungcho

2013-01-01

This is the definitive reference for anyone involved in pulsewidth modulated DC-to-DC power conversion Pulsewidth Modulated DC-to-DC Power Conversion: Circuits, Dynamics, and Control Designs provides engineers, researchers, and students in the power electronics field with comprehensive and complete guidance to understanding pulsewidth modulated (PWM) DC-to-DC power converters. Presented in three parts, the book addresses the circuitry and operation of PWM DC-to-DC converters and their dynamic characteristics, along with in-depth discussions of control design of PWM DC-to

Triple voltage dc-to-dc converter and method

Science.gov (United States)

Su, Gui-Jia

2008-08-05

A circuit and method of providing three dc voltage buses and transforming power between a low voltage dc converter and a high voltage dc converter, by coupling a primary dc power circuit and a secondary dc power circuit through an isolation transformer; providing the gating signals to power semiconductor switches in the primary and secondary circuits to control power flow between the primary and secondary circuits and by controlling a phase shift between the primary voltage and the secondary voltage. The primary dc power circuit and the secondary dc power circuit each further comprising at least two tank capacitances arranged in series as a tank leg, at least two resonant switching devices arranged in series with each other and arranged in parallel with the tank leg, and at least one voltage source arranged in parallel with the tank leg and the resonant switching devices, said resonant switching devices including power semiconductor switches that are operated by gating signals. Additional embodiments having a center-tapped battery on the low voltage side and a plurality of modules on both the low voltage side and the high voltage side are also disclosed for the purpose of reducing ripple current and for reducing the size of the components.

The Influence of Social Network Characteristics on Peer Clustering in Smoking: A Two-Wave Panel Study of 19- and 23-Year-Old Swedes.

Science.gov (United States)

Miething, Alexander; Rostila, Mikael; Edling, Christofer; Rydgren, Jens

2016-01-01

The present study examines how the composition of social networks and perceived relationship content influence peer clustering in smoking, and how the association changes during the transition from late adolescence to early adulthood. The analysis was based on a Swedish two-wave survey sample comprising ego-centric network data. Respondents were 19 years old in the initial wave, and 23 when the follow-up sample was conducted. 17,227 ego-alter dyads were included in the analyses, which corresponds to an average response rate of 48.7 percent. Random effects logistic regression models were performed to calculate gender-specific average marginal effects of social network characteristics on smoking. The association of egos' and alters' smoking behavior was confirmed and found to be stronger when correlated in the female sample. For females, the associations decreased between age 19 and 23. Interactions between network characteristics and peer clustering in smoking showed that intense social interactions with smokers increase egos' smoking probability. The influence of network structures on peer clustering in smoking decreased during the transition from late adolescence to early adulthood. The study confirmed peer clustering in smoking and revealed that females' smoking behavior in particular is determined by social interactions. Female smokers' propensity to interact with other smokers was found to be associated with the quality of peer relationships, frequent social interactions, and network density. The influence of social networks on peer clustering in smoking decreased during the transition from late adolescence to early adulthood.

Switching coordination of distributed dc-dc converters for highly efficient photovoltaic power plants

Science.gov (United States)

Agamy, Mohammed; Elasser, Ahmed; Sabate, Juan Antonio; Galbraith, Anthony William; Harfman Todorovic, Maja

2014-09-09

A distributed photovoltaic (PV) power plant includes a plurality of distributed dc-dc converters. The dc-dc converters are configured to switch in coordination with one another such that at least one dc-dc converter transfers power to a common dc-bus based upon the total system power available from one or more corresponding strings of PV modules. Due to the coordinated switching of the dc-dc converters, each dc-dc converter transferring power to the common dc-bus continues to operate within its optimal efficiency range as well as to optimize the maximum power point tracking in order to increase the energy yield of the PV power plant.

Research borehole drilling activity for boreholes DH-18, DH-19, DC-12, DC-13, DC-14, DC-15, and deepening of existing borehole DC-7

International Nuclear Information System (INIS)

1979-09-01

This report is an environmental evaluation of the impacts of proposed borehole drilling activities at the Hanford Site, northwest of Richland, Washington. The proposed action is to drill six research boreholes ranging in depth from 137 to 1372 meters (m) [250 to 4500 +- feet (ft)]. In addition, an existing borehole (DC-7) will be extended from 1249 to 1524 m (4099 to 5000 +- ft). The purpose of the US Department of Energy's (DOE) borehole drilling activities is to collect data on in situ rock formations that are considered potentialy suitable for nuclear waste repositories. The technical program efforts necessary to identify and qualify specific underground waste facility sites in candidate rock formations include geologic and hydrologic studies (seismicity and tectonics, rock structure and stratigraphy, lithology, etc.). Borehole drilling is an integral part of the geological studies and is essential to a thorough understanding of potentially suitable geologic formations. The purpose of the proposed drilling activities is to obtain data for evaluating Columbia River basalts that are being evaluated by the National Waste Terminal Storage (NWTS) Program to determine their suitability potential for nuclear waste repositories. Unavoidable impact to the environment is limited primarily to the clearing of land needed for access and drilling operations. Considerations exercised during site preparation, drilling, and subsequent site restoration will limit modification of the natural environment to the minimum required for accomplishment of test objectives

The performance of the DC motor by the PID controlling PWM DC-DC boost converter

OpenAIRE

Can, Erol; Sayan, Hasan Hüseyin

2017-01-01

This paper presents the PID controlling direct current (DC) to the direct current boost converter feds DC motor which has a 3.68 kW and 240 V of DC voltage input on its characteristics. What is first formed is the boost converter mathematical model at the design stage. Secondly, a mathematical model of the DC motor is created so that the boost converter with the machine can be established and modeled at the Matlab Simulink. The PID controller is considered for arranging a pulse width modulati...

On and off controlled resonant dc-dc power converter

DEFF Research Database (Denmark)

2015-01-01

The present invention relates to a resonant DC-DC power converter comprising an input side circuit comprising a positive and a negative input terminal for receipt of an input voltage or current and an output side circuit comprising positive and negative output terminals for supply of a converter...... output voltage and connection to a converter load. The resonant DC-DC power converter further comprises a rectification circuit connected between an output of a resonant network and the output side circuit. The resonant network is configured for alternatingly being charged from the input voltage...... or current and discharged through the rectification circuit by a first controllable switch arrangement in accordance with a first switch control signal. A second controllable switch arrangement of the resonant DC-DC power converter is configured to select a first impedance characteristic of the resonant...

The Topologies Research of a Soft Switching Bidirectional DC/DC Converter

DEFF Research Database (Denmark)

Zhang, Qi; Zhang, Yongping; Sun, Xiangdong

2017-01-01

A soft-switching solution implemented to the traditional bidirectional DC/DC converter is developed. The soft-switching cell, which composed of three auxiliary switches, one resonant capacitor and one resonant inductor, is equipped in the traditional bidirectional DC/DC converter to realize circuit...... circle. And the proposed topology of bidirectional soft-switching dc-dc converter(TASBC) performs ideal soft switching at boost operations. The characteristics of the proposed converter has been verified by MATLAB simulations and experimental results....

75 FR 27401 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-9-30, DC-9-40, and DC-9-50...

Science.gov (United States)

2010-05-17

... Airworthiness Directives; McDonnell Douglas Corporation Model DC- 9-30, DC-9-40, and DC-9-50 Series Airplanes... airworthiness directive (AD) for certain Model DC-9-30, DC-9-40, and DC-9-50 series airplanes. This AD requires... this AD to detect and correct the potential for an arc/spark condition to occur within the fuel boost...

A Feed-Forward Control Realizing Fast Response for Three-Branch Interleaved DC-DC Converter in DC Microgrid

Directory of Open Access Journals (Sweden)

Haojie Wang

2016-07-01

Full Text Available It is a common practice for storage batteries to be connected to DC microgrid buses through DC-DC converters for voltage support on islanded operation mode. A feed-forward control based dual-loop constant voltage PI control for three-branch interleaved DC-DC converters (TIDC is proposed for storage batteries in DC microgrids. The working principle of TIDC is analyzed, and the factors influencing the response rate based on the dual-loop constant voltage control for TIDC are discussed, and then the method of feed-forward control for TIDC is studied to improve the response rate for load changing. A prototype of the TIDC is developed and an experimental platform is built. The experiment results show that DC bus voltage sags or swells caused by load changing can be reduced and the time for voltage recovery can be decreased significantly with the proposed feed-forward control.

A Feed-Forward Control Realizing Fast Response for Three-Branch Interleaved DC-DC Converter in DC Microgrid

DEFF Research Database (Denmark)

Wang, Haojie; Han, Minxiao; Yan, Wenli

2016-01-01

It is a common practice for storage batteries to be connected to DC microgrid buses through DC-DC converters for voltage support on islanded operation mode. A feed-forward control based dual-loop constant voltage PI control for three-branch interleaved DC-DC converters (TIDC) is proposed...... for storage batteries in DC microgrids. The working principle of TIDC is analyzed, and the factors influencing the response rate based on the dual-loop constant voltage control for TIDC are discussed, and then the method of feed-forward control for TIDC is studied to improve the response rate for load...... changing. A prototype of the TIDC is developed and an experimental platform is built. The experiment results show that DC bus voltage sags or swells caused by load changing can be reduced and the time for voltage recovery can be decreased significantly with the proposed feed-forward control....

Delineating a road-salt plume in lakebed sediments using electrical resistivity, piezometers, and seepage meters at Mirror Lake, New Hampshire, U.S.A

Science.gov (United States)

Toran, Laura; Johnson, Melanie; Nyquist, Jonathan E.; Rosenberry, Donald O.

2010-01-01

Electrical-resistivity surveys, seepage meter measurements, and drive-point piezometers have been used to characterize chloride-enriched groundwater in lakebed sediments of Mirror Lake, New Hampshire, U.S.A. A combination of bottom-cable and floating-cable electrical-resistivity surveys identified a conductive zone (ohm-m)">(ohm-m)(ohm-m) overlying resistive bedrock (ohm-m)">(ohm-m)(ohm-m)beneath the lake. Shallow pore-water samples from piezometers in lakebed sediments have chloride concentrations of 200–1800μeq/liter">200–1800μeq/liter200–1800μeq/liter, and lake water has a chloride concentration of 104μeq/liter">104μeq/liter104μeq/liter. The extent of the plume was estimated and mapped using resistivity and water-sample data. The plume (20×35m">20×35m20×35m wide and at least 3m">3m3m thick) extends nearly the full length and width of a small inlet, overlying the top of a basin formed by the bedrock. It would not have been possible to mapthe plume's shape without the resistivity surveys because wells provided only limited coverage. Seepage meters were installed approximately 40m">40m40m from the mouth of a small stream discharging at the head of the inlet in an area where the resistivity data indicated lake sediments are thin. These meters recorded in-seepage of chloride-enriched groundwater at rates similar to those observed closer to shore, which was unexpected because seepage usually declines away from shore. Although the concentration of road salt in the northeast inlet stream is declining, the plume map and seepage data indicate the groundwater contribution of road salt to the lake is not declining. The findings demonstrate the benefit of combining geophysical and hydrologic data to characterize discharge of a plume beneath Mirror Lake. The extent of the plume in groundwater beneath the lake and stream indicate there will likely be a long-term source of chloride to the lake from groundwater.

Using PBL to Improve Educational Outcomes and Student Satisfaction in the Teaching of DC/DC and DC/AC Converters

Science.gov (United States)

Martinez-Rodrigo, Fernando; Herrero-De Lucas, Luis Carlos; de Pablo, Santiago; Rey-Boue, Alexis B.

2017-01-01

This paper examines the question of how to use project-based learning to increase student performance and satisfaction in a power electronics course addressing the topics of dc/dc and dc/ac converters, the assembly of a dc/dc converter, and the use of a commercial speed drive. A detailed presentation of the methodology is shown, and the results…

Improved Control Strategy for T-type Isolated DC/DC Converters

DEFF Research Database (Denmark)

Liu, Dong; Deng, Fujin; Wang, Yanbo

2017-01-01

T-type isolated DC/DC converters have recently attracted attention due to their numerous advantages, including few components, low cost, and symmetrical operation of transformers. This study proposes an improved control strategy for increasing the efficiency of T-type isolated DC/DC converters....... Under the proposed strategy, the primary circulating current flows through the auxiliary switches (metal–oxide–semiconductor field-effect transistors) instead of their body diodes in free-wheeling periods. Such feature can reduce conduction losses, thereby improving the efficiency of T-type isolated DC...

Investigation of clustering effects in the reaction pp→ppπ+π+π-π- at 19 GeV/c

International Nuclear Information System (INIS)

Allan, J.; Blomqvist, G.

1975-07-01

Possible production of high multiplicity clusters of secondaries in the reaction pp→ppπ + π + π - π - at 19 GeV/c is investigated. The experimental distribution of dispersion versus mean for the pion rapidities shows, compared to simple one component models, an excess of events in the regions where a single diffraction dissociation process is expected to populate. A method based on the Cramer van Mises statistical test combined with an operational method for selection of quasi two body reactions is used for investigation of clustering effects in phase space caused by different reaction mechanisms. The analysis indicates that the distribution of experimental events in phase space has mainly two population centers, one consisting of events with the kinematical configuration expected from a single diffraction dissociation process. (Auth.)

High power density dc/dc converter: Selection of converter topology

Science.gov (United States)

Divan, Deepakraj M.

1990-01-01

The work involved in the identification and selection of a suitable converter topology is described. Three new dc/dc converter topologies are proposed: Phase-Shifted Single Active Bridge DC/DC Converter; Single Phase Dual Active Bridges DC/DC Converter; and Three Phase Dual Active Bridges DC/DC Converter (Topology C). The salient features of these topologies are: (1) All are minimal in structure, i.e., each consists of an input and output bridge, input and output filter and a transformer, all components essential for a high power dc/dc conversion process; (2) All devices of both the bridges can operate under near zero-voltage conditions, making possible a reduction of device switching losses and hence, an increase in switching frequency; (3) All circuits operate at a constant frequency, thus simplifying the task of the magnetic and filter elements; (4) Since, the leakage inductance of the transformer is used as the main current transfer element, problems associated with the diode reverse recovery are eliminated. Also, this mode of operation allows easy paralleling of multiple modules for extending the power capacity of the system; (5) All circuits are least sensitive to parasitic impedances, infact the parasitics are efficently utilized; and (6) The soft switching transitions, result in low electromagnetic interference. A detailed analysis of each topology was carried out. Based on the analysis, the various device and component ratings for each topology operating at an optimum point, and under the given specifications, are tabulated and discussed.

An Integrated Multifunctional Bidirectional AC/DC and DC/DC Converter for Electric Vehicles Applications

Directory of Open Access Journals (Sweden)

Liwen Pan

2016-06-01

Full Text Available This paper presents an on-board vehicular battery charger that integrates bidirectional AC/DC converter and DC/DC converter to achieve high power density for application in electric vehicles (EVs. The integrated charger is able to transfer electrical energy between the battery pack and the electric traction system and to function as an AC/DC battery charger. The integrated charger topology is presented and the design of passive components is discussed. The control schemes are developed for motor drive system and battery-charging system with a power pulsation reduction circuit. Simulation results in MATLAB/Simulink and experiments on a 30-kW motor drive and 3.3-kW AC/DC charging prototype validate the performance of the proposed technology. In addition, power losses, efficiency comparison and thermal stress for the integrated charger are illustrated. The results of the analyses show the validity of the advanced integrated charger for electric vehicles.

Fracture hydraulic conductivity in the Mexico City clayey aquitard: Field piezometer rising-head tests

Science.gov (United States)

Vargas, Carlos; Ortega-Guerrero, Adrián

A regional lacustrine aquitard covers the main aquifer of the metropolitan area of Mexico City. The aquitard's hydraulic conductivity (K') is fundamental for evaluating the natural protection of the aquifer against a variety of contaminants present on the surface and its hydraulic response. This study analyzes the distribution and variation of K' in the plains of Chalco, Texcoco and Mexico City (three of the six former lakes that existed in the Basin of Mexico), on the basis of 225 field-permeability tests, in nests of existing piezometers located at depths of 2-85 m. Tests were interpreted using the Hvorslev method and some by the Bouwer-Rice method. Results indicate that the distribution of K' fits log-Gaussian regression models. Dominant frequencies for K' in the Chalco and Texcoco plains range between 1E-09 and 1E-08 m/s, with similar population means of 1.19E-09 and 1.7E-09 m/s, respectively, which are one to two orders of magnitude higher than the matrix conductivity. In the Mexico City Plain the population mean is near by one order of magnitude lower; K'=2.6E-10 m/s. The contrast between the measured K' and that of the matrix is attributed to the presence of fractures in the upper 25-40 m, which is consistent with the findings of previous studies on solute migration in the aquitard. Un imperméable régional d'origine lacustre recouvre le principal aquifère de la zone urbaine de la ville de Mexico. La conductivité hydraulique K' de cet imperméable est fondamentale pour évaluer la protection naturelle de l'aquifère, contre les différents contaminants présents en surface, et sa réponse hydraulique. Cette étude analyse et les variations de K' dans les plaines de Chalco, Texcoco et Mexico (trois des six anciens lacs qui existaient dans le Bassin de Mexico), sur la base de 225 essais de perméabilité sur le terrain, réalisés en grappes dans des piézomètres existants entre 2 et 85 m de profondeur. Les essais ont été interprétés avec la m

RESONANT STEP-DOWN DC-DC POWER CONVERTERS

DEFF Research Database (Denmark)

2015-01-01

The present invention relates to a resonant step-down DC-DC power converter which comprises a primary side circuit and a secondary side circuit coupled through a galvanic isolation barrier. The primary side circuit comprises a positive and a negative input terminal for receipt of an input voltage...... charged from the input voltage and discharged to the output capacitor through the galvanic isolation barrier by a semiconductor switch arrangement in accordance with a switch control signal to produce the converter output voltage. The resonant step-down DC-DC power converter comprises an electrical short......-circuit connection across the galvanic isolation barrier connecting, in a first case, the second negative electrode of the output capacitor to the positive input terminal of the primary side circuit or, in a second case, connecting the second positive electrode of the output capacitor to the negative input terminal...

Atmel Microcontroller Based Soft Switched PWM ZVS Full Bridge DC to DC Converter

Directory of Open Access Journals (Sweden)

DEEPAK KUMAR NAYAK

2010-12-01

Full Text Available This paper deals with the simulation and implementation of soft switched PWM ZVS full bridge DC to DC converter. The 48V DC is efficiently reduced to 12V DC using a DC to DC converter. This converter has advantages like reduced switching losses, stresses and EMI. Input DC is converted into high frequency AC and it is stepped down to 12V level. Later it is rectified using a full wave rectifier. Laboratory model of microcontroller based DC to DC converter is fabricated and tested. The experimental results are compared with the simulation results.

Quasi-Z-Source Half-Bridge DC-DC Converter for Photovoltaic Applications

OpenAIRE

Vinnikov, D; Chub, A; Husev, O; Zaķis, J

2015-01-01

This paper presents a novel quasi-Z-source halfbridge galvanically isolated DC-DC converter intended for the photovoltaic applications. The topology could be envisioned as an alternative to the boost half-bridge DC-DC converter but the benefit of its symmetric structure reduces the threat of transformer saturation due to the dc flux. The proposed converter features the continuous input current and could be used either with one or two input voltage sources.

DC motor operation controlled from a DC/DC power converter in pulse mode with low duty cycle

OpenAIRE

Stefanov, Goce; Kukuseva, Maja; Citkuseva Dimitrovska, Biljana

2016-01-01

In this paper pulse mode of operation of DC motor controlled by DC/DC power converter is analyzed. DC motor operation with time intervals in which the motor operates without output load is of interest. In this mode it is possible the motor to restore energy. Also, in the paper are represented calculations for the amount of the restored energy in the pulse mode operation of the motor for different duty cycles.

Control of the DC-DC Converter used into Energy Generation System

International Nuclear Information System (INIS)

Bizon, Nicu; Oproescu, Mihai

2006-01-01

This paper presents an investigation of the DC-DC Converter controller used into Energy Generation System. The full bridge is used into an Energy Generation System (EGS) as second power interface between the energy source and the high DC bus. The simulation results show that the DC-DC Converter behavior can be improved using a well designed PI control surface. The used Simulink models for the EGS blocks and some design considerations are presented, too. (authors)

miR-19, a component of the oncogenic miR-17∼92 cluster, targets the DNA-end resection factor CtIP

DEFF Research Database (Denmark)

Hühn, D; Kousholt, A N; Sørensen, Claus Storgaard

2014-01-01

MicroRNA-19 (miR-19) was recently identified as the key oncogenic component of the polycistronic miR-17∼92 cluster, also known as oncomiR-1, which is frequently upregulated or amplified in multiple tumor types. However, the gene targets and the pathways underlying the tumor-promoting activity of mi......R-19 still remain largely elusive. CtIP/RBBP8 promotes DNA-end resection, a critical step in the repair of DNA double-strand breaks (DSBs) by homologous recombination (HR), and is considered to function as a tumor suppressor. In this study, we show that miR-19 downregulates CtIP expression by binding...... to two highly conserved sequences located in the 3'-untranslated region of CtIP mRNA. We further demonstrate that CtIP expression is repressed by miR-19 during continuous genotoxic stress in a p53-dependent manner. Finally, we report that miR-19 impairs CtIP-mediated DNA-end resection, which results...

Novel composite resonance DC-DC converter with voltage doubler rectifier

OpenAIRE

Kato, Hisatsugu; Matsuo, Hirohumi; Eguchi, Masaki; Sakamoto, Yukitaka; Nakaishi, Masaki

2009-01-01

This paper deals with a novel composite resonance DC-DC converter with the voltage doubler rectifier, which is developed to be applied to the power conditioner of the photovoltaic generation system. The proposed DC-DC converter has the current and voltage resonance functions. Therefore, the output voltage regulation can be achieved for the large variations of the input voltage and load. Also, this converter has the high power efficiency. The maximum power efficiency 96.1% can be realized.

Ultra-high Efficiency DC-DC Converter using GaN Devices

DEFF Research Database (Denmark)

Ramachandran, Rakesh

2016-01-01

properties of GaN devices can be utilized in power converters to make them more compact and highly efficient. This thesis entitled “Ultra-high Efficiency DC-DC Converter using GaN devices” focuses on achieving ultra-high conversion efficiency in an isolated dc-dc converter by the optimal utilization of Ga...... for many decades. However, the rate of improvement slowed as the silicon power materials asymptotically approached its theoretical bounds. Compared to Si, wideband gap materials such as Silicon Carbide (SiC) and Gallium Nitride (GaN) are promising semiconductors for power devices due to their superior...... in this thesis. Efficiency measurements from the hardware prototype of both the topologies are also presented in this thesis. Finally, the bidirectional operation of an optimized isolated dc-dc converter is presented. The optimized converter has achieved an ultra-high efficiency of 98.8% in both directions...

Morphology and magnetism of Fe monolayers and small Fen clusters (n 2-19) supported on the Ni(111) surface

International Nuclear Information System (INIS)

Longo, R C; MartInez, E; Dieguez, O; Vega, A; Gallego, L J

2007-01-01

Using the modified embedded atom model in conjunction with a self-consistent tight-binding method, we investigated the lowest-energy structures of Fe monolayers and isolated Fe n clusters (n = 2-19) supported on the Ni(111) surface. In keeping with experimental findings, our calculations predict that the atoms of the monolayer occupy face-centred cubic (fcc) rather than hexagonal close-packed (hcp) sites. Likewise in agreement with experiment we found that Fe layers stack with a pseudomorphic fcc structure up to two monolayers, beyond which they stack as bcc(110). The structures of supported Fe clusters are predicted to be two-dimensional islands maximizing the number of nearest-neighbour bonds among the adsorbed Fe atoms, and their average magnetic moments per atom decrease towards that of the supported Fe monolayer almost monotonically as n increases. Finally, a pair of Fe 3 clusters on Ni(111) were found to exhibit virtually no interaction with each other even when separated by only one atomic row, i.e. so long as they do not coalesce they retain their individual magnetic properties

75 FR 61352 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-30, DC-10-30F, DC-10-30F (KC...

Science.gov (United States)

2010-10-05

... Airworthiness Directives; McDonnell Douglas Corporation Model DC- 10-30, DC-10-30F, DC-10-30F (KC-10A and KDC-10...-13 McDonnell Douglas Corporation: Amendment 39-16448; Docket No. FAA-2010-0553; Directorate.... Applicability (c) This AD applies to McDonnell Douglas Corporation Model DC- 10-30, DC-10-30F, DC-10-30F (KC-10A...

Sliding-Mode Control of a Charger/Discharger DC/DC Converter for DC-Bus Regulation in Renewable Power Systems

Directory of Open Access Journals (Sweden)

Sergio Ignacio Serna-Garcés

2016-03-01

Full Text Available Stand-alone power systems based on renewable energy sources are used to replace generators based on fossil fuels. Those renewable power systems also require Energy Storage Devices (ESD interfaced by a charger/discharger power converter, which consist of a bidirectional DC/DC converter, and a DC bus. This paper proposes a single sliding-mode controller (SMC for the charger/discharger DC/DC converter to provide a stable DC bus voltage in any operation condition: charging or discharging the ESD, or even without any power exchange between the ESD and the DC bus. Due to the non-linear nature of the power converter, the SMC parameters are adapted on-line to ensure global stability in any operation condition. Such stability of the adaptive SMC is mathematically demonstrated using analytical expressions for the transversality, reachability and equivalent control conditions. Moreover, a design procedure for the adaptive SMC parameters is provided in order to ensure the dynamic response required for the correct operation of the load. Finally, simulations and experimental tests validate the proposed controller and design procedure.

Design and Analysis of Two-Phase Boost DC-DC Converter

OpenAIRE

Taufik Taufik; Tadeus Gunawan; Dale Dolan; Makbul Anwari

2010-01-01

Multiphasing of dc-dc converters has been known to give technical and economical benefits to low voltage high power buck regulator modules. A major advantage of multiphasing dc-dc converters is the improvement of input and output performances in the buck converter. From this aspect, a potential use would be in renewable energy where power quality plays an important factor. This paper presents the design of a 2-phase 200W boost converter for battery charging application. Analysis of results fr...

Strong lensing analysis of PLCK G004.5-19.5, a Planck-discovered cluster hosting a radio relic at z = 0.52

Science.gov (United States)

Sifón, Cristóbal; Menanteau, Felipe; Hughes, John P.; Carrasco, Mauricio; Barrientos, L. Felipe

2014-02-01

Context. The recent discovery of a large number of galaxy clusters using the Sunyaev-Zel'dovich (SZ) effect has opened a new era on the study of the most massive clusters in the Universe. Multiwavelength analyses are required to understand the properties of these new sets of clusters, which are a sensitive probe of cosmology. Aims: We aim for a multiwavelength characterization of PLCK G004.5-19.5, one of the most massive X-ray validated SZ effect-selected galaxy clusters discovered by the Planck satellite. Methods: We have observed PLCK G004.5-19.5 with GMOS on the 8.1 m-Gemini South Telescope for optical imaging and spectroscopy, and performed a strong lensing analysis. We also searched for associated radio emission in published catalogs. Results: An analysis of the optical images confirms that this is a massive cluster, with a dominant central galaxy and an accompanying red sequence of galaxies, plus a 14″-long strong lensing arc. Longslit spectroscopy of six cluster members shows that the cluster is at z = 0.516 ± 0.002. We also targeted the strongly lensed arc, and found zarc = 1.601. We use LensTool to carry out a strong lensing analysis, from which we measure a median Einstein radius θE(zs = 1.6) ≃ 30″ and estimate an enclosed mass ME = 2.45-0.47+0.45 × 1014 M⊙. By extrapolating a Navarro-Frenk-White profile, we find a total mass M500SL = 4.0-1.0+2.1 × 1014 M⊙. We also include a constraint on the mass from previous X-ray observations, which yields a slightly higher mass, M500SL+X = 6.7-1.3+2.6 × 1014 M⊙, consistent with the value from strong lensing alone. Intermediate-resolution radio images from the TIFR GMRT Sky Survey at 150 MHz reveal that PLCK G004.5-19.5 hosts a powerful radio relic on scales ≲500 kpc. Emission at the same location is also detected in low-resolution images at 843 MHz and 1.4 GHz. This is one of the higher redshift radio relics known to date. Based on observations obtained at the Gemini Observatory, which is operated

SCM Handbooks for dc-to-dc Converters

Science.gov (United States)

Lee, F.; Mohmoud, M.; Yu, Y.

1984-01-01

Two documents aid in design of control modules for dc-to-dc converters. Features of SCM include: Adaptive stability, power component stress limiting, implementation of various control laws, unified design approach. Analysis and quidelines contained in handbooks enable engineer to design SCM circuit and confidently predict resulting overall performance.

Isolated step-down DC -DC converter for electric vehicles

Science.gov (United States)

Kukovinets, O. V.; Sidorov, K. M.; Yutt, V. E.

2018-02-01

Modern motor-vehicle industrial sector is moving rapidly now towards the electricity-driving cars production, improving their range and efficiency of components, and in particular the step-down DC/DC converter to supply the onboard circuit 12/24V of electric vehicle from the high-voltage battery. The purpose of this article - to identify the best circuitry topology to design an advanced step-down DC/DC converters with the smallest mass, volume, highest efficiency and power. And this will have a positive effect on driving distance of electric vehicle (EV). On the basis of computational research of existing and implemented circuit topologies of step-down DC/DC converters (serial resonant converter, full bridge with phase-shifting converter, LLC resonant converter) a comprehensive analysis was carried out on the following characteristics: specific volume, specific weight, power, efficiency. The data obtained was the basis for the best technical option - LLC resonant converter. The results can serve as a guide material in the process of components design of the traction equipment for electric vehicles, providing for the best technical solutions in the design and manufacturing of converting equipment, self-contained power supply systems and advanced driver assistance systems.

Identification of Multiple Druggable Secondary Sites by Fragment Screening against DC-SIGN.

Science.gov (United States)

Aretz, Jonas; Baukmann, Hannes; Shanina, Elena; Hanske, Jonas; Wawrzinek, Robert; Zapol'skii, Viktor A; Seeberger, Peter H; Kaufmann, Dieter E; Rademacher, Christoph

2017-06-12

DC-SIGN is a cell-surface receptor for several pathogenic threats, such as HIV, Ebola virus, or Mycobacterium tuberculosis. Multiple attempts to develop inhibitors of the underlying carbohydrate-protein interactions have been undertaken in the past fifteen years. Still, drug-like DC-SIGN ligands are sparse, which is most likely due to its hydrophilic, solvent-exposed carbohydrate-binding site. Herein, we report on a parallel fragment screening against DC-SIGN applying SPR and a reporter displacement assay, which complements previous screenings using 19 F NMR spectroscopy and chemical fragment microarrays. Hit validation by SPR and 1 H- 15 N HSQC NMR spectroscopy revealed that although no fragment bound in the primary carbohydrate site, five secondary sites are available to harbor drug-like molecules. Building on key interactions of the reported fragment hits, these pockets will be targeted in future approaches to accelerate the development of DC-SIGN inhibitors. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

75 FR 75872 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-9-30, DC-9-40, and DC-9-50...

Science.gov (United States)

2010-12-07

... Airworthiness Directives; McDonnell Douglas Corporation Model DC- 9-30, DC-9-40, and DC-9-50 Series Airplanes...: We are adopting a new airworthiness directive (AD) for the McDonnell Douglas Corporation airplanes... to include an airworthiness directive (AD) that would apply to certain McDonnell Douglas Model DC-9...

A Component-Reduced Zero-Voltage Switching Three-Level DC-DC Converter

DEFF Research Database (Denmark)

Qin, Zian; Pang, Ying; Wang, Huai

2016-01-01

The basic Zero-Voltage Switching (ZVS) three-level DC-DC converter has one clamping capacitor to realize the ZVS of the switches, and two clamping diodes to clamp the voltage of the clamping capacitor. In order to reduce the reverse recovery loss of the diode as well as its cost, this paper...... proposes to remove one of the clamping diodes in basic ZVS three-level DC-DC converter. With less components, the proposed converter can still have a stable clamping capacitor voltage, which is clamped at half of the dc link voltage. Moreover, the ZVS performance will be influenced by removing the clamping...

Active pre-filters for dc/dc Boost regulators

Directory of Open Access Journals (Sweden)

Carlos Andrés Ramos-Paja

2014-05-01

Full Text Available This paper proposes an active pre-filter to mitigate the current harmonics generated by classical dc/dc Boost regulators, which generate current ripples proportional to the duty cycle. Therefore, high output voltage conditions, i.e., high voltage conversion ratios, produce high current harmonics that must be filtered to avoid damage or source losses. Traditionally, these current components are filtered using electrolytic capacitors, which introduce reliability problems because of their high failure rate. The solution introduced in this paper instead uses a dc/dc converter based on the parallel connection of the Boost canonical cells to filter the current ripples generated by the Boost regulator, improving the system reliability. This solution provides the additional benefits of improving the overall efficiency and the voltage conversion ratio. Finally, the solution is validated with simulations and experimental results.

Laboratory manual for pulse-width modulated DC-DC power converters

CERN Document Server

Kazimierczuk, Marian K

2015-01-01

Designed to complement a range of power electronics study resources, this unique lab manual helps students to gain a deep understanding of the operation, modeling, analysis, design, and performance of pulse-width modulated (PWM) DC-DC power converters.  Exercises focus on three essential areas of power electronics: open-loop power stages; small-signal modeling, design of feedback loops and PWM DC-DC converter control schemes; and semiconductor devices such as silicon, silicon carbide and gallium nitride. Meeting the standards required by industrial employers, the lab manual combines program

A Novel PPFHB Bidirectional DC-DC Converter for Supercapacitor Application

DEFF Research Database (Denmark)

Zhang, Zhe; Thomsen, Ole Cornelius; Andersen, Michael Andreas E.

2009-01-01

This paper presents a novel bidirectional DC-DC converter for the supercapacitor application. In the proposed converter, push-pull forward with half bridge (PPFHB) voltage doubler structure is used to reduce the number of the power switches and get higher voltage gain. Based on phase-shift modula......This paper presents a novel bidirectional DC-DC converter for the supercapacitor application. In the proposed converter, push-pull forward with half bridge (PPFHB) voltage doubler structure is used to reduce the number of the power switches and get higher voltage gain. Based on phase...

Decentralized Interleaving of Paralleled Dc-Dc Buck Converters: Preprint

Energy Technology Data Exchange (ETDEWEB)

Johnson, Brian B [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rodriguez, Miguel [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sinha, Mohit [University of Minnesota; Dhople, Sairaj [University of Minnesota; Poon, Jason [University of California at Berkeley

2017-09-01

We present a decentralized control strategy that yields switch interleaving among parallel connected dc-dc buck converters without communication. The proposed method is based on the digital implementation of the dynamics of a nonlinear oscillator circuit as the controller. Each controller is fully decentralized, i.e., it only requires the locally measured output current to synthesize the pulse width modulation (PWM) carrier waveform. By virtue of the intrinsic electrical coupling between converters, the nonlinear oscillator-based controllers converge to an interleaved state with uniform phase-spacing across PWM carriers. To the knowledge of the authors, this work represents the first fully decentralized strategy for switch interleaving of paralleled dc-dc buck converters.

ASTEROSEISMOLOGY OF THE OPEN CLUSTERS NGC 6791, NGC 6811, AND NGC 6819 FROM 19 MONTHS OF KEPLER PHOTOMETRY

International Nuclear Information System (INIS)

Corsaro, Enrico; Stello, Dennis; Huber, Daniel; Bedding, Timothy R.; Benomar, Othman; White, Timothy R.; Bonanno, Alfio; Brogaard, Karsten; Kallinger, Thomas; Mosser, Benoit; Basu, Sarbani; Chaplin, William J.; Elsworth, Yvonne P.; Mathur, Savita; Christensen-Dalsgaard, Jørgen; García, Rafael A.; Hekker, Saskia; Kjeldsen, Hans; Meibom, Søren; Hall, Jennifer R.

2012-01-01

We studied solar-like oscillations in 115 red giants in the three open clusters, NGC 6791, NGC 6811, and NGC 6819, based on photometric data covering more than 19 months with NASA's Kepler space telescope. We present the asteroseismic diagrams of the asymptotic parameters δν 02 , δν 01 , and ε, which show clear correlation with fundamental stellar parameters such as mass and radius. When the stellar populations from the clusters are compared, we see evidence for a difference in mass of the red giant branch stars and possibly a difference in structure of the red clump stars, from our measurements of the small separations δν 02 and δν 01 . Ensemble échelle diagrams and upper limits to the linewidths of l = 0 modes as a function of Δν of the clusters NGC 6791 and NGC 6819 are also shown, together with the correlation between the l = 0 ridge width and the T eff of the stars. Lastly, we distinguish between red giant branch and red clump stars through the measurement of the period spacing of mixed dipole modes in 53 stars among all the three clusters to verify the stellar classification from the color-magnitude diagram. These seismic results also allow us to identify a number of special cases, including evolved blue stragglers and binaries, as well as stars in late He-core burning phases, which can be potentially interesting targets for detailed theoretical modeling.

CISH is induced during DC development and regulates DC-mediated CTL activation.

Science.gov (United States)

Miah, Mohammad Alam; Yoon, Cheol-Hee; Kim, Joonoh; Jang, Jinah; Seong, Young-Rim; Bae, Yong-Soo

2012-01-01

The cytokine inducible SH2-domain protein (CISH) is a well-known STAT5 target gene, but its role in the immune system remains uncertain. In this study, we found that CISH is predominantly induced during dendritic cell (DC) development from mouse bone marrow (BM) cells and plays a crucial role in type 1 DC development and DC-mediated CTL activation. CISH knockdown reduced the expression of MHC class I, co-stimulatory molecules and pro-inflammatory cytokines in BMDCs. Meanwhile, the DC yield was markedly enhanced by CISH knockdown via cell-cycle activation and reduction of cell apoptosis. Down-regulation of cell proliferation at the later stage of DC development was found to be associated with CISH-mediated negative feedback regulation of STAT5 activation. In T-cell immunity, OT-1 T-cell proliferation was significantly reduced by CISH knockdown in DCs, whereas OT-2 T-cell proliferation was not affected by CISH knockdown. CTLs generated by DC vaccination were also markedly reduced by CISH knockdown, followed by significant impairment of DC-based tumor immunotherapy. Taken together, our data suggest that CISH expression at the later stage of DC development triggers the shutdown of DC progenitor cell proliferation and facilitates DC differentiation into a potent stimulator of CTLs. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Bidirectional Multi-Port DC-DC Converter Integrating Voltage Equalizer

DEFF Research Database (Denmark)

Chen, Jianfei; Hou, Shiying; Deng, Fujin

2015-01-01

A novel bidirectional multi-port dc-dc converter integrating voltage equalizer based on switched-capacitor voltage accumulator (SCVA) is proposed. It has two operating modes of charging and discharging for battery modules. All battery modules are connected in series indirectly and can be equalize...... battery modules with different voltages. Simulation results has shown the feasibility of the proposed converter.......A novel bidirectional multi-port dc-dc converter integrating voltage equalizer based on switched-capacitor voltage accumulator (SCVA) is proposed. It has two operating modes of charging and discharging for battery modules. All battery modules are connected in series indirectly and can be equalized...

A microgrid cluster structure and its autonomous coordination control strategy

DEFF Research Database (Denmark)

Zhou, Xiaoping; Zhou, Leming; Chen, Yandong

2018-01-01

This paper proposes a microgrid cluster structure and its autonomous coordination control strategy. Unlike existing microgrids that are purely AC or DC, the microgrid cluster studied here is an interconnected system with multiple AC and DC microgrids, which enables mutual power support among...... control method combining the normalized droop-based control and adaptive control is proposed for PEU, which can effectively realize mutual power support among microgrids and reduce the bus voltage or frequency deviation in microgrids. In addition, the adaptive control strategy of PEU can ensure...... that the bigger the normalized index of microgrid is, the larger the active power exchange coefficient is, which can make all of microgrids operate around the rated state as much as possible. Besides, EP is mainly used to balance the system power, and the hierarchical coordinated control method of EP is proposed...

A Current-Fed Isolated Bidirectional DC-DC Converter

DEFF Research Database (Denmark)

Sun, Xiaofeng; Wu, Xiaoying; Shen, Yanfeng

2017-01-01

This paper proposes a current-fed isolated bidirectional DC-DC converter (CF-IBDC) which has the advantages of wide input voltage range, low input current ripple, low conduction losses, and soft switching over the full operating range. Compared with conventional CF-IBDCs, the voltage spikes...

Bi-Directional DC-DC Converter for PHEV Applications

Energy Technology Data Exchange (ETDEWEB)

Abas Goodarzi

2011-01-31

Plug-In Hybrid Electric Vehicles (PHEV) require high power density energy storage system (ESS) for hybrid operation and high energy density ESS for Electric Vehicle (EV) mode range. However, ESS technologies to maximize power density and energy density simultaneously are not commercially feasible. The use of bi-directional DC-DC converter allows use of multiple energy storage, and the flexible DC-link voltages can enhance the system efficiency and reduce component sizing. This will improve fuel consumption, increase the EV mode range, reduce the total weight, reduce battery initial and life cycle cost, and provide flexibility in system design.

Determination of input/output characteristics of full-bridge AC/DC/DC converter for arc welding

OpenAIRE

Stefanov, Goce; Karadzinov, Ljupco; Sarac, Vasilija; Cingoski, Vlatko; Gelev, Saso

2016-01-01

This paper describes the design and practical implementation of AC/DC/DC converter in mode of arc welding. An analysis of the operation of AC/DC/DC converter and its input/output characteristics are determined with computer simulations. The practical part is consisted of AC/DC/DC converter prototype for arc welding with output power of 3 kW and switching frequency of 64 kHz. The operation of AC/DC/DC converter is validated with experimental measurements.

ITAR Free Commercial-of-the-Shelf DC/DC Converter

Science.gov (United States)

Denzinger, Wolfgang; Hintze, Thomas

2014-08-01

A commercial-of-the-shelf (COTS) DC/DC converter for digital space equipment has been developed by ASP under ESA contract with special emphasis on low cost, no use of ITAR listed EEE parts like Mosfets, minimum number of rad-hard digital IC's and a design tolerance against single event effects by appropriate filtering. However, the intention to qualify this discrete converter design for a low cost FM series production was difficult due to the high up-sceening cost of EEE-parts with one lot guarantee and minimum-by. To overcome this problem, in a next step a redesign of the DC/DC converter was performed with all semiconductors like bipolar transistors, rectifiers and zener diodes packaged into hybrids. With this approach it was possible to buy a high number of less expensive wafers or dies from one lot, to perform a lot acceptance test and to integrate the dies into hybrid packages with further up- screening for FM use. The semiconductors have been packaged into three signal hybrids with 44 pins and one power hybrid with 24 pins for the dissipating transistors and rectifiers. The design of the hybrids is such, that all integrated semiconductors can be tested individually. The qualification of four EQM DC/DC converters with different combinations of output voltages has been successfully performed and two FM's have been manufactured and tested.

Performance of 22.4-kW nonlaminated-frame dc series motor with chopper controller. [a dc to dc voltage converter

Science.gov (United States)

Schwab, J. R.

1979-01-01

Performance data obtained through experimental testing of a 22.4 kW traction motor using two types of excitation are presented. Ripple free dc from a motor-generator set for baseline data and pulse width modulated dc as supplied by a battery pack and chopper controller were used for excitation. For the same average values of input voltage and current, the motor power output was independent of the type of excitation. However, at the same speeds, the motor efficiency at low power output (corresponding to low duty cycle of the controller) was 5 to 10 percentage points lower on chopped dc than on ripple free dc. The chopped dc locked-rotor torque was approximately 1 to 3 percent greater than the ripple free dc torque for the same average current.

Characterising and modelling extended conducted electromagnetic interference in densely packed DC-DC converter

CSIR Research Space (South Africa)

Grobler, Inus

2013-09-01

Full Text Available . The military specified DC-DC converters are applicable, spanning from 100 W handheld power managers up to 2 kW DC-DC battery chargers. Circuit layout high frequency effects as well as high frequency impedances of the power components were characterised...

A New Sliding Mode Controller for DC/DC Converters in Photovoltaic Systems

Directory of Open Access Journals (Sweden)

M. Sarvi

2013-01-01

Full Text Available DC/DC converters are widely used in many industrial and electrical systems. As DC/DC converters are nonlinear and time-variant systems, the application of linear control techniques for the control of these converters is not suitable. In this paper, a new sliding mode controller is proposed as the indirect control method and compared to a simple direct control method in order to control a buck converter in photovoltaic applications. The solar arrays are dependent power sources with nonlinear voltage-current characteristics under different environmental conditions (insolation and temperature. From this point of view, the DC/DC converter is particularly suitable for the application of the sliding mode control in photovoltaic application, because of its controllable states. Simulations are performed in Matlab/Simulink software. The simulation results are presented for a step change in reference voltage and input voltage as well as step load variations. The simulations results of proposed method are compared with the conventional PID controller. The results show the good performance of the proposed sliding mode controller. The proposed method can be used for the other DC/DC converter.

Very High Frequency Half Bridge DC/DC Converter

DEFF Research Database (Denmark)

Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.

2014-01-01

This paper presents the first, off chip, class DE (resonant half bridge) converter working in the Very High Frequency (VHF) range. The benefits of using half bridge circuits both in the inverter and rectifier part of a VHF resonant dc/dc converter are analyzed and design equations for all...

Sheppard-Taylor Isolated High Boost DC-DC Converter

DEFF Research Database (Denmark)

Chub, Andrii; Siwakoti, Yam Prasad; Vinnikov, Dmitri

2017-01-01

This paper presents a new galvanically isolated step-up dc-dc converter intended for low-power but high step-up applications. The proposed converter is capable of regulating output voltage within a wide range of the input voltage or load variations. In contrast to competitors, the converter can...

A DC-DC Conversion Powering Scheme for the CMS Phase-1 Pixel Upgrade

CERN Document Server

Feld, Lutz Werner; Marcel Friedrichs; Richard Hensch; Karpinski, Waclaw; Klein, Katja; Sammet, Jan Domenik; Wlochal, Michael

2012-01-01

The powering scheme of the CMS pixel detector will be described, and the performance of prototype DC-DC buck converters will be presented, including power efficiency, system tests with DC-DC converters and pixel modules, thermal management, reliability at low temperature, and studies of potential frequency locking betwe...

Antiferromagnetic exchange coupling measurements on single Co clusters

Science.gov (United States)

Wernsdorfer, W.; Leroy, D.; Portemont, C.; Brenac, A.; Morel, R.; Notin, L.; Mailly, D.

2009-03-01

We report on single-cluster measurements of the angular dependence of the low-temperature ferromagnetic core magnetization switching field in exchange-coupled Co/CoO core-shell clusters (4 nm) using a micro-bridge DC superconducting quantum interference device (μ-SQUID). It is observed that the coupling with the antiferromagnetic shell induces modification in the switching field for clusters with intrinsic uniaxial anisotropy depending on the direction of the magnetic field applied during the cooling. Using a modified Stoner-Wohlfarth model, it is shown that the core interacts with two weakly coupled and asymmetrical antiferromagnetic sublattices. Ref.: C. Portemont, R. Morel, W. Wernsdorfer, D. Mailly, A. Brenac, and L. Notin, Phys. Rev. B 78, 144415 (2008)

Study on the Control Algorithm of Two-Stage DC-DC Converter for Electric Vehicles

Directory of Open Access Journals (Sweden)

Changhao Piao

2014-01-01

Full Text Available The fast response, high efficiency, and good reliability are very important characteristics to electric vehicles (EVs dc/dc converters. Two-stage dc-dc converter is a kind of dc-dc topologies that can offer those characteristics to EVs. Presently, nonlinear control is an active area of research in the field of the control algorithm of dc-dc converters. However, very few papers research on two-stage converter for EVs. In this paper, a fixed switching frequency sliding mode (FSFSM controller and double-integral sliding mode (DISM controller for two-stage dc-dc converter are proposed. And a conventional linear control (lag is chosen as the comparison. The performances of the proposed FSFSM controller are compared with those obtained by the lag controller. In consequence, the satisfactory simulation and experiment results show that the FSFSM controller is capable of offering good large-signal operations with fast dynamical responses to the converter. At last, some other simulation results are presented to prove that the DISM controller is a promising method for the converter to eliminate the steady-state error.

Regulation of DC development and DC-mediated T-cell immunity via CISH

OpenAIRE

Miah, Mohammad Alam; Bae, Yong-Soo

2013-01-01

Cytokine inducible SH2-containing protein (CISH) plays a crucial role in type 1 dendritic cell (DC) development as well as in the DC-mediated activation of cytotoxic T lymphocytes (CTLs). CISH expression at late DC developmental stages shuts down the proliferation of DC progenitors by negatively regulating signal transducer and activator of transcription 5 (STAT5) and facilitates the differentiation of DCs into potent stimulators of CTLs.

Regulation of DC development and DC-mediated T-cell immunity via CISH.

Science.gov (United States)

Miah, Mohammad Alam; Bae, Yong-Soo

2013-03-01

Cytokine inducible SH2-containing protein (CISH) plays a crucial role in type 1 dendritic cell (DC) development as well as in the DC-mediated activation of cytotoxic T lymphocytes (CTLs). CISH expression at late DC developmental stages shuts down the proliferation of DC progenitors by negatively regulating signal transducer and activator of transcription 5 (STAT5) and facilitates the differentiation of DCs into potent stimulators of CTLs.

Controlling DC-DC converters by chaos-based pulse width modulation to reduce EMI

International Nuclear Information System (INIS)

Li Hong; Zhang Bo; Li Zhong; Halang, Wolfgang A.; Chen Guanrong

2009-01-01

In this paper, periodic and chaotic behaviors of DC-DC converters under certain parametric conditions are simulated, experimentally verified, and analyzed. Motivated by the work of J.H.B. Deane and D.C. Hamill in 1996, where chaotic phenomena are useful in suppressing electromagnetic interference (EMI) by adjusting the parameters of the DC-DC converter and making it operate in chaos, a chaos-based pulse width modulation (CPWM) is proposed to distribute the harmonics of the DC-DC converters continuously and evenly over a wide frequency range, thereby reducing the EMI. The output waves and spectral properties of the EMI are simulated and analyzed as the carrier frequency or amplitude changes with regard to different chaotic maps. Simulation and experimental results are given to illustrate the effectiveness of the proposed CPWM, which provides a good example of applying chaos theory in engineering practice.

In vitro propagation of lnula royleana DC

Directory of Open Access Journals (Sweden)

Anna Stojakowska

2011-01-01

Full Text Available A micropropagation method, through axillary shoot proliferation, was elaborated for Inula royleana DC. (Asteraceae, a medicinal plant native of Himalaya. Primary explants (cotyledonary node explants and secondary explants (node explants of in vitro regenerated shoots of the plant, inoculated on MS medium supplemented with 0.1 μM NAA and 5.0 μM kinetin, regenerated 3.4 ± 1.2 and 5.1 ± 1.9 axillary shoots per explant, respectively. The regenerated shoots were easily rooting and adapting to growth in soil.

Human major histocompatibility complex contains a minimum of 19 genes between the complement cluster and HLA-B

International Nuclear Information System (INIS)

Spies, T.; Bresnahan, M.; Strominger, J.L.

1989-01-01

A 600-kilobase (kb) DNA segment from the human major histocompatibility complex (MHC) class III region was isolated by extension of a previous 435-kb chromosome walk. The contiguous series of cloned overlapping cosmids contains the entire 555-kb interval between C2 in the complement gene cluster and HLA-B. This region is known to encode the tumor necrosis factors (TNFs) α and β, B144, and the major heat shock protein HSP70. Moreover, a cluster of genes, BAT1-BAT5 (HLA-B-associated transcripts) have been localized in the vicinity of the genes for TNFα and TNFβ. An additional four genes were identified by isolation of corresponding cDNA clones with cosmid DNA probes. These genes for BAT6-BAT9 were mapped near the gene for C2 within a 120-kb region that includes a HSP70 gene pair. These results, together with complementary data from a similar recent study, indicated the presence of a minimum of 19 genes within the C2-HLA-B interval of the MHC class III region. Although the functional properties of most of these genes are yet unknown, they may be involved in some aspects of immunity. This idea is supported by the genetic mapping of the hematopoietic histocompatibility locus-1 (Hh-1) in recombinant mice between TNFα and H-2S, which is homologous to the complement gene cluster in humans

Leaf, stem bark and fruit anatomy of zanthoxylum armatum dc. (rutaceae)

International Nuclear Information System (INIS)

Barkatullah, A.; Ibrar, M.; Jelani, G.; Ahmad, I.

2014-01-01

Zanthoxylum armatum DC. (Rutaceae) is an important medicinal plant. The present study deals with anatomical exploration of the leaf, stem bark and fruit of this plant. Leaf of Z. armatum is bifacial, compound and punctate with glabrous surfaces having a single layer of epidermis and palisade mesophyll. The leaf has a Palisade ratio ranged from 6.00 to 9.00 (8.2 +- 0.32). Vein islets and vein termination number were 14-21 (16.8 +- 0.64) and 17-21 (19.1 +- 0.43) per mm2 respectively. The vein-islets were quite distinct with squaresh, elongated, polygonal or irregular in shape bounding many forked and unforked vascular branches. Adaxial surface of Z. armatum leaf midrib was planoconvex while the abaxial surface was semicircular in appearance. The diagnostic feature of the leaf was the complete absence of any kind of trichomes or any other appendages. The leaf showed prominent oil cavities. Nine types of stomata with different frequencies and other dimensions were observed. Brachparatetracytic stomata was the most frequent stoma (80%) followed by actinostephanocytic (40%) and then straucytic and brachyparacytic (30%) each. Hemiparacytic and stomatal cluster were the rarely occurring stomata (10% each) present on the lower epidermis of the leaf. Stomatal cluster, which is considered to be a special leaf epidermal feature and reported only in few genera of vascular plants, was also recorded in this plant. Bark and fruit anatomy of Z. armatum showed different tissue arrangement. The seed was non endospermic and contains an elongated embryo. The present study will be helpful in the phylogeny and taxonomic description of this important medicinal plant. (author)

Effect of D.C. electric field on salt bath nitriding for 35 steel and kinetics analysis

International Nuclear Information System (INIS)

Zhou, Zhengshou; Dai, Mingyang; Shen, Zhiyuan; Hu, Jing

2015-01-01

Highlights: • A rapid salt bath nitriding technology enhanced by D.C. electric field was developed primarily. • The heating duration could be shortened to less than a half. • Higher surface hardness, modestly higher sub-surface hardness and superior hardness profile were obtained. • The diffusion coefficient of nitrogen was increased to more than 1.9 times and Q value was decrease. • Chemical reactions were promoted and active atoms were forced to diffuse directionally toward the treated specimen. - Abstract: A rapid salt bath nitriding technology was primarily developed by additionally applying direct current (D.C.) electric field on the basis of traditional technique (NM). Characterization of the modified surface layers was made by means of optical microscopy, Vickers micro-hardness test and X-ray diffraction analysis. The results showed that D.C. electric field could significantly enhance the nitriding efficiency and the enhancement effect was closely related to the intensity of D.C. electric field. By applying D.C electric field of 7.5 V, even a little thicker compound layer could be obtained at only half duration of that in traditional technique, and the thickness of compound layer increased more than 60%, from 18 μm up to 29 μm at the same treating temperature of 848 K and holding duration of 100 min. Meanwhile, higher surface hardness, modestly higher sub-surface hardness and superior hardness profile were obtained assisted by D.C. electric field. It was also found that the diffusion coefficient of nitrogen was increased more than 1.9 times and activation energy was decreased from 184 kJ/mol to 159 kJ/mol enhanced by D.C. electric field. The possible enhancement mechanism is that D.C. electric field can promote chemical reactions and produce more active nitrogen atoms in the salt bath, positively charge the active atoms and force them diffuse directionally toward the surface of the treated specimen, and hence significantly improve the efficiency

Elimination of output voltage oscillations in DC-DC converter using PWM with PI controller

Directory of Open Access Journals (Sweden)

Sreenivasappa Veeranna Bhupasandra

2010-01-01

Full Text Available In this paper the SIMULINK model of a PWM controlled DC-DC converter is modeled using switching function concept to control the speed of the DC motor. The presence of the voltage oscillation cycles due to higher switching frequency in the DC-DC converter is identified. The effect of these oscillations on the output voltage of the converter, Armature current, Developed torque and Speed of the DC motor is analyzed. In order to minimize the oscillation cycles the PI controller is proposed in the PWM controller.

Analysis of high voltage step-up nonisolated DC-DC boost converters

Science.gov (United States)

Alisson Alencar Freitas, Antônio; Lessa Tofoli, Fernando; Junior, Edilson Mineiro Sá; Daher, Sergio; Antunes, Fernando Luiz Marcelo

2016-05-01

A high voltage step-up nonisolated DC-DC converter based on coupled inductors suitable to photovoltaic (PV) systems applications is proposed in this paper. Considering that numerous approaches exist to extend the voltage conversion ratio of DC-DC converters that do not use transformers, a detailed comparison is also presented among the proposed converter and other popular topologies such as the conventional boost converter and the quadratic boost converter. The qualitative analysis of the coupled-inductor-based topology is developed so that a design procedure can be obtained, from which an experimental prototype is implemented to validate the theoretical assumptions.

Common mode noise in three-level DC-DC converters

CSIR Research Space (South Africa)

Grobler, Inus

2009-09-01

Full Text Available that three-level buck DC-DC converters in general generate much lower common mode currents than conventional two-level buck converters. Further, reductions in common mode currents are achieved by using the improved three-level topologies that have been...

Analysis and Design of Bi-Directional DC-DC Converter in the Extended Run Time DC UPS System Based on Fuel Cell and Supercapacitor

DEFF Research Database (Denmark)

Zhang, Zhe; Thomsen, Ole Cornelius; Andersen, Michael A. E.

2009-01-01

Abstract-In this paper, an extended run time DC UPS system structure with fuel cell and supercapacitor is investigated. A wide input range bi-directional dc-dc converter is described along with the phase-shift modulation scheme and phase-shift with duty cycle control, in different modes. The deli......Abstract-In this paper, an extended run time DC UPS system structure with fuel cell and supercapacitor is investigated. A wide input range bi-directional dc-dc converter is described along with the phase-shift modulation scheme and phase-shift with duty cycle control, in different modes...

DC-DC power converter research for Orbiter/Station power exchange

Science.gov (United States)

Ehsani, M.

1993-01-01

This project was to produce innovative DC-DC power converter concepts which are appropriate for the power exchange between the Orbiter and the Space Station Freedom (SSF). The new converters must interface three regulated power buses on SSF, which are at different voltages, with three fuel cell power buses on the Orbiter which can be at different voltages and should be tracked independently. Power exchange is to be bi-directional between the SSF and the Orbiter. The new converters must satisfy the above operational requirements with better weight, volume, efficiency, and reliability than is available from the present conventional technology. Two families of zero current DC-DC converters were developed and successfully adapted to this application. Most of the converters developed are new and are presented.

Sliding-mode control of single input multiple output DC-DC converter

Science.gov (United States)

Zhang, Libo; Sun, Yihan; Luo, Tiejian; Wan, Qiyang

2016-10-01

Various voltage levels are required in the vehicle mounted power system. A conventional solution is to utilize an independent multiple output DC-DC converter whose cost is high and control scheme is complicated. In this paper, we design a novel SIMO DC-DC converter with sliding mode controller. The proposed converter can boost the voltage of a low-voltage input power source to a controllable high-voltage DC bus and middle-voltage output terminals, which endow the converter with characteristics of simple structure, low cost, and convenient control. In addition, the sliding mode control (SMC) technique applied in our converter can enhance the performances of a certain SIMO DC-DC converter topology. The high-voltage DC bus can be regarded as the main power source to the high-voltage facility of the vehicle mounted power system, and the middle-voltage output terminals can supply power to the low-voltage equipment on an automobile. In the respect of control algorithm, it is the first time to propose the SMC-PID (Proportion Integration Differentiation) control algorithm, in which the SMC algorithm is utilized and the PID control is attended to the conventional SMC algorithm. The PID control increases the dynamic ability of the SMC algorithm by establishing the corresponding SMC surface and introducing the attached integral of voltage error, which endow the sliding-control system with excellent dynamic performance. At last, we established the MATLAB/SIMULINK simulation model, tested performance of the system, and built the hardware prototype based on Digital Signal Processor (DSP). Results show that the sliding mode control is able to track a required trajectory, which has robustness against the uncertainties and disturbances.

Genetic Diversity of the fliC Genes Encoding the Flagellar Antigen H19 of Escherichia coli and Application to the Specific Identification of Enterohemorrhagic E. coli O121:H19

Science.gov (United States)

Beutin, Lothar; Delannoy, Sabine

2015-01-01

Enterohemorrhagic Escherichia coli (EHEC) O121:H19 belong to a specific clonal type distinct from other classical EHEC and major enteropathogenic E. coli groups and is regarded as one of the major EHEC serogroups involved in severe infections in humans. Sequencing of the fliC genes associated with the flagellar antigen H19 (fliCH19) revealed the genetic diversity of the fliCH19 gene sequences in E. coli. A cluster analysis of 12 fliCH19 sequences, 4 from O121 and 8 from non-O121 E. coli strains, revealed five different genotypes. All O121:H19 strains fell into one cluster, whereas a second cluster was formed by five non-O121:H19 strains. Cluster 1 and cluster 2 strains differ by 27 single nucleotide exchanges in their fliCH19 genes (98.5% homology). Based on allele discrimination of the fliCH19 genes, a real-time PCR test was designed for specific identification of EHEC O121:H19. The O121 fliCH19 PCR tested negative in 73 E. coli H19 strains that belonged to serogroups other than O121, including 28 different O groups, O-nontypeable H19, and O-rough:H19 strains. The O121 fliCH19 PCR reacted with all 16 tested O121:H19 strains and 1 O-rough:H19 strain which was positive for the O121 wzx gene. A cross-reaction was observed only with E. coli H32 strains which share sequence similarities in the target region of the O121 fliCH19 PCR. The combined use of O-antigen genotyping (O121 wzx) and the detection of O121 fliCH19 allele type contributes to improving the identification and molecular serotyping of EHEC O121:H19 motile and nonmotile strains and variants of these strains lacking stx genes. PMID:25862232

Y-Source Boost DC/DC Converter for Distributed Generation

DEFF Research Database (Denmark)

Siwakoti, Yam P.; Loh, Poh Chiang; Blaabjerg, Frede

2015-01-01

This paper introduces a versatile Y-source boost dc/dc converter intended for distributed power generation, where high gain is often demanded. The proposed converter uses a Y-source impedance network realized with a tightly coupled three-winding inductor for high voltage boosting that is presently...

SUBCONTRACT REPORT: DC-DC Converter for Fuel Cell and Hybrid Vehicles

Energy Technology Data Exchange (ETDEWEB)

Marlino, Laura D [ORNL; Zhu, Lizhi [Ballard Power Systems/Siemens VDO

2007-07-01

The goal of this project is to develop and fabricate a 5kW dc-dc converter with a baseline 14V output capability for fuel cell and hybrid vehicles. The major objectives for this dc-dc converter technology are to meet: Higher efficiency (92%); High coolant temperature,e capability (105 C); High reliability (15 Years/150,000miles); Smaller volume (5L); Lower weight (6kg); and Lower cost ($75/kW). The key technical challenge for these converters is the 105 C coolant temperatures. The power switches and magnetics must be designed to sustain these operating temperatures reliably, without a large cost/mass/volume penalty.

Multi-level cascaded DC/DC converters for PV applications

Directory of Open Access Journals (Sweden)

Ahmed A.A. Hafez

2015-12-01

Full Text Available A robust multi-level cascaded DC/DC system for Photovoltaic (PV application is advised in this article. There are three PV generators, each is coupled to a half-bridge buck cell. Each PV-generator–buck-converter channel is controlled such that maximum power is captured independently under different irradiation and temperature levels. The system operation under normal and abnormal conditions was comprehensively investigated. Internal Model Control (IMC technique was adopted for tuning the controllers. An elaborate switching modulation strategy was used to reduce the current ripple and inductor size, while maintaining high efficiency. Annotative, simple and robust remedial strategies were proposed to mitigate different anticipated faults. Comprehensive simulation results in Matlab environment were illustrated for corroborating the performance of the advised cascaded DC/DC system under normal/abnormal conditions. The proposed system enjoys the merits of independency, reduced volumetric dimensions and improved efficiency. Furthermore, the system is inherently fault-tolerant.

Development of a DC-DC conversion powering scheme for the CMS Phase-1 pixel upgrade

CERN Document Server

Feld, Lutz Werner; Karpinski, Waclaw; Klein, Katja; Lipinski, Martin; Preuten, Marius; Max Rauch; Rittich, David Michael; Sammet, Jan Domenik; Wlochal, Michael

2014-01-01

A novel powering scheme based on the DC-DC conversion technique will be exploited to power the CMS Phase-1 pixel detector. DC-DC buck converters for the CMS pixel project have been developed, based on the AMIS5 ASIC designed by CERN. The powering system of the Phase-1 pixel detector is described and the performance of the converter prototypes is detailed, including power efficiency, stability of the output voltage, shielding, and thermal management. Results from a test of the magnetic field tolerance of the DC-DC converters are reported. System tests with pixel modules using many components of the future pixel barrel system are summarized. Finally first impressions from a pre-series of 200 DC-DC converters are presented.

Auxiliary resonant DC tank converter

Science.gov (United States)

Peng, Fang Z.

2000-01-01

An auxiliary resonant dc tank (ARDCT) converter is provided for achieving soft-switching in a power converter. An ARDCT circuit is coupled directly across a dc bus to the inverter to generate a resonant dc bus voltage, including upper and lower resonant capacitors connected in series as a resonant leg, first and second dc tank capacitors connected in series as a tank leg, and an auxiliary resonant circuit comprising a series combination of a resonant inductor and a pair of auxiliary switching devices. The ARDCT circuit further includes first clamping means for holding the resonant dc bus voltage to the dc tank voltage of the tank leg, and second clamping means for clamping the resonant dc bus voltage to zero during a resonant period. The ARDCT circuit resonantly brings the dc bus voltage to zero in order to provide a zero-voltage switching opportunity for the inverter, then quickly rebounds the dc bus voltage back to the dc tank voltage after the inverter changes state. The auxiliary switching devices are turned on and off under zero-current conditions. The ARDCT circuit only absorbs ripples of the inverter dc bus current, thus having less current stress. In addition, since the ARDCT circuit is coupled in parallel with the dc power supply and the inverter for merely assisting soft-switching of the inverter without participating in real dc power transmission and power conversion, malfunction and failure of the tank circuit will not affect the functional operation of the inverter; thus a highly reliable converter system is expected.

Dc-To-Dc Converter Uses Reverse Conduction Of MOSFET's

Science.gov (United States)

Gruber, Robert P.; Gott, Robert W.

1991-01-01

In modified high-power, phase-controlled, full-bridge, pulse-width-modulated dc-to-dc converters, switching devices power metal oxide/semiconductor field-effect transistors (MOSFET's). Decreases dissipation of power during switching by eliminating approximately 0.7-V forward voltage drop in anti-parallel diodes. Energy-conversion efficiency increased.

Development of a green mode DC/DC converter available to portable nuclear instrument

International Nuclear Information System (INIS)

Gao Feiyan; Wu Longxiong; Tan Wei; Tang Yaogeng

2010-01-01

A green mode DC/DC converter was developed which suitable to the portable nuclear instrument which is powered by battery and is sometime at stand-by mode. Some updated control approaches such as pseudo-resonant type power supply control and synchronous rectification were adopted to makethe DC/DC converter operate with low power consumption and high efficiency. The test results the battery can be prolonged with this converter. (authors)

A SPECTROSCOPIC ANALYSIS OF THE GALACTIC GLOBULAR CLUSTER NGC 6273 (M19)

Energy Technology Data Exchange (ETDEWEB)

Johnson, Christian I.; Caldwell, Nelson [Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, MS-15, Cambridge, MA 02138 (United States); Rich, R. Michael [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States); Pilachowski, Catherine A. [Astronomy Department, Indiana University Bloomington, Swain West 319, 727 East 3rd Street, Bloomington, IN 47405-7105 (United States); Mateo, Mario; Bailey, John I. III [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Crane, Jeffrey D., E-mail: cjohnson@cfa.harvard.edu, E-mail: ncaldwell@cfa.harvard.edu, E-mail: rmr@astro.ucla.edu, E-mail: catyp@astro.indiana.edu, E-mail: mmateo@umich.edu, E-mail: baileyji@umich.edu, E-mail: crane@obs.carnegiescience.edu [The Observatories of the Carnegie Institution for Science, Pasadena, CA 91101 (United States)

2015-08-15

A combined effort utilizing spectroscopy and photometry has revealed the existence of a new globular cluster class. These “anomalous” clusters, which we refer to as “iron-complex” clusters, are differentiated from normal clusters by exhibiting large (≳0.10 dex) intrinsic metallicity dispersions, complex sub-giant branches, and correlated [Fe/H] and s-process enhancements. In order to further investigate this phenomenon, we have measured radial velocities and chemical abundances for red giant branch stars in the massive, but scarcely studied, globular cluster NGC 6273. The velocities and abundances were determined using high resolution (R ∼ 27,000) spectra obtained with the Michigan/Magellan Fiber System (M2FS) and MSpec spectrograph on the Magellan–Clay 6.5 m telescope at Las Campanas Observatory. We find that NGC 6273 has an average heliocentric radial velocity of +144.49 km s{sup −1} (σ = 9.64 km s{sup −1}) and an extended metallicity distribution ([Fe/H] = −1.80 to −1.30) composed of at least two distinct stellar populations. Although the two dominant populations have similar [Na/Fe], [Al/Fe], and [α/Fe] abundance patterns, the more metal-rich stars exhibit significant [La/Fe] enhancements. The [La/Eu] data indicate that the increase in [La/Fe] is due to almost pure s-process enrichment. A third more metal-rich population with low [X/Fe] ratios may also be present. Therefore, NGC 6273 joins clusters such as ω Centauri, M2, M22, and NGC 5286 as a new class of iron-complex clusters exhibiting complicated star formation histories.

SPEED CONTROL OF DC MOTOR ON LOAD USING FUZZY LOGIC ...

African Journals Online (AJOL)

This paper presents the development of a fuzzy logic controller for the driver DC motor in the lube oil system of the H25 Hitachi gas turbine generator. The turbine generator is required to run at an operating pressure of 1.5bar with the low and the high pressure trip points being 0.78 bar and 1.9 bar respectively. However, the ...

A Dual-Buck–Boost AC/DC Converter for DC Nanogrid With Three Terminal Outputs

DEFF Research Database (Denmark)

Wu, Weimin; Wang, Houqing; Liu, Yuan

2017-01-01

Due to the widely used dc characterized loads and more distributed power generation sources, the dc nanogrid becomes more and more popular, and it is seen as an alternative to the ac grid. For safety considerations, the dc nanogrid should provide reliable grounding for the residential loads...... such as the low-voltage ac power system. There are three typical grounding configurations for a dc nanogrid: the united grounding, the unidirectional grounding, and the virtual isolated grounding. Each grounding configuration has its own specifications to ac/dc converters. In this paper, a dual-buck-boost ac/dc...... converter for use in the united-grounding-configuration-based dc nanogrid with three terminal outputs is proposed. The working principle of this converter is presented in detail through analyzing the equivalent circuits. Experiments are carried out to verify the theoretical analysis....

DESIGN OPTIMIZATION OF RESONANT DC-DC CONVERTERS

OpenAIRE

Belqasem Aljafari

2016-01-01

Resonant DC/DC converters are the class of converters, which have L-C resonant tank serving as a major part of the power conversion process. The fundamental concept of the resonant converter is that the circulating energy in an L-C resonant circuit is manageable by changing the operating frequency, and therefore the converter can condition the input power to the desired output voltage. The development in power conversion technology is steady demand for high power efficiency and high power den...

High Voltage Coil Current Sensor for DC-DC Converters Employing DDCC

Directory of Open Access Journals (Sweden)

M. Drinovsky

2015-12-01

Full Text Available Current sensor is an integral part of every switching converter. It is used for over-current protection, regulation and in case of multiphase converters for balancing. A new high voltage current sensor for coil-based current sensing in DC-DC converters is presented. The sensor employs DDCC with high voltage input stage and gain trimming. The circuit has been simulated and implemented in 0.35 um BCD technology as part of a multiphase DC-DC converter where its function has been verified. The circuit is able to sustain common mode voltage on the input up to 40 V, it occupies 0.387*0.345 mm2 and consumes 3.2 mW typically.

On the modelling of linear-assisted DC-DC voltage regulators for photovoltaic solar energy systems

Science.gov (United States)

Martínez-García, Herminio; García-Vílchez, Encarna

2017-11-01

This paper shows the modelling of linear-assisted or hybrid (linear & switching) DC/DC voltage regulators. In this kind of regulators, an auxiliary linear regulator is used, which objective is to cancel the ripple at the output voltage and provide fast responses for load variations. On the other hand, a switching DC/DC converter, connected in parallel with the linear regulator, allows to supply almost the whole output current demanded by the load. The objective of this topology is to take advantage of the suitable regulation characteristics that series linear voltage regulators have, but almost achieving the high efficiency that switching DC/DC converters provide. Linear-assisted DC/DC regulators are feedback systems with potential instability. Therefore, their modelling is mandatory in order to obtain design guidelines and assure stability of the implemented power supply system.

A Feedback Passivation Design for DC Microgrid and Its DC/DC Converters

Directory of Open Access Journals (Sweden)

Feifan Ji

2016-12-01

Full Text Available There are difficulties in analyzing the stability of microgrids since they are located on various network structures. However, considering that the network often consists of passive elements, the passivity theory is applied in this paper to solve the above-mentioned problem. It has been formerly shown that when the network is weakly strictly positive real (WSPR, the DC microgrid is stable if all interfaces between the microgrid and converters are made to be passive, which is called interface passivity. Then, the feedback passivation method is proposed for the controller design of various DC–DC converters to achieve the interface passivity. The interface passivity is different from the passivity of closed-loop systems on which the passivity based control (PBC concentrates. The feedback passivation design is detailed for typical buck converters and boost converters in terms of conditions that the controller parameters should satisfy. The theoretical results are verified by a hardware-in-loop real-time labotray (RTLab simulation of a DC microgrid with four generators.

Test Results of Selected Commercial DC/DC Converters under Cryogenic Temperatures - A Digest

Science.gov (United States)

Patterson, Richard; Hammoud, Ahmad

2010-01-01

DC/DC converters are widely used in space power systems in the areas of power management and distribution, signal conditioning, and motor control. Design of DC/DC converters to survive cryogenic temperatures will improve the power system performance, simplify design, and reduce development and launch costs. In this work, the performance of nine COTS modular, low-tomedium power DC/DC converters was investigated under cryogenic temperatures. The converters were evaluated in terms of their output regulation, efficiency, and input and output currents. At a given temperature, these properties were obtained at various input voltages and at different load levels. A summary on the performance of the tested converters was given. More comprehensive testing and in-depth analysis of performance under long-term exposure to extreme temperatures are deemed necessary to establish the suitability of these and other devices for use in the harsh environment of space exploration missions.

A Bidirectional Resonant DC-DC Converter Suitable for Wide Voltage Gain Range

DEFF Research Database (Denmark)

Shen, Yanfeng; Wang, Huai; Al-Durra, Ahmed

2018-01-01

This paper proposes a new bidirectional resonant dc-dc converter suitable for wide voltage gain range applications (e.g., energy storage systems). The proposed converter overcomes the narrow voltage gain range of conventional resonant dc-dc converters, and meanwhile achieves high efficiency...... losses. The operation principles and characteristics of the proposed converter are firstly analyzed in this paper. Then the analytical solutions for the voltage gain, soft-switching, and rms currents are derived, which facilitates the parameters design and optimization. Finally, the proposed topology...... and analysis are verified with experimental results obtained from a 1-kW converter prototype....

Y-source impedance-network-based isolated boost DC/DC converter

DEFF Research Database (Denmark)

Siwakoti, Yam P.; Town, Graham; Loh, Poh Chiang

2014-01-01

A dc-dc converter with very high voltage gain is proposed in this paper for any medium-power application requiring a high voltage boost with galvanic isolation. The proposed converter topology can be realized using only two switches. With this topology a very high voltage boost can be achieved even...... with a relatively low duty cycle of the switches, and the gain obtainable is presently not matched by any existing impedance network based converter operated at the same duty ratio. The proposed converter has a Y-source impedance network to boost the voltage at the intermediate dc-link side and a push......-pull transformer for square-wave AC inversion and isolation. The voltage-doubler rectifier provides a constant dc voltage at the output stage. A theoretical analysis of the converter is presented, supported by simulation and experimental results. A 250 W down-scaled prototype was implemented in the laboratory...

Multilevel DC link inverter

Science.gov (United States)

Su, Gui-Jia

2003-06-10

A multilevel DC link inverter and method for improving torque response and current regulation in permanent magnet motors and switched reluctance motors having a low inductance includes a plurality of voltage controlled cells connected in series for applying a resulting dc voltage comprised of one or more incremental dc voltages. The cells are provided with switches for increasing the resulting applied dc voltage as speed and back EMF increase, while limiting the voltage that is applied to the commutation switches to perform PWM or dc voltage stepping functions, so as to limit current ripple in the stator windings below an acceptable level, typically 5%. Several embodiments are disclosed including inverters using IGBT's, inverters using thyristors. All of the inverters are operable in both motoring and regenerating modes.

Stability analysis of a high-step-Up DC grid-connected two-stage boost DC-DC converter

Directory of Open Access Journals (Sweden)

El Aroudi A.

2014-01-01

Full Text Available High conversion ratio switching converters are used whenever there is a need to step-up dc source voltage level to a much higher output dc voltage level such as in photovoltaic systems, telecommunications and in some medical applications. A simple solution for achieving this high conversion ratio is by cascading different stages of dc-dc boost converters. The individual converters in such a cascaded system are usually designed separately applying classical design criteria. However these criteria may not be applicable for the complete cascaded system . This paper first presents a glimpse on the bifurcation behavior that a cascade connection of two boost converters can exhibit. It is shown that the desired periodic orbit can undergo period doubling leading to subharmonic oscillations and chaotic regimes. Then, in order to simplify the analysis the second stage is considered as constant current sink and design-oriented analysis is carried out to obtain stability boundaries in the parameter space by taking into account slope interactions between the state variables in the two-different stages.

The anterior hypothalamus in cluster headache.

Science.gov (United States)

Arkink, Enrico B; Schmitz, Nicole; Schoonman, Guus G; van Vliet, Jorine A; Haan, Joost; van Buchem, Mark A; Ferrari, Michel D; Kruit, Mark C

2017-10-01

Objective To evaluate the presence, localization, and specificity of structural hypothalamic and whole brain changes in cluster headache and chronic paroxysmal hemicrania (CPH). Methods We compared T1-weighted magnetic resonance images of subjects with cluster headache (episodic n = 24; chronic n = 23; probable n = 14), CPH ( n = 9), migraine (with aura n = 14; without aura n = 19), and no headache ( n = 48). We applied whole brain voxel-based morphometry (VBM) using two complementary methods to analyze structural changes in the hypothalamus: region-of-interest analyses in whole brain VBM, and manual segmentation of the hypothalamus to calculate volumes. We used both conservative VBM thresholds, correcting for multiple comparisons, and less conservative thresholds for exploratory purposes. Results Using region-of-interest VBM analyses mirrored to the headache side, we found enlargement ( p cluster headache compared to controls, and in all participants with episodic or chronic cluster headache taken together compared to migraineurs. After manual segmentation, hypothalamic volume (mean±SD) was larger ( p cluster headache compared to controls (1.72 ± 0.15 ml) and migraineurs (1.68 ± 0.19 ml). Similar but non-significant trends were observed for participants with probable cluster headache (1.82 ± 0.19 ml; p = 0.07) and CPH (1.79 ± 0.20 ml; p = 0.15). Increased hypothalamic volume was primarily explained by bilateral enlargement of the anterior hypothalamus. Exploratory whole brain VBM analyses showed widespread changes in pain-modulating areas in all subjects with headache. Interpretation The anterior hypothalamus is enlarged in episodic and chronic cluster headache and possibly also in probable cluster headache or CPH, but not in migraine.

Digitally intensive DC-DC converter for extreme space environments, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — The Space Micro-Arizona State University (ASU) team will develop an all-digitally controlled, wide temperature range point-of-load switch-mode DC-DC regulator core...

Zero-voltage DC/DC converter with asymmetric pulse-width modulation for DC micro-grid system

Science.gov (United States)

Lin, Bor-Ren

2018-04-01

This paper presents a zero-voltage switching DC/DC converter for DC micro-grid system applications. The proposed circuit includes three half-bridge circuit cells connected in primary-series and secondary-parallel in order to lessen the voltage rating of power switches and current rating of rectifier diodes. Thus, low voltage stress of power MOSFETs can be adopted for high-voltage input applications with high switching frequency operation. In order to achieve low switching losses and high circuit efficiency, asymmetric pulse-width modulation is used to turn on power switches at zero voltage. Flying capacitors are used between each circuit cell to automatically balance input split voltages. Therefore, the voltage stress of each power switch is limited at Vin/3. Finally, a prototype is constructed and experiments are provided to demonstrate the circuit performance.

A Fixed-Frequency Bidirectional Resonant DC-DC Converter Suitable for Wide Voltage Gain Range

DEFF Research Database (Denmark)

Shen, Yanfeng; Wang, Huai; Blaabjerg, Frede

2017-01-01

This paper proposes a new bidirectional resonant dc-dc converter suitable for wide voltage gain range applications (e.g., energy storage systems). The proposed converter overcomes the narrow voltage gain range of conventional resonant DC-DC converters, and meanwhile achieves high efficiency...... and characteristics of the proposed converter are analyzed. Finally, a 1-kW converter prototype is built and the experimental results verify the theoretical analyses....

Pulse-width modulated DC-DC power converters

CERN Document Server

Kazimierczuk, Marian K

2008-01-01

This book studies switch-mode power supplies (SMPS) in great detail. This type of converter changes an unregulated DC voltage into a high-frequency pulse-width modulated (PWM) voltage controlled by varying the duty cycle, then changes the PWM AC voltage to a regulated DC voltage at a high efficiency by rectification and filtering. Used to supply electronic circuits, this converter saves energy and space in the overall system. With concept-orientated explanations, this book offers state-of-the-art SMPS technology and promotes an understanding of the principle operations of PWM converters,

Digitally intensive DC-DC converter for extreme space environments, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The Space Micro –Arizona State University (ASU) team will develop an all-digitally controlled, wide temperature range point-of-load switch-mode DC-DC regulator core...

DC Voltage Droop Control Implementation in the AC/DC Power Flow Algorithm: Combinational Approach

DEFF Research Database (Denmark)

Akhter, F.; Macpherson, D.E.; Harrison, G.P.

2015-01-01

of operational flexibility, as more than one VSC station controls the DC link voltage of the MTDC system. This model enables the study of the effects of DC droop control on the power flows of the combined AC/DC system for steady state studies after VSC station outages or transient conditions without needing...... to use its complete dynamic model. Further, the proposed approach can be extended to include multiple AC and DC grids for combined AC/DC power flow analysis. The algorithm is implemented by modifying the MATPOWER based MATACDC program and the results shows that the algorithm works efficiently....

High-Voltage DC-DC Converter Topology for PV Energy Utilization - Investigation and Implementation

DEFF Research Database (Denmark)

Sanjeevikumar, Padmanaban; Blaabjerg, Frede; Wheeler, Patrick

2017-01-01

This paper exploited the utilization of photovoltaic (PV) energy system with high-voltage (HV) output DC-DC converter. Classical boost converters are used for both renewable energy integration and HV applications, but limited by reducing output/efficiency in performance. Moreover, as parasitic...... elements suppress the power transfer ratio, converter needs to maximize the PV energy utilization. This investigation study focused to include additional parasitic elements (voltage-lift technique) to a standard DC-DC buck converter and to overcome all the above drawbacks to maximize the PV power...

Computer Simulation of Phase Shifted Series Resonant DC to DC Converter

Directory of Open Access Journals (Sweden)

P. PARVATHY

2016-01-01

Full Text Available This paper deals with digital simulation of phase shifted series resonant DC to DC converter using Matlab Simulink. The Simulink models for open loop and closed loop systems are developed and they are used for simulation studies. This converter is capable of producing ripple free DC output. Switching losses and switching stresses are reduced by using soft switching. This converter has advantages like high power density and low switching losses. Theoretical predictions are well supported by the simulation results.

Equilibrium Structures and Absorption Spectra for SixOy Molecular Clusters using Density Functional Theory

Science.gov (United States)

2017-05-05

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--17-9724 Equilibrium Structures and Absorption Spectra for SixOy Molecular Clusters...TELEPHONE NUMBER (include area code) b. ABSTRACT c. THIS PAGE 18. NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Equilibrium Structures and Absorption...and electronic excited-state absorption spectra for eqilibrium structures of SixOy molecular clusters using density function theory (DFT) and time

Power flow analysis for DC voltage droop controlled DC microgrids

DEFF Research Database (Denmark)

Li, Chendan; Chaudhary, Sanjay; Dragicevic, Tomislav

2014-01-01

This paper proposes a new algorithm for power flow analysis in droop controlled DC microgrids. By considering the droop control in the power flow analysis for the DC microgrid, when compared with traditional methods, more accurate analysis results can be obtained. The algorithm verification is ca...

World's largest DC flywheel generator for the toroidal field power supply of JAERI's JFT-2M Tokamak nuclear fusion reactor

International Nuclear Information System (INIS)

Tani, Takashi; Nakanishi, Yuji; Horita, Tsuyoshi; Kawase, Chiharu; Oyabu, Isao; Kishimoto, Takeshi.

1996-01-01

Mitsubishi Electric has delivered the world's largest DC generator for the toroidal field coil power supply of the JFT-2M Tokamak at the Japan Atomic Energy Research Institute. The unit rotates at 225 or 460 rpm, providing a maximum rated output of 2,700 V, 19,000 A and 51.3 MW. The toroidal field is a DC field, so use of a DC generator permits a simpler design consuming less floor space than an AC drive system. The generator was manufactured following extensive studies on commutation, mechanical strength and insulation. (author)

Light weight, high power, high voltage dc/dc converter technologies

Science.gov (United States)

Kraus, Robert; Myers, Ira; Baumann, Eric

1990-01-01

Power-conditioning weight reductions by orders of magnitude will be required to enable the megawatt-power-level space systems envisioned by the Strategic Defense Initiative, the Air Force, and NASA. An interagency program has been initiated to develop an 0.1-kg/kW dc/dc converter technology base for these future space applications. Three contractors are in the first phase of a competitive program to develop a megawatt dc/dc converter. Researchers at NASA Lewis Research Center are investigating innovative converter topology control. Three different converter subsystems based on square wave, resonant, and super-resonant topologies are being designed. The components required for the converter designs cover a wide array of technologies. Two different switches, one semiconductor and the other gas, are under development. Issues related to thermal management and material reliability for inductors, transformers, and capacitors are being investigated in order to maximize power density. A brief description of each of the concepts proposed to meet the goals of this program is presented.

Digital peak current mode control with adaptive slope compensation for DC-DC converters

DEFF Research Database (Denmark)

Andersen, Karsten Holm; Nymand, Morten

2017-01-01

performance and stability of current mode control. The presented method adapt to DC-DC converter operating conditions by estimating the rising and falling inductor current slopes, to apply a current slope compensation value to obtain a constant quality factor. The experimental results verifies the theoretical......This paper presents an adaptive slope compensation method for peak current mode control of digital controlled DC-DC converters, which controls the quality factor of the complex conjugated poles at half the switching frequency. Using quality factor control enables optimization of the dynamic...

DC-Link Compensation Method for Slim DC Link Drives Fed by Soft Grid

DEFF Research Database (Denmark)

Mathe, Laszlo; Rosendahl Andersen, Henrik; Lazar, Radu

2010-01-01

Slim DC-link PWM (AC) drives for lowperformance applications are emerging on the market. Such drives equipped with a small DC-link capacitance exhibit instability tendencies, if installed on a soft line, giving a degraded performance. The total harmonic distortion (THD) and the partially weighted...... harmonic distortion (PWHD) of the line current are degraded, if resonance between the line impedance and the DC-link capacitance occurs. Likewise, the motor performance is affected negatively giving extra torque ripple, vibration and acoustic-noise emission. This paper proposes a novel DC-link compensation...

High-power three-port three-phase bidirectional DC-DC converter

NARCIS (Netherlands)

Tao, H.; Duarte, J.L.; Hendrix, M.A.M.

2007-01-01

This paper proposes a three-port three-phase bidirectional dc-dc converter suitable for high-power applications. The converter combines a slow primary source and a fast storage to power a common load (e.g., an inverter). Since this type of system is gaining popularity in sustainable energy

Precharge strategies for isolated modular DC-DC converters under two different start-up conditions

DEFF Research Database (Denmark)

Zhang, Yi; Wang, Huai; Li, Binbin

2017-01-01

The isolated modular DC-DC converter (IMDCC) is a new topology designed to connect high-voltage direct current (HVDC) lines with different voltage levels, which ties two DC grids by using two modular multilevel converters (MMCs) via a medium-frequency transformer. Due to the large value of capaci......The isolated modular DC-DC converter (IMDCC) is a new topology designed to connect high-voltage direct current (HVDC) lines with different voltage levels, which ties two DC grids by using two modular multilevel converters (MMCs) via a medium-frequency transformer. Due to the large value...... of capacitance in the IMDCC, proper precharge strategies before the start-up are significant for the safety and reliability of the whole system. This paper presents two closed-loop precharge control strategies to fully charge the sub-module (SM) capacitors of the IMDCC, considering two different start...

Modeling and analysis of fractional order DC-DC converter.

Science.gov (United States)

Radwan, Ahmed G; Emira, Ahmed A; AbdelAty, Amr M; Azar, Ahmad Taher

2017-07-11

Due to the non-idealities of commercial inductors, the demand for a better model that accurately describe their dynamic response is elevated. So, the fractional order models of Buck, Boost and Buck-Boost DC-DC converters are presented in this paper. The detailed analysis is made for the two most common modes of converter operation: Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM). Closed form time domain expressions are derived for inductor currents, voltage gain, average current, conduction time and power efficiency where the effect of the fractional order inductor is found to be strongly present. For example, the peak inductor current at steady state increases with decreasing the inductor order. Advanced Design Systems (ADS) circuit simulations are used to verify the derived formulas, where the fractional order inductor is simulated using Valsa Constant Phase Element (CPE) approximation and Generalized Impedance Converter (GIC). Different simulation results are introduced with good matching to the theoretical formulas for the three DC-DC converter topologies under different fractional orders. A comprehensive comparison with the recently published literature is presented to show the advantages and disadvantages of each approach. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Magnetically coupled high-gain Y-source isolated DC/DC converter

DEFF Research Database (Denmark)

Siwakoti, Yam P.; Loh, Poh Chiang; Blaabjerg, Frede

2014-01-01

A new form of magnetically coupled DC/DC converter is proposed for medium power applications (250 W to 2 kW), requiring a high-voltage gain, short inductive charging time and galvanic isolation. The proposed converter can be realised using a unique Y-source impedance network and a two-switch push...

A large-aperture, low-resolution quadrupole separator for producing deposited cluster materials

CERN Document Server

Denby, P M

2000-01-01

A wide-aperture, low-resolution quadrupole separator for metal clusters is described. Its performance has been evaluated by numerical calculations of the trajectories of clusters. Operating in the frequency range from 5 to 100 KHz allows one to separate clusters in the mass range from 30000 to 300000 AMU and by suitable choice of the AC and DC voltages one can obtain a resolution of 0.15. At this resolution the transmission of clusters from a source is 100% over the selected mass range. By biasing the quadrupole it has been possible to obtain a very sharp cut-off between the transmitted clusters and those outside the selected range. Trajectory calculation for clusters deposited onto a biased 2 cm diameter substrate show that it is possible to keep the deposition energy below 25 eV for 90% of the clusters when the quadrupole is itself biased.

A large-aperture, low-resolution quadrupole separator for producing deposited cluster materials

Energy Technology Data Exchange (ETDEWEB)

Denby, P.M.; Eastham, D.A. E-mail: d.a.eastham@dl.ac.uk

2000-03-01

A wide-aperture, low-resolution quadrupole separator for metal clusters is described. Its performance has been evaluated by numerical calculations of the trajectories of clusters. Operating in the frequency range from 5 to 100 KHz allows one to separate clusters in the mass range from 30000 to 300000 AMU and by suitable choice of the AC and DC voltages one can obtain a resolution of 0.15. At this resolution the transmission of clusters from a source is 100% over the selected mass range. By biasing the quadrupole it has been possible to obtain a very sharp cut-off between the transmitted clusters and those outside the selected range. Trajectory calculation for clusters deposited onto a biased 2 cm diameter substrate show that it is possible to keep the deposition energy below 25 eV for 90% of the clusters when the quadrupole is itself biased.

A large-aperture, low-resolution quadrupole separator for producing deposited cluster materials

International Nuclear Information System (INIS)

Denby, P.M.; Eastham, D.A.

2000-01-01

A wide-aperture, low-resolution quadrupole separator for metal clusters is described. Its performance has been evaluated by numerical calculations of the trajectories of clusters. Operating in the frequency range from 5 to 100 KHz allows one to separate clusters in the mass range from 30000 to 300000 AMU and by suitable choice of the AC and DC voltages one can obtain a resolution of 0.15. At this resolution the transmission of clusters from a source is 100% over the selected mass range. By biasing the quadrupole it has been possible to obtain a very sharp cut-off between the transmitted clusters and those outside the selected range. Trajectory calculation for clusters deposited onto a biased 2 cm diameter substrate show that it is possible to keep the deposition energy below 25 eV for 90% of the clusters when the quadrupole is itself biased

A high voltage ratio and low ripple interleaved DC-DC converter for fuel cell applications.

Science.gov (United States)

Chang, Long-Yi; Chao, Kuei-Hsiang; Chang, Tsang-Chih

2012-01-01

This paper proposes a high voltage ratio and low ripple interleaved boost DC-DC converter, which can be used to reduce the output voltage ripple. This converter transfers the low DC voltage of fuel cell to high DC voltage in DC link. The structure of the converter is parallel with two voltage-doubler boost converters by interleaving their output voltages to reduce the voltage ripple ratio. Besides, it can lower the current stress for the switches and inductors in the system. First, the PSIM software was used to establish a proton exchange membrane fuel cell and a converter circuit model. The simulated and measured results of the fuel cell output characteristic curve are made to verify the correctness of the established simulation model. In addition, some experimental results are made to validate the effectiveness in improving output voltage ripple of the proposed high voltage ratio interleaved boost DC-DC converters.

DC Rocks! Using Place-Based Learning to Introduce Washington DC's K-12 Students to the Geosciences

Science.gov (United States)

Mayberry, G. C.; Mattietti, G. K.

2017-12-01

The Washington DC area has interesting geology and a multitude of agencies that deal with the geosciences, yet K-12 public school students in DC, most of whom are minorities, have limited exposure to the geosciences. Geoscience agencies in the DC area have a unique opportunity to address this by introducing the geosciences to local students who otherwise may not have such an opportunity, by highlighting the geology in the students' "backyard," and by leveraging partnerships among DC-based geoscience-related agencies. The USGS and George Mason University are developing a project called DC Rocks, which will give DC's students an exciting introduction into the world of geoscience with place-based learning opportunities that will make geoscience relevant to their lives and their futures. Both the need in DC and the potential for lasting impact are great; the geosciences have the lowest racial diversity of all the science, technology, engineering, and math (STEM) fields, 89% of students in DC public schools are minorities, and there is no dedicated geoscience curriculum in DC. DC Rocks aims to give these students early exposure to the earth sciences, and encourage them to consider careers in the profession. DC Rocks will work with partner agencies to apply several methods that are recommended by researchers to increase the participation of minority students in the geosciences, including providing profoundly positive experiences that spark interest in the geosciences (Levine et al., 2007); increasing students' sense of belonging in the geosciences (Huntoon, et al, 2016); and place-based teaching practices that emphasize the study of local sites (Semken, 2005), such as DC's Rock Creek Park. DC Rocks will apply these methods by coordinating local geoscientists and resources to provide real-world examples of the geosciences' impact on students' lives. Through the DC Rocks website, educators will be able to request geoscience-related resources such as class presentations by

Radiated electromagnetic emissions of DC-DC converters

International Nuclear Information System (INIS)

Feld, L; Jussen, R; Karpinski, W; Klein, K; Sammet, J; Wlochal, M

2010-01-01

For the CMS tracker at SLHC a new powering scheme is considered to be mandatory to allow the detector to provide at least the same performance as today at the LHC. The baseline solution of CMS foresees the use of DC-DC converters to provide larger currents with smaller losses. An important component of most converters are inductors which, however, tend to radiate the switching noise generated by the converter. The emissions of different inductors have been measured and simulated, the coil design has been optimized and noise susceptibility measurements, with present CMS hardware, have been performed. This article summarizes the results.

Field Trial on a Rack-mounted DC Power Supply System with 80-Ah Lithium-ion Batteries

Science.gov (United States)

Matsushima, Toshio

Using an industrial lithium-ion battery that has higher energy density than conventional valve-regulated lead-acid batteries, a rack-mounted DC-power-supply system was assembled and tested at a base transceiver station (BTS) offering actual services. A nominal output voltage and maximum output current of the system is 53.5V and 20A, respectively. An 80-Ah lithium-ion battery composed of 13 cells connected in series was applied in the system and maintained in a floating charge method. The DC-power-supply system was installed in a 19-inch power rack in the telecommunications equipment box at BTS. The characteristics of the 80Ah lithium-ion battery, specifications of the DC-power-supply system and field-test results were shown in this paper.

Modeling, Analysis and Control of Different DC-DC Converter Topologies for Photo Voltaic Emulator

Directory of Open Access Journals (Sweden)

Mohammad Tauquir Iqbal

2016-05-01

Full Text Available This paper presents the modeling, analysis and control of different DC-DC converter topologies to emulate the photovoltaic (PV system. A PV emulator is basically a DC-DC converter having same electrical characteristics that of solar PV panel.  The emulator helps to achieve real characteristics of PV system in a better way in an environment where using actual PV systems can produce inconsistent results due to variation in weather conditions. The paper describes different types of DC-DC converters like buck, Resonant and Quasi Resonant Converter. The complete system is modelled in MATLAB® Simulink SimPowerSystem software package. The Simulation results obtained from the MATLAB® Simulink SimPowerSystem software package for different topologies under steady and dynamic conditions are analyzed and presented. An evaluation table is also presented at the end of the paper, presenting the effectiveness of each topology.

Critical and Exponential Experiments on 19-Rod Clusters (R3 Fuel) in Heavy Water

Energy Technology Data Exchange (ETDEWEB)

Persson, R; Wikdahl, C E; Zadworski, Z

1962-03-15

Buckling measurements on clusters of 19 UO{sub 2} rods in heavy water have been performed in an exponential assembly and by means of substitution measurements in a critical facility. The material buckling was determined as a function of lattice pitch (range of V{sub mod} /V{sub fuel}: 7-22), internal spacing, void, and temperature (20 < T < 90 deg C). The change of diffusion coefficients (about 6-8 per cent) caused by voids was studied with single test fuel assemblies. The progressive substitution measurements have been analysed by means of a modified one-group perturbation theory in combination with an unconventional cell definition. The buckling differences between test and reference lattices are of the order of -1.0 to -3.5/m{sup 2}, The results of the exponential and the critical experiments are compared with similar measurements on the same kind of fuel at the Savannah River Laboratory. This comparison shows that the results of the various experiments agree quite well, whereas theoretical predictions fail in the extreme ranges.

5 kW, 5 kHz class-A inverter for DC accelerator in CAT, Indore (Paper No. CP 19)

International Nuclear Information System (INIS)

Thakurta, A.C.; Krishnaswamy, B.

1990-01-01

The 5 kHz, 5kW inverter described here is meant for energizing a high voltage transformer feeding a 2-stage Cockcroft-Walton multipliers with 100 kVDC output. This output is to be used as the acceleration voltage in DC accelerator at CAT, Indore. The load is expected to draw few tens of mA current, which means that with the values of the capacitors readily available with voltage ratings of 50 kVDC and above, there will be considerable drop in multiplier output voltage and ripple voltage also will be quite high, if one goes in for line-frequency operation. The frequency of 5 kHz suggests a good compromise between low ripple and DC drop, and the availability of devices switching at high frequency and handling kilowatts of power. The class A type of inverter which has reasonably good load regulation and tolerance to reactive loads was deemed suitable for generating this 5 kHz AC voltage. The DC voltage needed for the inverter was obtained from a phase-controlled supply which was put in closed loop to achieve regulation with respect to line and load variation. The output could be varied with external setting of a reference voltage. (author). 3 figs

Homopolar dc motor and trapped flux brushless dc motor using high temperature superconductor materials

Science.gov (United States)

Crapo, Alan D.; Lloyd, Jerry D.

1991-03-01

Two motors have been designed and built for use with high-temperature superconductor (HTSC) materials. They are a homopolar dc motor that uses HTSC field windings and a brushless dc motor that uses bulk HTSC materials to trap flux in steel rotor poles. The HTSC field windings of the homopolar dc motor are designed to operate at 1000 A/sq cm in a 0.010-T field. In order to maximize torque in the homopolar dc motor, an iron magnetic circuit with small air gaps gives maximum flux for minimum Ampere turns in the field. A copper field winding version of the homopolar dc motor has been tested while waiting for 575 A turn HTSC coils. The trapped flux brushless dc motor has been built and is ready to test melt textured bulk HTSC rings that are currently being prepared. The stator of the trapped flux motor will impress a magnetic field in the steel rotor poles with warm HTSC bulk rings. The rings are then cooled to 77 K to trap the flux in the rotor. The motor can then operate as a brushless dc motor.

Evolution of ferromagnetic interactions from cluster spin glass state in Co–Ga alloy

Energy Technology Data Exchange (ETDEWEB)

Mohammad Yasin, Sk. [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Saha, Ritwik [Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400005 (India); Srinivas, V., E-mail: veeturi@iitm.ac.in [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Kasiviswanathan, S. [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Nigam, A.K. [Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400005 (India)

2016-11-15

Low temperature magnetic properties of binary Co{sub x}Ga{sub 100−x} (x=54–57) alloy have been investigated. Analysis of frequency dependence of ac susceptibility provided a conclusive evidence for the existence of cluster spin glass like behavior with the freezing temperature ~8, 14 K for x=54, 55.5 respectively. The parameters for conventional ‘slowing down’ of the spin dynamics have been extracted from the acs data, which confirm the presence of glassy phase. The magnitude of Mydosh parameter obtained from the fits is larger than that reported for typical canonical spin glasses and smaller than those for non-interacting ideal superparamagnetic systems but comparable to those of known cluster-glass systems. Memory phenomena using specific cooling protocols also support the spin-glass features in Co{sub 55.5}Ga{sub 44.5} composition. Further the development of ferromagnetic clusters from the cluster spin glass state has been observed in x=57 composition. - Highlights: • Temperature dependence of DC and AC susceptibility (acs) analysis has been carried out on Co{sub x}Ga{sub 1−x,} (x=54–57). • M–H data above transition suggests presence of spin clusters. • A detailed analysis of acs data suggests a cluster glass behavior as oppose to SPM state for x=54 and 55.5. • Memory phenomena using specific cooling protocols also support the spin-glass features in Co{sub 55.5}Ga{sub 44.5} composition. • Development of ferromagnetic like behavior for x≥57 has been suggested from DC and AC magnetization data.

Electron correlation in the interacting quantum atoms partition via coupled-cluster lagrangian densities.

Science.gov (United States)

Holguín-Gallego, Fernando José; Chávez-Calvillo, Rodrigo; García-Revilla, Marco; Francisco, Evelio; Pendás, Ángel Martín; Rocha-Rinza, Tomás

2016-07-15

The electronic energy partition established by the Interacting Quantum Atoms (IQA) approach is an important method of wavefunction analyses which has yielded valuable insights about different phenomena in physical chemistry. Most of the IQA applications have relied upon approximations, which do not include either dynamical correlation (DC) such as Hartree-Fock (HF) or external DC like CASSCF theory. Recently, DC was included in the IQA method by means of HF/Coupled-Cluster (CC) transition densities (Chávez-Calvillo et al., Comput. Theory Chem. 2015, 1053, 90). Despite the potential utility of this approach, it has a few drawbacks, for example, it is not consistent with the calculation of CC properties different from the total electronic energy. To improve this situation, we have implemented the IQA energy partition based on CC Lagrangian one- and two-electron orbital density matrices. The development presented in this article is tested and illustrated with the H2 , LiH, H2 O, H2 S, N2 , and CO molecules for which the IQA results obtained under the consideration of (i) the CC Lagrangian, (ii) HF/CC transition densities, and (iii) HF are critically analyzed and compared. Additionally, the effect of the DC in the different components of the electronic energy in the formation of the T-shaped (H2 )2 van der Waals cluster and the bimolecular nucleophilic substitution between F(-) and CH3 F is examined. We anticipate that the approach put forward in this article will provide new understandings on subjects in physical chemistry wherein DC plays a crucial role like molecular interactions along with chemical bonding and reactivity. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Differential Mode EMI Filter Design for Isolated DC-DC Boost Converter

DEFF Research Database (Denmark)

Makda, Ishtiyaq Ahmed; Nymand, Morten

2014-01-01

A Differential Mode EMI filter for a low input voltage high-current isolated dc-dc boost converter is designed and presented in this paper. The primary side Differential Mode noise voltage is low due to the high transformer turn ratio, however, the input current is very high and since the EMI limit...... also does not change for such converters, it requires greatly optimized design approach for the filter including the correct sizing of the filter components. A complete analytical filter design process is carried out such a way that the Differential Mode noise voltage source in the converter...... is identified first. The DM noise model is then established and based on the harmonic analysis of the noise source voltage waveform, the complete Differential Mode EMI filter, including the filter resonance damping branch, is designed for a 3kW isolated dc-dc boost converter. The noise model and its theoretical...

Current Mode Control for LLC Series Resonant DC-to-DC Converters

Directory of Open Access Journals (Sweden)

Jinhaeng Jang

2015-06-01

Full Text Available Conventional voltage mode control only offers limited performance for LLC series resonant DC-to-DC converters experiencing wide variations in operational conditions. When the existing voltage mode control is employed, the closed-loop performance of the converter is directly affected by unavoidable changes in power stage dynamics. Thus, a specific control design optimized at one particular operating point could become unacceptable when the operational condition is varied. This paper presents a new current mode control scheme which could consistently provide good closed-loop performance for LLC resonant converters for the entire operational range. The proposed control scheme employs an additional feedback from the current of the resonant tank network to overcome the limitation of the existing voltage mode control. The superiority of the proposed current mode control over the conventional voltage mode control is verified using an experimental 150 W LLC series resonant DC-to-DC converter.

Application handbook for a Standardized Control Module (SCM) for DC-DC converters, volume 1

Science.gov (United States)

Lee, F. C.; Mahmoud, M. F.; Yu, Y.

1980-04-01

The standardized control module (SCM) was developed for application in the buck, boost and buck/boost DC-DC converters. The SCM used multiple feedback loops to provide improved input line and output load regulation, stable feedback control system, good dynamic transient response and adaptive compensation of the control loop for changes in open loop gain and output filter time constraints. The necessary modeling and analysis tools to aid the design engineer in the application of the SCM to DC-DC Converters were developed. The SCM functional block diagram and the different analysis techniques were examined. The average time domain analysis technique was chosen as the basic analytical tool. The power stage transfer functions were developed for the buck, boost and buck/boost converters. The analog signal and digital signal processor transfer functions were developed for the three DC-DC Converter types using the constant on time, constant off time and constant frequency control laws.

Application handbook for a Standardized Control Module (SCM) for DC-DC converters, volume 1

Science.gov (United States)

Lee, F. C.; Mahmoud, M. F.; Yu, Y.

1980-01-01

The standardized control module (SCM) was developed for application in the buck, boost and buck/boost DC-DC converters. The SCM used multiple feedback loops to provide improved input line and output load regulation, stable feedback control system, good dynamic transient response and adaptive compensation of the control loop for changes in open loop gain and output filter time constraints. The necessary modeling and analysis tools to aid the design engineer in the application of the SCM to DC-DC Converters were developed. The SCM functional block diagram and the different analysis techniques were examined. The average time domain analysis technique was chosen as the basic analytical tool. The power stage transfer functions were developed for the buck, boost and buck/boost converters. The analog signal and digital signal processor transfer functions were developed for the three DC-DC Converter types using the constant on time, constant off time and constant frequency control laws.

Design of PI Controlled Non Isolated Bidirectional DC to DC Converter for Electric Vehicle Application

Science.gov (United States)

Geetha, A.; Subramani, C.; Thamizh Thentral, T. M.; Krithika, V.; Usha, S.

2018-04-01

Non isolated Bidirectional DC-DC Converter (NIBDDC) is a good interface between DC source and inverter Fed induction motor drive. This paper deals with comparison between open loop and PI controlled Bidirectional DC to DC Converter Inverter System (BDDCIS). The modelling and control of BDDC is becomes an important issue. Open loop BDDCIS and closed loop PI controlled BDDCIS are designed, modelled and simulated using Matlab- simulink and their results are presented. The investigations indicate superior performance of PI controlled BDDCIS. The proposed BDDCIS has advantages like bidirectional power transfer ability, reduced hardware count and improved dynamic response.

Structural determinants of adhesion by Protocadherin-19 and implications for its role in epilepsy

Energy Technology Data Exchange (ETDEWEB)

Cooper, Sharon R.; Jontes, James D.; Sotomayor, Marcos

2016-10-26

Non-clustered δ-protocadherins are homophilic cell adhesion molecules essential for the development of the vertebrate nervous system, as several are closely linked to neurodevelopmental disorders. Mutations inprotocadherin-19(PCDH19) result in a female-limited, infant-onset form of epilepsy (PCDH19-FE). Over 100 mutations inPCDH19have been identified in patients with PCDH19-FE, about half of which are missense mutations in the adhesive extracellular domain. Neither the mechanism of homophilic adhesion by PCDH19, nor the biochemical effects of missense mutations are understood. Here we present a crystallographic structure of the minimal adhesive fragment of the zebrafish Pcdh19 extracellular domain. This structure reveals the adhesive interface for Pcdh19, which is broadly relevant to both non-clustered δ and clustered protocadherin subfamilies. In addition, we show that several PCDH19-FE missense mutations localize to the adhesive interface and abolish Pcdh19 adhesion inin vitroassays, thus revealing the biochemical basis of their pathogenic effects during brain development.

Application of Distributed DC/DC Electronics in Photovoltaic Systems

Science.gov (United States)

Kabala, Michael

In a typical residential, commercial or utility grade photovoltaic (PV) system, PV modules are connected in series and in parallel to form an array that is connected to a standard DC/AC inverter, which is then connected directly to the grid. This type of standard installation; however, does very little to maximize the energy output of the solar array if certain conditions exist. These conditions could include age, temperature, irradiance and other factors that can cause mismatch between PV modules in an array that severely cripple the output power of the system. Since PV modules are typically connected in series to form a string, the output of the entire string is limited by the efficiency of the weakest module. With PV module efficiencies already relatively low, it is critical to extract the maximum power out of each module in order to make solar energy an economically viable competitor to oil and gas. Module level DC/DC electronics with maximum power point (MPP) tracking solves this issue by decoupling each module from the string in order for the module to operate independently of the geometry and complexity of the surrounding system. This allows each PV module to work at its maximum power point by transferring the maximum power the module is able to deliver directly to the load by either boosting (stepping up) the voltage or bucking (stepping down) the voltage. The goal of this thesis is to discuss the development of a per-module DC/DC converter in order to maximize the energy output of a PV module and reduce the overall cost of the system by increasing the energy harvest.

Quasiperiodicity and Torus Breakdown in a Power Electronic DC/DC Converter

DEFF Research Database (Denmark)

Zhusubaliyev, Zhanybai; Soukhoterin, Evgeniy; Mosekilde, Erik

2007-01-01

This paper discusses the mechanisms of torus formation and torus destruction in a dc/dc converter with relay control and hysteresis. We establish a chart of the dynamical modes in the input voltage versus load resistance parameter plane. This chart displays several different torus bifurcations...

DC Distribution Systems and Microgrids

DEFF Research Database (Denmark)

Dragicevic, Tomislav; Anvari-Moghaddam, Amjad; Quintero, Juan Carlos Vasquez

2017-01-01

summarized. Due to its attractive characteristics in terms of compliance with modern generation, storage and electronic load technologies, high reliability and current carrying capacity, as well as simple control, DC systems are already an indispensable part of power systems. Moreover, the existing......A qualitative overview of different hardware topologies and control systems for DC MGs has been presented in this chapter. Some challenges and design considerations of DC protections systems have also been discussed. Finally, applications of DC MGs in emerging smart grid applications have been...... challenges such as protection issues will be effectively resolved in the near future due to fast progress of semiconductor technology which is a key enabler cheap and reliable future DC solid-state protection systems. Therefore, it is the view of the author that more and more DC systems will appear...

Analysis of the Coupling Behavior of PEM Fuel Cells and DC-DC Converters

Directory of Open Access Journals (Sweden)

Achim Kienle

2009-03-01

Full Text Available The connection between PEM fuel cells and common DC-DC converters is examined. The analysis is model-based and done for boost, buck and buck-boost converters. In a first step, the effect of the converter ripples upon the PEM fuel cell is shown. They introduce oscillations in the fuel cell. Their appearance is explained, discussed and possibilities for their suppression are given. After that, the overall behaviors of the coupled fuel cell-converter systems are analyzed. It is shown, that neither stationary multiplicities nor oscillations can be introduced by the couplings and therefore separate control approaches for both the PEMFC and the DC-DC converters are applicable.

Single Event Burnout in DC-DC Converters for the LHC Experiments

Energy Technology Data Exchange (ETDEWEB)

Claudio H. Rivetta et al.

2001-09-24

High voltage transistors in DC-DC converters are prone to catastrophic Single Event Burnout in the LHC radiation environment. This paper presents a systematic methodology to analyze single event effects sensitivity in converters and proposes solutions based on de-rating input voltage and output current or voltage.

Area-Efficiency Trade-Offs in Integrated Switched-Capacitor DC-DC Converters

DEFF Research Database (Denmark)

Spliid, Frederik Monrad; Larsen, Dennis Øland; Knott, Arnold

2016-01-01

This paper analyzes the relationship between efficiency and chip area in a fully integrated switched capacitor voltage divider dc-dc converter implemented in 180nm-technology and a 1/2 topology. A numerical algorithm for choosing the optimal sizes of individual components, in terms of power loss...

Egr2 induced during DC development acts as an intrinsic negative regulator of DC immunogenicity.

Science.gov (United States)

Miah, Mohammad Alam; Byeon, Se Eun; Ahmed, Md Selim; Yoon, Cheol-Hee; Ha, Sang-Jun; Bae, Yong-Soo

2013-09-01

Early growth response gene 2 (Egr2), which encodes a zinc finger transcription factor, is rapidly and transiently induced in various cell types independently of de novo protein synthesis. Although a role for Egr2 is well established in T-cell development, Egr2 expression and its biological function in dendritic cells (DCs) have not yet been described. Here, we demonstrate Egr2 expression during DC development, and its role in DC-mediated immune responses. Egr2 is expressed in the later stage of DC development from BM precursor cells. Even at steady state, Egr2 is highly expressed in mouse splenic DCs. Egr2-knockdown (Egr2-KD) DCs showed increased levels of major histocompatability complex (MHC) class I and II and co-stimulatory molecules, and enhanced antigen uptake and migratory capacities. Furthermore, Egr2-KD abolished SOCS1 expression and signal transducer and activator of transcription 5 (STAT5) activation during DC development, probably resulting in the enhancement of IL-12 expression and Th1 immunogenicity of a DC vaccine. DC-mediated cytotoxic T lymphocyte (CTL) activation and antitumor immunity were significantly enhanced by Egr2-KD, and impaired by Egr2 overexpression in antigen-pulsed DC vaccines. These data suggest that Egr2 acts as an intrinsic negative regulator of DC immunogenicity and can be an attractive molecular target for DC vaccine development. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Impact of DC link control strategies on the power-flow convergence of integrated AC–DC systems

Directory of Open Access Journals (Sweden)

Shagufta Khan

2016-03-01

Full Text Available For the power-flow solution of integrated AC–DC systems, five quantities are required to be solved per converter, against three independent equations available. These three equations consist of two basic converter equations and one DC network equation, corresponding to each converter. Thus, for solution, two additional equations are required. These two equations are derived from the control specifications adopted for the DC link. Depending on the application, several combinations of valid control specifications are possible. A set of valid control specifications constitutes a control strategy. It is observed that the control strategy adopted for the DC link strongly affects the power-flow convergence of integrated AC–DC systems. This paper investigates how different control strategies affect the power flow convergence of integrated AC–DC systems. Sequential method is used to solve the DC variables in the Newton Raphson (NR power flow model. Seven typical control strategies have been taken into consideration. This is validated by numerous case studies carried out with multiple DC links incorporated in the IEEE 118-bus and 300-bus test systems.

Investigation of DC-DC Boost Converter for Reliability of Operational Planning

DEFF Research Database (Denmark)

Khazraj, Hesam; Ashouri, Mani; Silva, Filipe Miguel Faria da

2018-01-01

of the interests related to reliability is the power semiconductor switches, which are the most vulnerable elements. The failure of one-power switches can reduce the system reliability. Interleaved technique for DC-DC converters is a redundant strategy to improve the reliability, but at the cost of increasing...

Comparison of solar panel cooling system by using dc brushless fan and dc water

International Nuclear Information System (INIS)

Irwan, Y M; Leow, W Z; Irwanto, M; M, Fareq; Hassan, S I S; Amelia, A R; Safwati, I

2015-01-01

The purpose of this article is to discuss comparison of solar panel cooling system by using DC brushless fan and DC water pump. Solar photovoltaic (PV) power generation is an interesting technique to reduce non-renewable energy consumption and as a renewable energy. The temperature of PV modules increases when it absorbs solar radiation, causing a decrease in efficiency. A solar cooling system is design, construct and experimentally researched within this work. To make an effort to cool the PV module, Direct Current (DC) brushless fan and DC water pump with inlet/outlet manifold are designed for constant air movement and water flow circulation at the back side and front side of PV module representatively. Temperature sensors were installed on the PV module to detect temperature of PV. PIC microcontroller was used to control the DC brushless fan and water pump for switch ON or OFF depend on the temperature of PV module automatically. The performance with and without cooling system are shown in this experiment. The PV module with DC water pump cooling system increase 3.52%, 36.27%, 38.98%in term of output voltage, output current, output power respectively. It decrease 6.36 °C compare than to PV module without DC water pump cooling system. While DC brushless fan cooling system increase 3.47%, 29.55%, 32.23%in term of output voltage, output current, and output power respectively. It decrease 6.1 °C compare than to PV module without DC brushless fan cooling system. The efficiency of PV module with cooling system was increasing compared to PV module without cooling system; this is because the ambient temperature dropped significantly. The higher efficiency of PV cell, the payback period of the system can be shorted and the lifespan of PV module can also be longer. (paper)

New Fast Lane towards Discoveries of Clusters of Galaxies Inaugurated

Science.gov (United States)

2003-07-01

Space and Ground-Based Telescopes Cooperate to Gain Deep Cosmological Insights Summary Using the ESA XMM-Newton satellite, a team of European and Chilean astronomers [2] has obtained the world's deepest "wide-field" X-ray image of the cosmos to date. This penetrating view, when complemented with observations by some of the largest and most efficient ground-based optical telescopes, including the ESO Very Large Telescope (VLT), has resulted in the discovery of several large clusters of galaxies. These early results from an ambitious research programme are extremely promising and pave the way for a very comprehensive and thorough census of clusters of galaxies at various epochs. Relying on the foremost astronomical technology and with an unequalled observational efficiency, this project is set to provide new insights into the structure and evolution of the distant Universe. PR Photo 19a/03: First image from the XMM-LSS survey. PR Photo 19b/03: Zoom-in on PR Photo 19b/03. PR Photo 19c/03: XMM-Newton contour map of the probable extent of a cluster of galaxies, superimposed upon a CHFT I-band image. PR Photo 19d/03: Velocity distribution in the cluster field shown in PR Photo 19c/03. The universal web Unlike grains of sand on a beach, matter is not uniformly spread throughout the Universe. Instead, it is concentrated into galaxies which themselves congregate into clusters (and even clusters of clusters). These clusters are "strung" throughout the Universe in a web-like structure, cf. ESO PR 11/01. Our Galaxy, the Milky Way, for example, belongs to the so-called Local Group which also comprises "Messier 31", the Andromeda Galaxy. The Local Group contains about 30 galaxies and measures a few million light-years across. Other clusters are much larger. The Coma cluster contains thousands of galaxies and measures more than 20 million light-years. Another well known example is the Virgo cluster, covering no less than 10 degrees on the sky ! Clusters of galaxies are the most

75 FR 47199 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-9-10 Series Airplanes, DC-9-30...

Science.gov (United States)

2010-08-05

... Airworthiness Directives; McDonnell Douglas Corporation Model DC- 9-10 Series Airplanes, DC-9-30 Series... existing airworthiness directive (AD), which applies to all McDonnell Douglas Model DC-9-10 series..., 2010). That AD applies to all McDonnell Douglas Corporation Model DC-9-10 series airplanes, DC-9-30...

A Novel Single Switch Transformerless Quadratic DC/DC Buck-Boost Converter

DEFF Research Database (Denmark)

Mostaan, Ali; A. Gorji, Saman; N. Soltani, Mohsen

2017-01-01

A novel quadratic buck-boost DC/DC converter is presented in this study. The proposed converter utilizes only one active switch and can step-up/down the input voltage, while the existing single switch quadratic buck/boost converters can only work in step-up or step-down mode. First, the proposed ...

DC conductivity and Seebeck coefficient of nonstoichiometric MgCuZn ferrites

Directory of Open Access Journals (Sweden)

Madhuri W.

2017-02-01

Full Text Available Nonstoichiometric series of Mg0.5−xCuxZn0.5Fe1.9O4−δ where x = 0.0, 0.1, 0.15, 0.2 and 0.25 has been synthesized by conventional solid state reaction route. The single phase spinel structure of the double sintered ferrites was confirmed by X-ray diffraction patterns (XRD. The ferrite series was studied in terms of DC electrical conductivity and thermoelectric power in the temperature ranging from room temperature to 300 °C and 400 °C, respectively. It was observed that DC electrical conductivity and Seebeck coefficient α decreased with the increase in x. DC electrical conductivity was found to decrease by about 4 orders. All the compositions showed a negative Seebeck coefficient exhibiting n-type semiconducting nature. From the above experimental results, activation energy and mobility of all the samples were estimated. Small polaron hopping conduction mechanism was suggested for the series of ferrites. Owing to their low conductivity the nonstoichiometric MgCuZn ferrites are the best materials for transformer core and high definition television deflection yokes.

Drilling history core hole DC-8

International Nuclear Information System (INIS)

1978-10-01

Core hole DC-8 was completed in August, 1978 by Boyles Brothers Drilling Company, Spokane, Washington, under subcontract to Fenix and Scission, Inc. The hole was cored for the US Department of Energy and the Rockwell Hanford Operations' Basalt Waste Isolation Program. Fenix and Scisson, Inc. furnished the engineering, daily supervision of the core drilling activities, and geologic core logging for hole DC-8. Core hole DC-8 is located on the Hanford Site near the Wye Barricade and 50 feet northwest of rotary hole DC-7. The Hanford Site vation coordinates for DC-8 are North 14,955.94 feet and West 14,861.92 coordinates for DC-8 are North 14,955.94 feet and West 14,861.92 mean sea level. The purpose of core hole DC-8 was to core drill vertically through the basalt and interbed units for stratigraphic depth determination and core collection, and to provide a borehole for hydrologic testing and cross-hole seismic shear and pressure wave velocity studies with rotary hole DC-7. The total depth of core hole DC-8 was 4100.5 feet. Core recovery exceeded 97 percent of the total footage cored

Drilling history core hole DC-8

Energy Technology Data Exchange (ETDEWEB)

1978-10-01

Core hole DC-8 was completed in August, 1978 by Boyles Brothers Drilling Company, Spokane, Washington, under subcontract to Fenix and Scission, Inc. The hole was cored for the US Department of Energy and the Rockwell Hanford Operations' Basalt Waste Isolation Program. Fenix and Scisson, Inc. furnished the engineering, daily supervision of the core drilling activities, and geologic core logging for hole DC-8. Core hole DC-8 is located on the Hanford Site near the Wye Barricade and 50 feet northwest of rotary hole DC-7. The Hanford Site vation coordinates for DC-8 are North 14,955.94 feet and West 14,861.92 coordinates for DC-8 are North 14,955.94 feet and West 14,861.92 mean sea level. The purpose of core hole DC-8 was to core drill vertically through the basalt and interbed units for stratigraphic depth determination and core collection, and to provide a borehole for hydrologic testing and cross-hole seismic shear and pressure wave velocity studies with rotary hole DC-7. The total depth of core hole DC-8 was 4100.5 feet. Core recovery exceeded 97 percent of the total footage cored.

Characterization of diode valve in medium voltage dc/dc converter for wind turbines

DEFF Research Database (Denmark)

Dincan, Catalin Gabriel; Kjær, Philip Carne

2016-01-01

This paper proposes a methodology for characterization of medium voltage (MV), medium frequency (MF) rectifier diode valve. The intended application is for 10MW dc/dc converters used in DC offshore wind turbines. Sensitivity to semiconductor component parameter variation, snubber component tolera...... tolerance, influence of temperature and stray capacitance are analyzed. It is concluded that the largest impact on sensitivity is given by reverse recovery charge variation and differences of temperature between adjacent devices....

Operation and control of a DC-grid offshore wind farm under DC transmission system faults

DEFF Research Database (Denmark)

Deng, Fujin; Chen, Zhe

2013-01-01

. Consequently, the protection and control strategies of dc systems need to be established. This paper studies a dc-grid offshore wind farm, where the wind power collection system and power transmission system adopt dc technology. In this paper, the redundancy of the HVDC transmission system under faults...... is studied, and a fault ridethrough strategy for the dc-grid offshore wind farm is proposed. The proposed strategy can effectively minimize the impacts of the power transmission system disturbance on the offshore wind farm, and on the ac grid. A dc-grid offshore wind farm example is simulated with PSCAD....../EMTDC, and the results validate the feasibility of the presented redundancy configuration and operation approach, and the fault ridethrough control strategy....

Open- and Short-Circuit Fault Identification for a Boost dc/dc Converter in PV MPPT Systems

Directory of Open Access Journals (Sweden)

Diego R. Espinoza Trejo

2018-03-01

Full Text Available This paper proposes a fault identification system for short and open-circuit switch faults (SOCSF for a dc/dc converter acting as a Maximum Power Point Tracker (MPPT in Photovoltaic (PV systems. A closed-loop operation is assumed for the boost dc/dc converter. A linearizing control plus a Proportional-Derivative (PD controller is suggested for PV voltage regulation at the maximum power point (MPP. In this study, the SOCSF are modeled by using an additive fault representation and the fault identification (FI system is synthesized departing from a Luenberger observer. Hence, an FI signal is obtained, which is insensitive to irradiance and load current changes, but affected by the SOCSF. For FI purposes, only the sensors used in the control system are needed. Finally, an experimental evaluation is presented by using a solar array simulator dc power supply and a boost dc/dc converter of 175 W in order to validate the ideas this study exposes.

Research on Two-channel Interleaved Two-stage Paralleled Buck DC-DC Converter for Plasma Cutting Power Supply

DEFF Research Database (Denmark)

Yang, Xi-jun; Qu, Hao; Yao, Chen

2014-01-01

As for high power plasma power supply, due to high efficiency and flexibility, multi-channel interleaved multi-stage paralleled Buck DC-DC Converter becomes the first choice. In the paper, two-channel interleaved two- stage paralleled Buck DC-DC Converter powered by three-phase AC power supply...

Dielectric-spectroscopy approach to ferrofluid nanoparticle clustering induced by an external electric field.

Science.gov (United States)

Rajnak, Michal; Kurimsky, Juraj; Dolnik, Bystrik; Kopcansky, Peter; Tomasovicova, Natalia; Taculescu-Moaca, Elena Alina; Timko, Milan

2014-09-01

An experimental study of magnetic colloidal particles cluster formation induced by an external electric field in a ferrofluid based on transformer oil is presented. Using frequency domain isothermal dielectric spectroscopy, we study the influence of a test cell electrode separation distance on a low-frequency relaxation process. We consider the relaxation process to be associated with an electric double layer polarization taking place on the particle surface. It has been found that the relaxation maximum considerably shifts towards lower frequencies when conducting the measurements in the test cells with greater electrode separation distances. As the electric field intensity was always kept at a constant value, we propose that the particle cluster formation induced by the external ac electric field accounts for that phenomenon. The increase in the relaxation time is in accordance with the Schwarz theory of electric double layer polarization. In addition, we analyze the influence of a static electric field generated by dc bias voltage on a similar shift in the relaxation maximum position. The variation of the dc electric field for the hysteresis measurements purpose provides understanding of the development of the particle clusters and their decay. Following our results, we emphasize the utility of dielectric spectroscopy as a simple, complementary method for detection and study of clusters of colloidal particles induced by external electric field.

Pulsed-DC selfsputtering of copper

International Nuclear Information System (INIS)

Wiatrowski, A; Posadowski, W M; Radzimski, Z J

2008-01-01

At standard magnetron sputtering conditions (argon pressure ∼0.5 Pa) inert gas particles are often entrapped in the formed films. Inert gas contamination can be eliminated by using the self-sustained magnetron sputtering process because it is done in the absence of the inert gas atmosphere. The self-sustained sputtering (SSS) gives also a unique condition during the transport of sputtered particles to the substrate. It is especially useful for filling high aspect ratio submicron scale structures for microelectronics. So far it has been shown that the self-sputtering process can be sustained in the DC operation mode (DC-SSS) only. The main disadvantage of DC-SSS process is instability related to possible arc formation. Usage of pulsed sputtering, similarly to reactive pulsed magnetron sputtering, could eliminate this problem. In this paper results of pulsed-DC self-sustained magnetron sputtering (pulsed DC-SSS) of copper are presented for the first time. The planar magnetron equipped with a 50 mm in diameter and 6 mm thick copper target was powered by DC-power supply modulated by power switch. The maximum target power was about 11 kW (∼550W/cm 2 ). The magnetron operation was investigated as a function of pulsing frequency (20-100 kHz) and duty factor (50-90%). The discharge extinction pressure was determined for these conditions. The plasma emission spectra (400-410nm range) and deposition rates were observed for both DC and pulsed DC sustained self-sputtering processes. The presented results illustrate that stable pulsed DC-SSS process can be obtained at pulsing frequency in the range of 60-100 kHz and duty factor of 70-90%

Pulsed-DC selfsputtering of copper

Science.gov (United States)

Wiatrowski, A.; Posadowski, W. M.; Radzimski, Z. J.

2008-03-01

At standard magnetron sputtering conditions (argon pressure ~0.5 Pa) inert gas particles are often entrapped in the formed films. Inert gas contamination can be eliminated by using the self-sustained magnetron sputtering process because it is done in the absence of the inert gas atmosphere. The self-sustained sputtering (SSS) gives also a unique condition during the transport of sputtered particles to the substrate. It is especially useful for filling high aspect ratio submicron scale structures for microelectronics. So far it has been shown that the self-sputtering process can be sustained in the DC operation mode (DC-SSS) only. The main disadvantage of DC-SSS process is instability related to possible arc formation. Usage of pulsed sputtering, similarly to reactive pulsed magnetron sputtering, could eliminate this problem. In this paper results of pulsed-DC self-sustained magnetron sputtering (pulsed DC-SSS) of copper are presented for the first time. The planar magnetron equipped with a 50 mm in diameter and 6 mm thick copper target was powered by DC-power supply modulated by power switch. The maximum target power was about 11 kW (~550W/cm2). The magnetron operation was investigated as a function of pulsing frequency (20-100 kHz) and duty factor (50-90%). The discharge extinction pressure was determined for these conditions. The plasma emission spectra (400-410nm range) and deposition rates were observed for both DC and pulsed DC sustained self-sputtering processes. The presented results illustrate that stable pulsed DC-SSS process can be obtained at pulsing frequency in the range of 60-100 kHz and duty factor of 70-90%.

DC injection into low voltage AC networks

Energy Technology Data Exchange (ETDEWEB)

NONE

2005-07-01

This report summarises the results of a study investigating the impact of levels of injected DC current injections on a low voltage AC distribution network systems in order to recommend acceptable limits of DC from microgeneration. Relevant literature is reviewed, and the impact of DC levels in distribution transformers, transformer modelling, and instrumental transformers are discussed. The impact of DC in residual current devices (RCD) and in domestic electricity watt hour meters is examined along with DC enhanced corrosion, corrosion failure, and the measurement of DC current injection. Sources of DC injection outlined include DC from computer power supplies, network faults, geomagnetic phenomena, lighting circuits/dimmers, and embedded generators.

Three-nucleon transfer reactions and cluster structure in the A = 15 to A = 19 nuclei

International Nuclear Information System (INIS)

Martz, L.M.

1978-01-01

The ( 6 Li,t) and ( 6 Li, 3 He) reactions were studied on targets of 12 C, 13 C, 14 N, 15 N, and 16 O at E/sub Li/ approx. = 44 MeV and theta/sub lab/ approx. = 15 0 . A preferential population of final states was exhibited in spectra for the A = 15 to A = 19 nuclei. The strong forward peaking of angular distributions in the 13 C( 6 Li,t) 16 O and 13 C( 6 Li, 3 He) 16 N reactions can be reproduced by DWBA calculations but not by the Hauser-Feshbach model. Such indications of a primarily direct mechanism at forward angles suggest use of these three-nucleon-transfer reactions to identify candidates for 3p-nh states. A comparison with other multinucleon transfer data, e.g., those from ( 7 Li,α) and ( 7 Li,t) reactions on 13 C and 15 N targets, further tests dominant particle-hole configurations. The relationship between ( 6 Li,t) and ( 6 Li, 3 He) spectra reveals analog states, notably T = 1, T/sub z/ = 0 levels at high excitation in 16 O. Nuclear theory is used to investigate the role of triton clustering in such structure. The 2N + L = 6 band predicted by a folded-potential model of 18 O = 15 N + t shows an underlying correspondence to the experimental levels in triton-transfer data. Triton spectroscopic factors calculated from the SU(3) shell model further suggest the broad influence of clustering phenomena in this mass region. Experimental evidence of systematic behavior in the triton binding energies of proposed p/sup -n/(sd) 3 configurations was found

Supersymmetry for nuclear cluster systems

International Nuclear Information System (INIS)

Levai, G.; Cseh, J.; Van Isacker, P.

2001-01-01

A supersymmetry scheme is proposed for nuclear cluster systems. The bosonic sector of the superalgebra describes the relative motion of the clusters, while its fermionic sector is associated with their internal structure. An example of core+α configurations is discussed in which the core is a p-shell nucleus and the underlying superalgebra is U(4/12). The α-cluster states of the nuclei 20 Ne and 19 F are analysed and correlations between their spectra, electric quadrupole transitions, and one-nucleon transfer reactions are interpreted in terms of U(4/12) supersymmetry. (author)

CHEMICAL AND PHYSICAL CONDITIONS IN MOLECULAR CLOUD CORE DC 000.4-19.5 (SL42) IN CORONA AUSTRALIS

Energy Technology Data Exchange (ETDEWEB)

Hardegree-Ullman, E.; Whittet, D. C. B. [New York Center for Astrobiology and Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180 (United States); Harju, J. [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Vaeisaelaentie 20, FI-21500, Piikkioe (Finland); Juvela, M.; Sipilae, O. [Department of Physics, P.O. Box 64, FI-00014, University of Helsinki (Finland); Hotzel, S., E-mail: hardee@rpi.edu [Observatory, FI-00014, University of Helsinki (Finland)

2013-01-20

Chemical reactions in starless molecular clouds are heavily dependent on interactions between gas phase material and solid phase dust and ices. We have observed the abundance and distribution of molecular gases in the cold, starless core DC 000.4-19.5 (SL42) in Corona Australis using data from the Swedish ESO Submillimeter Telescope. We present column density maps determined from measurements of C{sup 18}O (J = 2-1, 1-0) and N{sub 2}H{sup +} (J = 1-0) emission features. Herschel data of the same region allow a direct comparison to the dust component of the cloud core and provide evidence for gas phase depletion of CO at the highest extinctions. The dust color temperature in the core calculated from Herschel maps ranges from roughly 10.7 to 14.0 K. This range agrees with the previous determinations from Infrared Space Observatory and Planck observations. The column density profile of the core can be fitted with a Plummer-like density distribution approaching n(r) {approx} r {sup -2} at large distances. The core structure deviates clearly from a critical Bonnor-Ebert sphere. Instead, the core appears to be gravitationally bound and to lack thermal and turbulent support against the pressure of the surrounding low-density material: it may therefore be in the process of slow contraction. We test two chemical models and find that a steady-state depletion model agrees with the observed C{sup 18}O column density profile and the observed N(C{sup 18}O) versus A{sub V} relationship.

Experimental Results of a DC Bus Voltage Level Control for a Load-Controlled Marine Current Energy Converter

Directory of Open Access Journals (Sweden)

Johan Forslund

2015-05-01

Full Text Available This paper investigates three load control methods for a  marine current energy converter using a vertical axis current  turbine (VACT mounted on a permanent magnet synchronous generator  (PMSG. The three cases are; a fixed AC load, a fixed pulse width  modulated (PWM DC load and DC bus voltage control of a DC  load. Experimental results show that the DC bus voltage control  reduces the variations of rotational speed by a factor of 3.5 at the cost  of slightly increased losses in the generator and transmission lines.  For all three cases, the tip speed ratio \\(\\lambda\\ can be kept close to  the expected \\(\\lambda_{opt}\\. The power coefficient is estimated to be  0.36 at \\(\\lambda_{opt}\\; however, for all three cases, the average  extracted power was about \\(\\sim 19\\\\%. A maximum power point  tracking (MPPT system, with or without water velocity measurement,  could increase the average extracted power.

Structure of small rare earth clusters

International Nuclear Information System (INIS)

Rayane, D.; Benamar, A.; Tribollet, B.; Broyer, M.; Melinon, P.

1991-01-01

Rare earth clusters are produced by the inert gas condensation technique. The observed size distribution shows large peaks at n=13, 19, 23, 26, 29, 32, 34, 37, 39, 45, .... The beginning of this sequence (up to 34) has been already observed in argon clusters and recently by our group in barium clusters; this sequence may be interpreted in terms of icosahedral structures corresponding to the addition of caps on a core icosahedron of 13 atoms. (orig.)

DC-Compensated Current Transformer.

Science.gov (United States)

Ripka, Pavel; Draxler, Karel; Styblíková, Renata

2016-01-20

Instrument current transformers (CTs) measure AC currents. The DC component in the measured current can saturate the transformer and cause gross error. We use fluxgate detection and digital feedback compensation of the DC flux to suppress the overall error to 0.15%. This concept can be used not only for high-end CTs with a nanocrystalline core, but it also works for low-cost CTs with FeSi cores. The method described here allows simultaneous measurements of the DC current component.

High voltage dc cables

Energy Technology Data Exchange (ETDEWEB)

Bjustrom, B

1965-12-01

How stress distribution in dc cables varies with temperature and stress level, influence of polarity reversals and space charges, and different types of overvoltage to which dc cable may be subjected are discussed. Design problems, especially as related to corrosion protection and to mechanical stress caused by wire armoring during manufacturing and laying, accessories and work done on test methods, and the possibility of designing 400 to 600 kV dc cables for transmitting 2000 to 4000 MW are described.

Comparative evaluation of bidirectional dual active bridge DC-DC converter variants

NARCIS (Netherlands)

Sfakianakis, G.; Everts, J.; Huisman, H.; Lomonova, E.A.

2016-01-01

For the realization of DC-DC converters in automotive industry, the Dual Active Bridge (DAB) converter seems to be a promising choice because of its soft-switching and high-power-density capability. Contrary to the traditional 3 level - 3 level (3-3L) DAB, a 3 level - 5 level (3-5L) DAB can operate

Improvement of burst-mode control of piezoelectric transformer based DC/DC converter

International Nuclear Information System (INIS)

Vasic, Dejan; Liu, Yuan-Ping; Costa, François; Schwander, Denis; Wu, Wen-Jong

2013-01-01

Burst-mode operation is adopted sometimes in piezoelectric transformer based converters for two major purposes: (1) to achieve voltage regulation in DC/DC converters and (2) to achieve dimming control in backlight inverters. Burst-mode control enables the converter to operate at a constant switching frequency as well as to maintain good efficiency at light load conditions. However, in practice, the piezoelectric transformer cannot instantly stop vibrating in the burst-mode due to its high quality factor. The delay in the output voltage change resulting from this behavior influences the accuracy of the regulation. This paper proposes a control strategy to make the piezoelectric transformer stop more quickly so as to enhance the accuracy of burst-mode control. The proposed method only modifies the control signal of the burst-mode driving circuit. The proposed control strategy is verified by experiments in a step-down 9 W DC/DC converter. (paper)

Modular Power System Configured with Standard Product Hybrid DC-DC Converters, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — VPT proposes an innovative concept whereby complex NASA space power electronic systems can be configured using a small number of qualified hybrid DC-DC converter and...

DIAGNOSTIC/PROGNOSTIC EXPERIMENTS FOR CAPACITOR DEGRADATION AND HEALTH MONITORING IN DC-DC CONVERTERS

Data.gov (United States)

National Aeronautics and Space Administration — Studying and analyzing the ageing mechanisms of electronic components avionics in systems such as the GPS and INAV are of critical importance. In DC-DC power...

Simulating and Testing a DC-DC Half-Bridge SLR Converter

Science.gov (United States)

2013-06-01

future pulse power demands with ship power, a large bank of capacitors or similar rapid discharge source is required. If capacitors are charged...Single Pulsed Avalanche Energy (j) I" Avalanche Current (i) E,, Repetilive Avalanche Energy (i) dv/dt Peak Diode Recovery dv/dt ® Po Total Power...SLR), battery charging, DC-DC, pulse power, power electronics, SLR converter 15. NUMBER OF PAGES 119 16. PRICE CODE 17. SECURITY CLASSIFICATION

Efficient Visible Light Communication Transmitters Based on Switching-Mode dc-dc Converters

Science.gov (United States)

2018-01-01

Visible light communication (VLC) based on solid-state lighting (SSL) is a promising option either to supplement or to substitute existing radio frequency (RF) wireless communication in indoor environments. VLC systems take advantage of the fast modulation of the visible light that light emitting diodes (LEDs) enable. The switching-mode dc-to-dc converter (SMCdc-dc) must be the cornerstone of the LED driver of VLC transmitters in order to incorporate the communication functionality into LED lighting, keeping high power efficiency. However, the new requirements related to the communication, especially the high bandwidth that the LED driver must achieve, converts the design of the SMCdc-dc into a very challenging task. In this work, three different methods for achieving such a high bandwidth with an SMCdc-dc are presented: increasing the order of the SMCdc-dc output filter, increasing the number of voltage inputs, and increasing the number of phases. These three strategies are combinable and the optimum design depends on the particular VLC application, which determines the requirements of the VLC transmitter. As an example, an experimental VLC transmitter based on a two-phase buck converter with a fourth-order output filter will demonstrate that a bandwidth of several hundred kilohertz (kHz) can be achieved with output power levels close to 10 W and power efficiencies between 85% and 90%. In conclusion, the design strategy presented allows us to incorporate VLC into SSL, achieving high bit rates without damaging the power efficiency of LED lighting. PMID:29642455

DC-Voltage Fluctuation Elimination Through a DC-Capacitor Current Control for DFIG Converters Under Unbalanced Grid Voltage Conditions

DEFF Research Database (Denmark)

Liu, Changjin; Xu, Dehong; Zhu, Nan

2013-01-01

Unbalanced grid voltage causes a large second-order harmonic current in the dc-link capacitors as well as dc-voltage fluctuation, which potentially will degrade the lifespan and reliability of the capacitors in voltage source converters. This paper proposes a novel dc-capacitor current control...... method for a grid-side converter (GSC) to eliminate the negative impact of unbalanced grid voltage on the dc-capacitors. In this method, a dc-capacitor current control loop, where a negative-sequence resonant controller is used to increase the loop gain, is added to the conventional GSC current control...... loop. The rejection capability to the unbalanced grid voltage and the stability of the proposed control system are discussed. The second-order harmonic current in the dc capacitor as well as dc-voltage fluctuation is very well eliminated. Hence, the dc capacitors will be more reliable under unbalanced...

Density functional theory study of small X-doped Mg(n) (X = Fe, Co, Ni, n = 1-9) bimetallic clusters: equilibrium structures, stabilities, electronic and magnetic properties.

Science.gov (United States)

Kong, Fanjie; Hu, Yanfei

2014-03-01

The geometries, stabilities, and electronic and magnetic properties of Mg(n) X (X = Fe, Co, Ni, n = 1-9) clusters were investigated systematically within the framework of the gradient-corrected density functional theory. The results show that the Mg(n)Fe, Mg(n)Co, and Mg(n)Ni clusters have similar geometric structures and that the X atom in Mg(n)X clusters prefers to be endohedrally doped. The average atomic binding energies, fragmentation energies, second-order differences in energy, and HOMO-LUMO gaps show that Mg₄X (X = Fe, Co, Ni) clusters possess relatively high stability. Natural population analysis was performed and the results showed that the 3s and 4s electrons always transfer to the 3d and 4p orbitals in the bonding atoms, and that electrons also transfer from the Mg atoms to the doped atoms (Fe, Co, Ni). In addition, the spin magnetic moments were analyzed and compared. Several clusters, such as Mg₁,₂,₃,₄,₅,₆,₈,₉Fe, Mg₁,₂,₄,₅,₆,₈,₉Co, and Mg₁,₂,₅,₆,₇,₉Ni, present high magnetic moments (4 μ(B), 3 μ(B), and 2 μ(B), respectively).

AC Voltage Control of DC/DC Converters Based on Modular Multilevel Converters in Multi-Terminal High-Voltage Direct Current Transmission Systems

Directory of Open Access Journals (Sweden)

Rui Li

2016-12-01

Full Text Available The AC voltage control of a DC/DC converter based on the modular multilevel converter (MMC is considered under normal operation and during a local DC fault. By actively setting the AC voltage according to the two DC voltages of the DC/DC converter, the modulation index can be near unity, and the DC voltage is effectively utilized to output higher AC voltage. This significantly decreases submodule (SM capacitance and conduction losses of the DC/DC converter, yielding reduced capital cost, volume, and higher efficiency. Additionally, the AC voltage is limited in the controllable range of both the MMCs in the DC/DC converter; thus, over-modulation and uncontrolled currents are actively avoided. The AC voltage control of the DC/DC converter during local DC faults, i.e., standby operation, is also proposed, where only the MMC connected on the faulty cable is blocked, while the other MMC remains operational with zero AC voltage output. Thus, the capacitor voltages can be regulated at the rated value and the decrease of the SM capacitor voltages after the blocking of the DC/DC converter is avoided. Moreover, the fault can still be isolated as quickly as the conventional approach, where both MMCs are blocked and the DC/DC converter is not exposed to the risk of overcurrent. The proposed AC voltage control strategy is assessed in a three-terminal high-voltage direct current (HVDC system incorporating a DC/DC converter, and the simulation results confirm its feasibility.

First Implementation of a Two-Stage DC-DC Conversion Powering Scheme for the CMS Phase-2 Outer Tracker

CERN Document Server

Feld, Lutz Werner; Karpinski, Waclaw; Klein, Katja; Lipinski, Martin; Pauls, Alexander Josef; Preuten, Marius; Rauch, Max Philip; Wangelik, Frederik; Wlochal, Michael

2017-01-01

The 2S silicon strip modules for the CMS Phase-2 tracker upgrade will require two operating voltages. These will be provided via a two-step DC-DC conversion powering scheme, in which one DC-DC converter delivers 2.5\\,V while the second DC-DC converter receives 2.5\\,V at its input and converts it to 1.2\\,V. The DC-DC converters will be mounted on a flex PCB, the service hybrid, together with an opto-electrical converter module (VTRx+) and a serializer (LP-GBT). The service hybrid will be mounted directly on the 2S module. A prototype service hybrid has been developed and its performance has been evaluated, including radiative and conductive noise emissions, and efficiency. In addition system tests with a prototype module have been performed. In this report the service hybrid will be described and the test results will be summarized.

A suitable model plant for control of the set fuel cell-DC/DC converter

Energy Technology Data Exchange (ETDEWEB)

Andujar, J.M.; Segura, F.; Vasallo, M.J. [Departamento de Ingenieria Electronica, Sistemas Informaticos y Automatica, E.P.S. La Rabida, Universidad de Huelva, Ctra. Huelva - Palos de la Frontera, S/N, 21819 La Rabida - Palos de la Frontera Huelva (Spain)

2008-04-15

In this work a state and transfer function model of the set made up of a proton exchange membrane (PEM) fuel cell and a DC/DC converter is developed. The set is modelled as a plant controlled by the converter duty cycle. In addition to allow setting the plant operating point at any point of its characteristic curve (two interesting points are maximum efficiency and maximum power points), this approach also allows the connection of the fuel cell to other energy generation and storage devices, given that, as they all usually share a single DC bus, a thorough control of the interconnected devices is required. First, the state and transfer function models of the fuel cell and the converter are obtained. Then, both models are related in order to achieve the fuel cell+DC/DC converter set (plant) model. The results of the theoretical developments are validated by simulation on a real fuel cell model. (author)

Radial macrosegregation and dendrite clustering in directionally solidified Al-7Si and Al-19Cu alloys

Science.gov (United States)

Ghods, M.; Johnson, L.; Lauer, M.; Grugel, R. N.; Tewari, S. N.; Poirier, D. R.

2016-05-01

Hypoeutectic Al-7 wt% Si and Al-19 wt% Cu alloys were directionally solidified upward in a Bridgman furnace through a range of constant growth speeds and thermal gradients. Though processing is thermo-solutally stable, flow initiated by gravity-independent advection at, slightly leading, central dendrites moves rejected solute out ahead and across the advancing interface. Here any lagging dendrites are further suppressed which promotes a curved solid-liquid interface and the eventual dendrite "clustering" seen in transverse sections (dendrite "steepling" in longitudinal orientations) as well as extensive radial macrosegregation. Both aluminum alloys showed considerable macrosegregation at the low growth speeds (10 and 30 μm s-1) but not at higher speed (72 μm s-1). Distribution of the fraction eutectic-constituent on transverse sections was determined in order to quantitatively describe radial macrosegregation. The convective mechanisms leading to dendrite-steepling were elucidated with numerical simulations, and their results compared with the experimental observations.

Research of digital controlled DC/DC converter based on STC12C5410AD

Science.gov (United States)

Chen, Dan-Jiang; Jin, Xin; Xiao, Zhi-Hong

2010-02-01

In order to study application of digital control technology on DC/DC converter, principle of increment mode PID control algorithm was analyzed in the paper. Then, a SCM named STC12C5410AD was introduced with its internal resources and characteristics. The PID control algorithm can be implemented easily based on it. The output of PID control was used to change the value of a variable that is 255 times than duty cycle, and this reduced the error of calculation. The valid of the presented algorithm was verified by an experiment for a BUCK DC/DC converter. The experimental results indicated that output voltage of the BUCK converter is stable with low ripple.

On-grid and Off-grid Operation of Multi-Input Single-Output DC/DC Converter based Fuel Cell Generation System

Directory of Open Access Journals (Sweden)

Noroozian

2009-06-01

Full Text Available This paper presents the modeling and simulation of a proton exchange membrane fuel cell (PEMFC generation system for off-grid and on-grid operation and configuration. A fuel cell DG system consists of a fuel cell power plant, a DC/DC converter and a DC/AC inverter. The dynamic model for fuel cell array and its power electronic interfacing are presented also a multi-input single output (MISO DC/DC converter and its control scheme is proposed and analyzed. This DC/DC converter is capable of interfacing fuel cell arrays to the DC/AC inverter. Also the mathematical model of the inverter is obtained by using average technique. Then the novel control strategy of DC/AC inverter for different operating conditions is demonstrated. The simulation results show the effectiveness of the suggested control systems under both on-grid and off-grid operation modes.

RF-superimposed DC and pulsed DC sputtering for deposition of transparent conductive oxides

International Nuclear Information System (INIS)

Stowell, Michael; Mueller, Joachim; Ruske, Manfred; Lutz, Mark; Linz, Thomas

2007-01-01

Transparent conductive oxide films are widely used materials for electronic applications such as flat panel displays and solar cells. The superposition of DC and pulsed DC power by a certain fraction of RF power was applied to deposit indium tin oxide films. This technique allows an additional tuning of different parameters relevant to film growth, and yields high quality films even under kinetically limited conditions. A long-term stable RF/DC process could be realized by using different combinations of standard power supply components, which includes a fully reliable arc handling system for both the RF and DC generators. The effectiveness of the arc handling system is illustrated by the current and voltage behavior recorded for actual arcing events. The resistivity of indium tin oxide films is strongly influenced by the respective sputtering mode. The best resistivity values of 145-148 μΩ cm were obtained by RF-superimposed pulsed DC sputtering at a pulse frequency between 100 and 200 kHz and a substrate temperature as low as 140 deg. C. In addition, the films were extremely smooth with a surface roughness of 1-2.5 nm

The application of standardized control and interface circuits to three dc to dc power converters.

Science.gov (United States)

Yu, Y.; Biess, J. J.; Schoenfeld, A. D.; Lalli, V. R.

1973-01-01

Standardized control and interface circuits were applied to the three most commonly used dc to dc converters: the buck-boost converter, the series-switching buck regulator, and the pulse-modulated parallel inverter. The two-loop ASDTIC regulation control concept was implemented by using a common analog control signal processor and a novel digital control signal processor. This resulted in control circuit standardization and superior static and dynamic performance of the three dc-to-dc converters. Power components stress control, through active peak current limiting and recovery of switching losses, was applied to enhance reliability and converter efficiency.

Design of the DC-DC power stage of the capacitor charger for MAXIDISCAP power converters

CERN Document Server

Cravero, Jean-Marc

2013-01-01

This technical report presents the design of the DC-DC power stage of the capacitor charger for MAXIDISCAP power converters. The power stage is based on a half bridge series resonant converter in Discontinuous Conduction Mode (DCM). This simple and robust topology allows obtaining a current source behavior with a low switching losses power stage. The associated control stage is implemented using a commercial controller which has differenti nternal circuits that allows a high integration of the converter control system. The report presents the design and tuning criteria for the DC-DC converter, including the power stage and the control system.

X-ray cluster Abell 744

International Nuclear Information System (INIS)

Kurtz, M.J.; Huchra, J.P.; Beers, T.C.; Geller, M.J.; Gioia, I.M.

1985-01-01

X-ray and optical observations of the cluster of galaxies Abell 744 are presented. The X-ray flux (assuming H(0) = 100 km/s per Mpc) is about 9 x 10 to the 42nd erg/s. The X-ray source is extended, but shows no other structure. Photographic photometry (in Kron-Cousins R), calibrated by deep CCD frames, is presented for all galaxies brighter than 19th magnitude within 0.75 Mpc of the cluster center. The luminosity function is normal, and the isopleths show little evidence of substructure near the cluster center. The cluster has a dominant central galaxy, which is classified as a normal brightest-cluster elliptical on the basis of its luminosity profile. New redshifts were obtained for 26 galaxies in the vicinity of the cluster center; 20 appear to be cluster members. The spatial distribution of redshifts is peculiar; the dispersion within the 150 kpc core radius is much greater than outside. Abell 744 is similar to the nearby cluster Abell 1060. 31 references

Global transcriptional responses of Pseudomonas syringae DC3000 to changes in iron bioavailability in vitro

Directory of Open Access Journals (Sweden)

Rutzke Michael

2008-12-01

Full Text Available Abstract Background Pseudomonas syringae pv tomato DC3000 (DC3000 is a Gram-negative model plant pathogen that is found in a wide variety of environments. To survive in these diverse conditions it must sense and respond to various environmental cues. One micronutrient required for most forms of life is iron. Bioavailable iron has been shown to be an important global regulator for many bacteria where it not only regulates a wide variety of genes involved in general cell physiology but also virulence determinants. In this study we used microarrays to study differential gene regulation in DC3000 in response to changes in levels of cell-associated iron. Results DC3000 cultures were grown under highly controlled conditions and analyzed after the addition of iron citrate or sodium citrate to the media. In the cultures supplemented with iron, we found that cell-associated iron increased rapidly while culture densities were not significantly different over 4 hours when compared to cultures with sodium citrate added. Microarray analysis of samples taken from before and after the addition of either sodium citrate or iron citrate identified 386 differentially regulated genes with high statistical confidence. Differentially regulated genes were clustered based on expression patterns observed between comparison of samples taken at different time points and with different supplements. This analysis grouped genes associated with the same regulatory motifs and/or had similar putative or known function. Conclusion This study shows iron is rapidly taken up from the medium by iron-depleted DC3000 cultures and that bioavailable iron is a global cue for the expression of iron transport, storage, and known virulence factors in DC3000. Furthermore approximately 34% of the differentially regulated genes are associated with one of four regulatory motifs for Fur, PvdS, HrpL, or RpoD.

Analysis of DC/DC Converter Efficiency for Energy Storage System Based on Bidirectional Fuel Cells

DEFF Research Database (Denmark)

Pittini, Riccardo; Zhang, Zhe; Andersen, Michael A. E.

2013-01-01

interface to the grid. In power electronics, the converter efficiency is characterized at fixed operating voltage for various output power. This type of characterization is not suitable for fuel cells, since as the power from the fuel cell increases, the cell voltage decreases. This paper analyses how......Renewable energy sources are fluctuating depending on the availability of the energy source. For this reason, energy storage is becoming more important and bidirectional fuel cells represent an attractive technology. Fuel cells require highcurrent low-voltage dc-dc or dc-ac converters as power...... the fuel cell I-V characteristics influences the power electronics converter efficiency and their consequence on the overall system. A loaddependent efficiency curve is presented based on experimental results from a 6 kW dc-dc converter prototype including the most suitable control strategy which maximizes...

Design and Implementation of Digital Current Mode Controller for DC-DC Converters

DEFF Research Database (Denmark)

Taeed, Fazel

to be regulated by a closed-loop controller. The Peak Current Mode Control (PCMC) is one of the most promising control methods for dc-dc converters. It has been known for high bandwidth (speed), and inherent current protection. Increasing the controller bandwidth decreases the output filter size and cost. Analog...

Soft switching bidirectional DC-DC converter for ultracapacitor-batteries interface

International Nuclear Information System (INIS)

Adib, Ehsan; Farzanehfard, Hosein

2009-01-01

In this paper a new soft switching bidirectional DC-DC converter is introduced which can be applied as the interface circuit between ultracapacitors and batteries or fuel cells. All semiconductor devices in the proposed converter are soft switched while the control circuit remains PWM. Due to achieved soft switching condition, the energy conversion through the proposed converter is highly efficient. The proposed converter is analyzed and a prototype converter is implemented. The presented experimental results confirm the theoretical analysis.

Design and modelling of high gain DC-DC converters for fuel cell hybrid electric vehicles

Science.gov (United States)

Elangovan, D.; Karthigeyan, V.; Subhanu, B.; Ashwin, M.; Arunkumar, G.

2017-11-01

Transportation (Diesel and petrol internal combustion engine vehicles) approximately contributes to 25.5% of total CO2 emission. Thus diesel and petrol engine vehicles are the most dominant contributors of CO2 emission which leads global warming which causes climate change. The problem of CO2 emission and global warming can be reduced by focusing on renewable energy vehicles. Out of the available renewable energy sources fuel cell is the only source which has reasonable efficiency and can be used in vehicles. But the main disadvantage of fuel cell is its slow response time. So energy storage systems like batteries and super capacitors are used in parallel with the fuel cell. Fuel cell is used during steady state vehicle operation while during transient conditions like starting, acceleration and braking batteries and super capacitors can supply or absorb energy. In this paper a unidirectional fuel cell DC-DC converter and bidirectional energy storage system DC-DC converter is proposed, which can interface dc sources at different voltage levels to the dc bus and also it can independently control the power flow from each energy source to the dc bus and vice versa. The proposed converters are designed and simulated using PSIM version 9.1.1 and gate pulse pattern, input and output voltage waveforms of the converters for steady state operation are studied.

Modelling and Control Design of a Dual Buck-Boost AC/DC Converter Used in the DC Nano-Grid

DEFF Research Database (Denmark)

Wu, Weimin; Liu, Yuan; Wang, Houqing

2016-01-01

Due to widely used DC characterized loads and more distributed power generation sources, the DC Nano-grid becomes more and more popular and seen as an alternative to the AC-grid in future. For the safety considerations, the DC Nano-grid should provide reliable grounding for the residential loads...... like the low voltage AC power system. In this paper, a dual Buck-Boost AC/DC converter for use in the united grounding configuration based DC Nano-grid with three terminal outputs is proposed. It will be much easy to construct an efficient DC Nano-grid based on the existing low AC power system by using...

Magnetically integrated high step-up resonant DC-DC converter for distributed photovoltaic systems

DEFF Research Database (Denmark)

Vinnikov, Dmitri; Chub, Andrii; Liivik, Elizaveta

2017-01-01

In this paper magnetically integrated resonant single-switch quasi-Z-source DC-DC converter is evaluated as a candidate topology for the low-cost photovoltaic microconverter. The derivation of the topology and its basic operation principle are explained. Generalized design guidelines...

Drilling history core hole DC-4

International Nuclear Information System (INIS)

1978-12-01

Core hole DC-4 was completed at a depth of 3998 feet in December, 1978 by Boyles Brothers Drilling Company, Spokane, Washington, under subcontract to Fenix and Scission, Inc. The hole was cored for the US Department of Energy and the Rockwell Hanford Operations' Basalt Waste Isolation Program. Fenix and Sicsson, Inc. furnished the engineering, daily supervision of the cable tool and core drilling activities, and geological core logging for DC-4. Core hole DC-4 is located on the Hanford Site about 3 miles east of the Yakima Barricade and approximately 103 feet southwest of rotary hole DC-5, which was completed to 3990 feet in February, 1978. Hanford Site coordinates reported for hole DC-4 are north 49,385.62 feet and west 85,207.63 feet, and Washington State coordinates are north 454,468.73 feet and east 2,209,990.87 feet. No elevation survey is available for hole DC-4, but it is approximately 745 feet above mean sea level based upon the survey of hole DC-5, which has a reported elevation of 745.16 feet on the top of the 3-inch flange. The purpose of core hole DC-4 was to core drill vertically through the basalt and interbed units for stratigraphic depth determination and core collection, and to provide a borehole for hydrologic testing, cross-hole seismic shear, and pressure wave velocity studies with rotary hole DC-5. Hole DC-4 was drilled through the overburden into basalt bedrock by cable tool methods (0-623 feet) and continuously cored through the final interval (623 to 3998 feet).Core recovery was 95.8 percent of the total footage cored

DC-DC Type High-Frequency Link DC for Improved Power Quality of Cascaded Multilevel Inverter

Science.gov (United States)

Sadikin, Muhammad; Senjyu, Tomonobu; Yona, Atsushi

2013-06-01

Multilevel inverters are emerging as a new breed of power converter options for power system applications. Recent advances in power switching devices enabled the suitability of multilevel inverters for high voltage and high power applications because they are connecting several devices in series without the need of component matching. Usually, a transformerless battery energy storage system, based on a cascaded multilevel inverter, is used as a measure for voltage and frequency deviations. System can be reduced in size, weight, and cost of energy storage system. High-frequency link circuit topology is advantageous in realizing compact and light-weight power converters for uninterruptible power supply systems, new energy systems using photovoltaic-cells, fuel-cells and so on. This paper presents a DC-DC type high-frequency link DC (HFLDC) cascaded multilevel inverter. Each converter cell is implemented a control strategy for two H-bridge inverters that are controlled with the same multicarrier pulse width modulation (PWM) technique. The proposed cascaded multilevel inverter generates lower voltage total harmonic distortion (THD) in comparison with conventional cascaded multilevel inverter. Digital simulations are carried out using PSCAD/EMTDC to validate the performance of the proposed cascaded multilevel inverter.

Wide Temperature Range DC-DC Boost Converters for Command/Control/Drive Electronics, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — We shall develop wide temperature range DC-DC boost converters that can be fabricated using commercial CMOS foundries. The boost converters will increase the low...

DC Microgrids—Part II

DEFF Research Database (Denmark)

Dragicevic, Tomislav; Lu, Xiaonan; Quintero, Juan Carlos Vasquez

2016-01-01

distribution applications such as traction, telecom, vehicular and distributed power systems can be classified under DC MG framework and ongoing development and expansion of the field is largely influenced by concepts used over there. This paper aims firstly to shed light on the practical design aspects of DC...... MG technology concerning typical power hardware topologies and their suitability for different emerging smart grid applications. Then, an overview of the state of the art in DC MG protection and grounding is provided. Owing to the fact that there is no zero current crossing, an arc that appears upon...

Selection of DC/DC converter for offshore wind farms with MVDC power collection

DEFF Research Database (Denmark)

Dincan, Catalin Gabriel; Kjær, Philip Carne; Chen, Yu-Hsing

2017-01-01

Four DC/DC converters are analyzed and compared with respects to availability, efficiency, ratings, repair costs and power density. Intended application is offshore wind farms with MVDC power collection. The selected topology is a new series resonant converter, which offers 99% efficiency across...

Integrated Three-Port DC-DC Converter for Photovoltaic (PV) Battery Stand-alone Systems

DEFF Research Database (Denmark)

Ouyang, Ziwei; Andersen, Michael A. E.

2016-01-01

of solar energy. Moreover, a novel transformer configuration enables variable turns ratio controlled by the phase between the two current excitations subjected to the primary windings, allowing a wider input/output range. 1 kW experimental prototype has been built to demonstrate a wellmanaged power flow......Several power sources such as PV solar arrays and battery are often used to manage the power flow for a photovoltaic (PV) based stand-alone power system due to the fluctuation nature of solar energy resource, and deliver a continuous power to the users in an appropriate form. Traditionally, three...... different single-input single-output (SISO) dc/dc converters would have been used. To reduce the cost and improve the power density of the system, an integrated three-port isolated dc/dc converter is proposed in this paper. It can realize all functions of the energy delivery due to the fluctuation nature...

Integrating DC/DC Conversion with Possible Reconfiguration within Submodule Solar Photovoltaic Systems

Science.gov (United States)

Huang, Peter Jen-Hung

This research first proposes a method to merge photovoltaic (PV) cells or PV panels within the internal components DC-DC converters. The purpose of this merged structure is to reconfigure the PV modules between series and parallel connections using high switching frequencies (hundreds of kHz). This leads to multi-levels of voltages and currents that become applied to the output filter of the converter. Further, this research introduces a concept of a switching cell that utilizes the reconfiguration of series and parallel connections in DC-DC converters. The switching occurs at high switching frequency and the switches can be integrated to be within the solar panels or in between the solar cells. The concept is generalized and applied to basic buck and boost topologies. As examples of the new types of converters: reconfigurable PV-buck and PV-boost converter topologies are presented. It is also possible to create other reconfigurable power converters: non-isolated and isolated topologies. Analysis, simulation and experimental verification for the reconfigurable PV-buck and PV-boost converters are presented extensively to illustrate proof of concept. Benefits and drawbacks of the new approach are discussed. The second part of this research proposes to utilize the internal solar cell capacitance and internal solar module wire parasitic inductances to replace the input capacitor and filter inductor in boost derived DC-DC converters for energy harvesting applications. High switching frequency (MHz) hard switched and resonant boost converters are proposed. Their analysis, simulation and experimental prototypes are presented. A specific proof-of-concept application is especially tested for foldable PV panels, which are known for their high internal wire inductance. The experimental converters successfully boost solar module voltage without adding any external input capacitance or filter inductor. Benefits and drawbacks of new proposed PV submodule integrated boost

Soft switching bidirectional DC-DC converter for ultracapacitor-batteries interface

Energy Technology Data Exchange (ETDEWEB)

Adib, Ehsan; Farzanehfard, Hosein [Dept. of Electrical and Computer Engineering, Isfahan Univ. of Technology (Iran)

2009-12-15

In this paper a new soft switching bidirectional DC-DC converter is introduced which can be applied as the interface circuit between ultracapacitors and batteries or fuel cells. All semiconductor devices in the proposed converter are soft switched while the control circuit remains PWM. Due to achieved soft switching condition, the energy conversion through the proposed converter is highly efficient. The proposed converter is analyzed and a prototype converter is implemented. The presented experimental results confirm the theoretical analysis. (author)

Retrospective evaluation of early and aggressive decompressive craniectomy (DC) for severe head injury. Was that DC necessary?

International Nuclear Information System (INIS)

Hagihara, Yasushi; Ueno, Masato; Mizushima, Yasuaki; Matsuoka, Tetsuya

2011-01-01

Recently, decompressive craniectomy (DC) for refractory intracranial hypertension (IH) has been widely reevaluated, and many researchers support the advantages of early and aggressive DC in the management of severe head trauma. We too applied DC in the early stages of IH, and confirmed its favorable results compared to those of the standard treatment. In patients with evacuate masses (EM), DC was determined based on the intraoperative condition of the brain parenchyma; in those without EM, intracranial pressure (ICP) ≥30 mmHg was considered the criterion for DC. However, in some cases, the expected brain edema (BE) was absent after DC, and DC seemed unnecessary on retrospection. Here, the effectiveness of DC performed at our hospital and its predictive factors were investigated. Of the 26 DCs performed in the past 3.5 years, 9 were ineffective because the expected BEs were absent on postoperative computed tomography. In those 9 cases, the Glasgow coma scale (GCS) scores and D-dimer of fibrinogen degradation product (FDP-DD) were significantly higher and lower, respectively, than those of the control group. Patients with EM showed similar trends regarding the GCS score and FDP-DD, both of which are probable indicators of BE. In patients without EM, the GCS score and FDP-DD were normal, but their base excess at admission was significantly low with increased ICP, requiring DC. GCS score and FDP-DD may represent the extent of mechanically damaged brain, and this may explain their relation with DC effectiveness in patients with EM. In patients without EM and with mild brain damage, base excess that reflects the respiratory or circulatory disorder should be the predictor for BE. (author)

Infrared spectroscopy of ionic clusters

International Nuclear Information System (INIS)

Price, J.M.

1990-11-01

This thesis describes new experiments wherein the infrared vibrational predissociation spectra of a number of mass-selected ionic cluster systems have been obtained and analyzed in the 2600 to 4000 cm -1 region. The species studied include: the hydrated hydronium ions, H 3 O + (H 2 O) 3 -10 , ammoniated ammonium ions, NH 4 + (NH 3 ) 1 -10 and cluster ions involving both water and ammonia around an ammonium ion core, (mixed clusters) NH 4 + (NH 3 ) n (H 2 O) m (n+m=4). In each case, the spectra reveal well resolved structures that can be assigned to transitions arising from the vibrational motions of both the ion core of the clusters and the surrounding neutral solvent molecules. 154 refs., 19 figs., 8 tabs

Exploration of Charge Recycling DC-DC Conversion Using a Switched Capacitor Regulator

Directory of Open Access Journals (Sweden)

Mircea R. Stan

2013-07-01

Full Text Available The increasing popularity of DVFS (dynamic voltage frequency scaling schemes for portable low power applications demands highly efficient on-chip DC-DC converters. The primary aim of this work is to enable increased efficiency of on-chip DC-DC conversion for near-threshold operation of multicore chips. The idea is to supply nominal (high off-chip voltage to the cores which are then “voltage-stacked” to generate the near-threshold (low voltages based on Kirchhoff’s voltage law through charge recycling. However, the effectiveness of this implicit down-conversion is affected by the current imbalance among the cores. The paper presents a design methodology and optimization strategy for highly efficient charge recycling on-chip regulation using a push-pull switched capacitor (SC circuit. A dual-boundary hysteretic feedback control circuit has been designed for stacked loads. A stacked-voltage domain with its self-regulation capability combined with a SC converter has shown average efficiency of 78%–93% for 2:1 down-conversion with ILoad (max of 200 mA and workload imbalance varying from 0–100%.

High-Efficiency High Step-Up DC-DC Converter with Dual Coupled Inductors for Grid-Connected Photovoltaic Systems

DEFF Research Database (Denmark)

Forouzesh, Mojtaba; Shen, Yanfeng; Siwakoti, Yam Prasad

2018-01-01

with a common ground connection of the input and output make the proposed topology a proper candidate for a transformer-less grid connected photovoltaic systems. The operating performance, analysis and mathematical derivations of the proposed dc-dc converter have been demonstrated in the paper. Moreover......This paper introduces a non-isolated high step-up dc-dc converter with dual coupled inductors suitable for distributed generation applications. By implementing an input parallel connection, the proposed dc-dc structure inherits shared input current with low ripple, which also requires small...... capacitive filter at its input. Moreover, this topology can reach high voltage gain by using dual coupled inductors in series connection at the output stage. The proposed converter uses active clamp circuits with a shared clamp capacitor for the main switches. In addition to the active clamp circuit...

Design and Implementation of Anti-windup PI Control on DC-DC Bidirectional Converter for Hybrid Vehicle Applications

Directory of Open Access Journals (Sweden)

Muh. Zakiyullah Romdlony

2012-07-01

Full Text Available Well-regulated DC bus voltage is the important point to guarantee the power demand in hybrid vehicle applications. Voltage regulation can be achieved with control method that build switching signal on DC-DC converter. This paper describes design and small scale experimental results of bus voltage regulation control of the DC-DC bidirectional converter with battery and supercapacitor as energy source. The control system consists of two control loops, the outer loop that get DC bus voltage feedback using PI anti-windup back calculation control method. This outer loop will generate a reference current for the inner loop that implement hysteresis control. The inner control loop will compare that reference curent with the source current obtained from the current sensor. Simulation and experimental results show that bus voltage is well-regulated under the load changes with 1% voltage ripple.

Light-weight DC to very high voltage DC converter

Energy Technology Data Exchange (ETDEWEB)

Druce, Robert L. (Union City, CA); Kirbie, Hugh C. (Dublin, CA); Newton, Mark A. (Livermore, CA)

1998-01-01

A DC-DC converter capable of generating outputs of 100 KV without a transformer comprises a silicon opening switch (SOS) diode connected to allow a charging current from a capacitor to flow into an inductor. When a specified amount of charge has flowed through the SOS diode, it opens up abruptly; and the consequential collapsing field of the inductor causes a voltage and current reversal that is steered into a load capacitor by an output diode. A switch across the series combination of the capacitor, inductor, and SOS diode closes to periodically reset the SOS diode by inducing a forward-biased current.

Current Mode Control for LLC Series Resonant DC-to-DC Converters

OpenAIRE

Jinhaeng Jang; Syam Kumar Pidaparthy; Byungcho Choi

2015-01-01

Conventional voltage mode control only offers limited performance for LLC series resonant DC-to-DC converters experiencing wide variations in operational conditions. When the existing voltage mode control is employed, the closed-loop performance of the converter is directly affected by unavoidable changes in power stage dynamics. Thus, a specific control design optimized at one particular operating point could become unacceptable when the operational condition is varied. This paper presents a...

Floating high step-down stacked dc-dc converter based on buck-boost cells

NARCIS (Netherlands)

Tibola, G.; Duarte, J.L.; Blinov, A.

2015-01-01

In some high power dc-dc applications, where high voltage is present, a converter with high step-down ratio is required in order to provide an isolated low power auxiliary supply. This requirement represents a challenge and many topologies are currently being researched. The analysis of a

UNJUK KERJA PENGUBAH TEGANGAN DC-DC TOPOLOGI BOOST DENGAN NILAI INDUKTANSI DAN KAPASITANSI YANG DIOPTIMASI PADA KEADAAN TRANSIEN

Directory of Open Access Journals (Sweden)

I Wayan Arta Wijaya

2009-05-01

Full Text Available Pengubah daya DC-DC topologi boost dapat menghasilkan tegangan yang lebih tinggi dari tegangan input dengan riak (ripple yang kecil dan efisiensi yang cukup tinggi. Nilai dari sebuah induktansi dan kapasitansi dari pengubah daya DC-DC dengan menggunakan topologi boost dioptimalkan menggunakan analisa transien. Fungsi ini diatur berdasarkan pada analisa dari pengubah daya selama kondisi transien. Nilai induktansi dan kapasitansi yang telah dioptimalkan dengan perhitungan dibandingkan dalam simulasi pada pengubah daya DC-DC dan hasilnya akan dibuktikan dengan menggunakan hasil percobaan. Nilai optimal untuk kapasitor dan induktor pada frekuensi 666,7 Hz, siklus kerja (duty cycle 66,7 %, resistansi output 36 Ώ dan tegangan input 12 volt adalah 1038 μF dan 11,9 mH

Rhesus macaque and chimpanzee DC-SIGN act as HIV/SIV gp120 trans-receptors, similar to human DC-SIGN

NARCIS (Netherlands)

Geijtenbeek, T. B.; Koopman, G.; van Duijnhoven, G. C.; van Vliet, S. J.; van Schijndel, A. C.; Engering, A.; Heeney, J. L.; van Kooyk, Y.

2001-01-01

Dendritic cells (DC) have been implicated in the pathogenesis of both human and simian immunodeficiency viruses (HIV and SIV, respectively). The DC-specific HIV-1 trans-receptor DC-SIGN is thought to be essential for viral dissemination by DC. Abundant expression in lymphoid tissues also implies a

The Chaotic-Based Control of Three-Port Isolated Bidirectional DC/DC Converters for Electric and Hybrid Vehicles

Directory of Open Access Journals (Sweden)

Zheng Wang

2016-01-01

Full Text Available Three-port isolated (TPI bidirectional DC/DC converters have three energy ports and offer advantages of large voltage gain, galvanic isolation ability and high power density. For this reason this kind of converters are suitable to connect different energy sources and loads in electric and hybrid vehicles. The purpose of this paper is to propose chaotic modulation and the related control scheme for TPI bidirectional DC/DC converters, in such a way that the switching harmonic peaks can be suppressed in spectrum and the conducted electromagnetic interference (EMI is reduced. Two chaotic modulation strategies, namely the continuously chaotic modulation and the discretely chaotic modulation are presented. These two chaotic modulation strategies are applied for TPI bidirectional DC/DC converters with shifted-phase angle based control and phase-shifted PWM control. Both simulation and experiments are given to verify the validity of the proposed chaotic modulation-based control schemes.

Interstellar Extinction in 20 Open Star Clusters

Science.gov (United States)

Rangwal, Geeta; Yadav, R. K. S.; Durgapal, Alok K.; Bisht, D.

2017-12-01

The interstellar extinction law in 20 open star clusters namely, Berkeley 7, Collinder 69, Hogg 10, NGC 2362, Czernik 43, NGC 6530, NGC 6871, Bochum 10, Haffner 18, IC 4996, NGC 2384, NGC 6193, NGC 6618, NGC 7160, Collinder 232, Haffner 19, NGC 2401, NGC 6231, NGC 6823, and NGC 7380 have been studied in the optical and near-IR wavelength ranges. The difference between maximum and minimum values of E(B - V) indicates the presence of non-uniform extinction in all the clusters except Collinder 69, NGC 2362, and NGC 2384. The colour excess ratios are consistent with a normal extinction law for the clusters NGC 6823, Haffner 18, Haffner 19, NGC 7160, NGC 6193, NGC 2401, NGC 2384, NGC 6871, NGC 7380, Berkeley 7, Collinder 69, and IC 4996. We have found that the differential colour-excess ΔE(B - V), which may be due to the occurrence of dust and gas inside the clusters, decreases with the age of the clusters. A spatial variation of colour excess is found in NGC 6193 in the sense that it decreases from east to west in the cluster region. For the clusters Berkeley 7, NGC 7380, and NGC 6871, a dependence of colour excess E(B - V) with spectral class and luminosity is observed. Eight stars in Collinder 232, four stars in NGC 6530, and one star in NGC 6231 have excess flux in near-IR. This indicates that these stars may have circumstellar material around them.

A Markovian Approach Applied to Reliability Modeling of Bidirectional DC-DC Converters Used in PHEVs and Smart Grids

Directory of Open Access Journals (Sweden)

M. Khalilzadeh

2016-12-01

Full Text Available In this paper, a stochastic approach is proposed for reliability assessment of bidirectional DC-DC converters, including the fault-tolerant ones. This type of converters can be used in a smart DC grid, feeding DC loads such as home appliances and plug-in hybrid electric vehicles (PHEVs. The reliability of bidirectional DC-DC converters is of such an importance, due to the key role of the expected increasingly utilization of DC grids in modern Smart Grid. Markov processes are suggested for reliability modeling and consequently calculating the expected effective lifetime of bidirectional converters. A three-leg bidirectional interleaved converter using data of Toyota Prius 2012 hybrid electric vehicle is used as a case study. Besides, the influence of environment and ambient temperature on converter lifetime is studied. The impact of modeling the reliability of the converter and adding reliability constraints on the technical design procedure of the converter is also investigated. In order to investigate the effect of leg increase on the lifetime of the converter, single leg to five-leg interleave DC-DC converters are studied considering economical aspect and the results are extrapolated for six and seven-leg converters. The proposed method could be generalized so that the number of legs and input and output capacitors could be an arbitrary number.

PI and Fuzzy Control Strategies for High Voltage Output DC-DC Boost Power Converter - Hardware Implementation and Analysis

DEFF Research Database (Denmark)

Padmanaban, Sanjeevi Kumar; Blaabjerg, Frede; Siano, Pierluigi

2016-01-01

This paper presents the control strategies by Proportional-Integral (P-I) and Fuzzy Logic (FL) for a DC-DC boost power converter for high output voltage configuration. Standard DC-DC converters are traditionally used for high voltage direct current (HVDC) power transmission systems. But, lack its...... converter with inbuilt voltage-lift technique and overcome the aforementioned deficiencies. Further, the control strategy is adapted based on proportional-integral (P-I) and fuzzy logic, closed-loop controller to regulate the outputs and ensure the performances. Complete hardware prototype of EHV converter...... performances in terms of efficiency, reduced transfer gain and increased cost with sensor units. Moreover, the internal self-parasitic components reduce the output voltage and efficiency of classical high voltage converters (HVC). This investigation focused on extra high-voltage (EHV) DC-DC boost power...

A Novel Quasi-SEPIC High-Voltage Boost DC-DC Converter

DEFF Research Database (Denmark)

Siwakoti, Yam Prasad; N. Soltani, Mohsen; Blaabjerg, Frede

2017-01-01

This paper proposes a modified coupled-inductor SEPIC dc-dc converter for low power and high voltage gain applications such as for piezoelectric drive systems. The converter uses the same components as of SEPIC converter with an additional diode. Compared to conventional topologies with similar...... voltage gain expression, the proposed topology uses less components to achieve same or even higher voltage gain. This helps to design a very compact and light weight converter with higher power density at lower cost. Due to brevity, the principle of operation, theoretical analysis and comparison supported...

Properties of DLC coatings deposited by dc and dc with superimposed pulsed vacuum arc

International Nuclear Information System (INIS)

Zavaleyev, V.; Walkowicz, J.; Aksyonov, D.S.; Luchaninov, A.A.; Reshetnyak, E.N.; Strel'nitskij, V.E.

2014-01-01

Comparative studies of the structure, mechanical and tribological properties of DLC coatings deposited in DC and DC with superimposed high current pulse modes of operation vacuum-arc plasma source with the graphite cathode are presented. Imposition the pulses of high current on DC vacuum-arc discharge allows both increase the deposition rate of DLC coating and reduce the residual compressive stress in the coatings what promotes substantial improvement the adhesion to the substrate. Effect of vacuum arc plasma filtration with Venetian blind filter on the deposition rate and tribological characteristics of the coatings analyzed.

Light-weight DC to very high voltage DC converter

Science.gov (United States)

Druce, R.L.; Kirbie, H.C.; Newton, M.A.

1998-06-30

A DC-DC converter capable of generating outputs of 100 KV without a transformer comprises a silicon opening switch (SOS) diode connected to allow a charging current from a capacitor to flow into an inductor. When a specified amount of charge has flowed through the SOS diode, it opens up abruptly; and the consequential collapsing field of the inductor causes a voltage and current reversal that is steered into a load capacitor by an output diode. A switch across the series combination of the capacitor, inductor, and SOS diode closes to periodically reset the SOS diode by inducing a forward-biased current. 1 fig.

The 25 kW resonant dc/dc power converter

Science.gov (United States)

Robson, R. R.

1983-01-01

The feasibility of processing 25-kW of power with a single, transistorized, series resonant converter stage was demonstrated by the successful design, development, fabrication, and testing of such a device which employs four Westinghouse D7ST transistors in a full-bridge configuration and operates from a 250-to-350 Vdc input bus. The unit has an overall worst-case efficiency of 93.5% at its full rated output of 1000 V and 25 A dc. A solid-state dc input circuit breaker and output-transient-current limiters are included in and integrated into the design. Full circuit details of the converter are presented along with the test data.

DC grid for home applications

Science.gov (United States)

Elangovan, D.; Archana, R.; Jayadeep, V. J.; Nithin, M.; Arunkumar, G.

2017-11-01

More than fifty percent Indian population do not have access to electricity in daily lives. The distance between the power generating stations and the distribution centers forms one of the main reasons for lack of electrification in rural and remote areas. Here lies the importance of decentralization of power generation through renewable energy resources. In the present world, electricity is predominantly powered by alternating current, but most day to day devices like LED lamps, computers and electrical vehicles, all run on DC power. By directly supplying DC to these loads, the number of power conversion stages was reduced, and overall system efficiency increases. Replacing existing AC network with DC is a humongous task, but with power electronic techniques, this project intends to implement DC grid at a household level in remote and rural areas. Proposed work was designed and simulated successfully for various loads amounting to 250 W through appropriate power electronic convertors. Maximum utilization of the renewable sources for domestic and commercial application was achieved with the proposed DC topology.

Dc-SQUID sensor system for multichannel neuromagnetometry

Energy Technology Data Exchange (ETDEWEB)

Houwman, E.P.; Veldhuis, D.; Flokstra, ter Brake, H.J.M.; Jaszczuk, W.; Rogalla, H. (Univ. of Twente, Faculty of Applied Physics, P.O. Box 217, 7500 AE Enschede (NL)); Martinez, A. (Universidad de Zaragoza, E.T.S.I.I. Maria Zambrano 50, 50015 Zaragoza (ES))

1991-03-01

This paper reports on various DC-SQUID sensor configurations developed for use in the authors' 19-channel neuromagetometer. Apart from the standard type, resistively and indictively shunted SQUIDs were made, allowing for a large screening factor {beta} ({gt}1). In this way signal coupling from the pick-up coil to the SQUID is facilitated and capactive coupling between the input coil and the SQUID washer can be decreased. The number of turns of the input coil is decreased further by allowing for an inductance mismatch in the input circuit. Although theoretically both measures give rise to an increased field noise of the sensor, they may lead to a reduction of the excess noise and the noise balance may become positive.

V1.42In1.83Mo15Se19

Directory of Open Access Journals (Sweden)

Michel Potel

2010-10-01

Full Text Available The structure of the title compound, vanadium indium pentadecamolybdenum nonadecaselenide, V1.42In1.83Mo15Se19, is isotypic with In2.9Mo15Se19 [Grüttner et al. (1979. Acta Cryst. B35, 285–292]. It is characterized by two cluster units Mo6Sei8Sea6 and Mo9Sei11Sea6 (where i represents inner and a apical atoms that are present in a 1:1 ratio. The cluster units are centered at Wyckoff positions 2b and 2c and have point-group symmetry overline{3} and overline{6}, respectively. The clusters are interconnected through additional Mo—Se bonds. In the title compound, the V3+ cations replace the trivalent indium atoms present in In2.9Mo15Se19, and a deficiency is observed on the monovalent indium site. One Mo, one Se and the V atom are situated on mirror planes, and two other Se atoms and the In atom are situated on threefold rotation axes.

Static and Dynamic Characteristics of DC-DC Converter Using a Digital Filter

Science.gov (United States)

Kurokawa, Fujio; Okamatsu, Masashi

This paper presents the regulation and dynamic characteristics of the dc-dc converter with digital PID control, the minimum phase FIR filter or the IIR filter, and then the design criterion to improve the dynamic characteristics is discussed. As a result, it is clarified that the DC-DC converter using the IIR filter method has superior performance characteristics. The regulation range is within 1.3%, the undershoot against the step change of the load is less than 2% and the transient time is less than 0.4ms with the IIR filter method. In this case, the switching frequency is 100kHz and the step change of the load R is from 50 Ω to 10 Ω. Further, the superior characteristics are obtained when the first gain, the second gain and the second cut-off frequency are relatively large, and the first cut-off frequency and the passing frequency are relatively low. Moreover, it is important that the gain strongly decreases at the second cut-off frequency because the upper band pass frequency range must be always less than half of the sampling frequency based on the sampling theory.

Radio emission of Abell Clusters in the GB region

International Nuclear Information System (INIS)

Michalec, A.

1977-01-01

In the GB survey region (Maslowski 1972) there are 102 Abell Clusters (Abell 1958) 31 of them coincide with the positions of Gb radio sources. The number of random coincidences was estimated from a Poisson distribution. For 19 cluster from this group, the observations at 2695 MHz were made with the same instrument. The clusters' redshifts were estimated. On the basis of this material, an analysis of the luminosity function for these cluster was carried out. (author)

DC-Compensated Current Transformer †

Science.gov (United States)

Ripka, Pavel; Draxler, Karel; Styblíková, Renata

2016-01-01

Instrument current transformers (CTs) measure AC currents. The DC component in the measured current can saturate the transformer and cause gross error. We use fluxgate detection and digital feedback compensation of the DC flux to suppress the overall error to 0.15%. This concept can be used not only for high-end CTs with a nanocrystalline core, but it also works for low-cost CTs with FeSi cores. The method described here allows simultaneous measurements of the DC current component. PMID:26805830

Reliability study of high gain DC-DC converters based on RRPP I-IIA ...

Indian Academy of Sciences (India)

J DIVYA NAVAMANI

2018-05-10

May 10, 2018 ... Energy Storage Modules (ESM), Propulsion Motor Mod- ules (PMM) and ... All Electric Ship (AES) is the best way to power all the loads in the ship ... also used to derive quadratic step down DC-DC converters. [6]. The attractive ...... Exhibition on Ecological Vehicles and Renewable Energies,. TamilNadu ...

Influence of DC arc jets on flow fields analyzed by an integrated numerical model for a DC-RF hybrid plasma

International Nuclear Information System (INIS)

Seo, Jun Ho; Park, Jin Myung; Hong, Sang Hee

2008-01-01

The influence of DC arc jets on the flow fields in a hybrid plasma torch is numerically analyzed by an integrated direct current-radio frequency (DC-RF) plasma model based on magneto-hydrodynamic formulations. The calculated results reveal that the increase in DC arc gas flow rate raises the axial flow velocity along the central column of the DC-RF hybrid plasma together with the enhanced backflow streams in the peripheral wall region. The temperature profiles on the torch exit plane are little affected due to the reheating process of the central column by the combined RF plasma. Accordingly, the exit enthalpy emitted from the DC-RF hybrid torch can be concentrated to the central column of the plasma and controlled by adjusting the DC arc gas flow rate. The swirl in the sheath gas flow turns out to have the opposite effect on the DC arc gas flow rate. The swirling motion of the sheath gas can reduce the back flows near the induction tube wall as well as the axial velocities in the central column of the plasma. Accordingly, the swirl in the sheath gas flow can be used for the functional operation of the DC-RF hybrid plasma along with the DC arc gas flow rate to suppress the back flows at the wall region and to reduce the excessive interactions between the DC arc jet and the ambient RF plasmas. The effects of DC input current on the flow fields of hybrid plasma are similar to those of the DC arc gas flow rate, but the axial velocities for the higher current relatively quickly decay along the centerline. This is in contrast to the increase in the axial velocity remaining in proportion to the increase in the DC arc gas flow rate all the way up to the exit of the DC-RF hybrid plasma. Accordingly, the present integrated numerical analysis suggests that the hybrid plasma field profiles and the entrainment of ambient air from the torch exit are controllable by adjusting the DC arc gas flow rate, the DC input current and swirl in the sheath gas flow taking advantage of

Dilation and Curettage (D&C)

Science.gov (United States)

... For Patients About ACOG Dilation and Curettage (D&C) Home For Patients Search FAQs Dilation and Curettage ( ... February 2016 PDF Format Dilation and Curettage (D&C) Special Procedures What is dilation and curettage (D& ...

Ultrahigh-density trench cpacitors in silicon and their application to integrated DC-DC conversion

NARCIS (Netherlands)

Roozeboom, F.; Bergveld, H.J.; Nowak, K.; Le Cornec, F.; Guiraud, L.; Bunel, C.; Iochem, S.; Ferreira, J.; Ledain, S.; Pieraerts, E.; Pommier, M.

2009-01-01

This paper addresses silicon-based integration of passive components applied to 3D integration with dies of other technologies within one package. Particularly, the development of high-density trench capacitors has enabled the realization of small-formfactor DC-DC converters. As illustration, an

Spectral shaping of a randomized PWM DC-DC converter using maximum entropy probability distributions

CSIR Research Space (South Africa)

Dove, Albert

2017-01-01

Full Text Available maintaining constraints in a DC-DC converter is investigated. A probability distribution whose aim is to ensure maximal harmonic spreading and yet mainaint constraints is presented. The PDFs are determined from a direct application of the method of Maximum...

Programmable dc motor controller

Science.gov (United States)

Hopwood, J. E.

1982-11-01

A portable programmable dc motor controller, with features not available on commercial instruments was developed for controlling fixtures during welding processes. The controller can be used to drive any dc motor having tachometer feedback and motor requirements not exceeding 30 volts, 3 amperes. Among the controller's features are delayed start time, upslope time, speed, and downslope time.

Hybrid Non-Isolated and Non Inverting Nx Interleaved DC-DC Multilevel Boost Converter for Renewable Energy Applications

DEFF Research Database (Denmark)

Bhaskar, Mahajan Sagar; Kulkarni, Rishi M.; Padmanaban, Sanjeevi Kumar

2016-01-01

In this paper hybrid non isolated/ non inverting Nx interleaved DC-DC multilevel Boost Converter for renewable energy applications is presented. The presented hybrid topology is derived from the conventional interleaved converter and the Nx Multilevel boost converter. In renewable energy...... applications, generated energy cannot be directly used at application end. In most of the cases it needs to be stepped up with DC-DC converter at operating voltage levels as per the requirement of the application. Though conventional boost converter can theoretically be used for this purpose, but obtaining...

A comprehensive analysis and hardware implementation of control strategies for high output voltage DC-DC boost power converter

OpenAIRE

Padmanaban, Sanjeevikumar; Grandi, Gabriele; Blaabjerg, Frede; Wheeler, Patrick; Siano, Pierluigi; Hammami, Manel

2017-01-01

Classical DC-DC converters used in high voltage direct current (HVDC) power transmission systems, lack in terms of efficiency, reduced transfer gain and increased cost with sensor (voltage/current) numbers. Besides, the internal self-parasitic behavior of the power components reduces the output voltage and efficiency of classical HV converters. This paper deals with extra high-voltage (EHV) dc-dc boost converter by the application of voltage-lift technique to overcome the aforementioned defic...

Response of cluster headache to psilocybin and LSD.

Science.gov (United States)

Sewell, R Andrew; Halpern, John H; Pope, Harrison G

2006-06-27

The authors interviewed 53 cluster headache patients who had used psilocybin or lysergic acid diethylamide (LSD) to treat their condition. Twenty-two of 26 psilocybin users reported that psilocybin aborted attacks; 25 of 48 psilocybin users and 7 of 8 LSD users reported cluster period termination; 18 of 19 psilocybin users and 4 of 5 LSD users reported remission period extension. Research on the effects of psilocybin and LSD on cluster headache may be warranted.

Direct switching control of DC-DC power electronic converters using hybrid system theory

Energy Technology Data Exchange (ETDEWEB)

Zhao, J.; Lin, F. [Wayne State Univ., Detroit, MI (United States). Dept. of Electrical and Computer Engineering; Wang, C. [Wayne State Univ., Detroit, MI (United States). Dept. of Electrical and Computer Engineering; Wayne State Univ., Detroit, MI (United States). Div. of Engineering Technology

2010-07-01

A direct switching control (DSC) scheme for power electronics converters was described. The system was designed for use in both traditional and renewable energy applications as well as in electric drive vehicles. The proposed control scheme was based on a detailed hybrid system converter model that used model predictive control (MPC), piecewise affine (PWA) approximations and constrained optimal control methods. A DC-DC converter was modelled as a hybrid machine. Switching among different modes of the DC-DC converter were modelled as discrete events controlled by the hybrid controller. The modelling scheme was applied to a Buck converter. The DSC was used to control the switch of the power converter based on a hybrid machine model. Results of the study showed that the method can be used to regulate output voltage and inductor currents. The method also provides fast transient responses and effectively regulates both currents and voltage. The controller can be used to provide immediate responses to dynamic disturbances and output voltage fluctuations. 23 refs., 7 figs.

Informational model verification of ZVS Buck quasi-resonant DC-DC converter

Science.gov (United States)

Vakovsky, Dimiter; Hinov, Nikolay

2016-12-01

The aim of the paper is to create a polymorphic informational model of a ZVS Buck quasi-resonant DC-DC converter for the modeling purposes of the object. For the creation of the model is applied flexible open standards for setting, storing, publishing and exchange of data in distributed information environment. The created model is useful for creation of many and different by type variants with different configuration of the composing elements and different inner model of the examined object.

Switched capacitor DC-DC converter with switch conductance modulation and Pesudo-fixed frequency control

DEFF Research Database (Denmark)

Larsen, Dennis Øland; Vinter, Martin; Jørgensen, Ivan Harald Holger

A switched capacitor dc-dc converter with frequency-planned control is presented. By splitting the output stage switches in eight segments the output voltage can be regulated with a combination of switching frequency and switch conductance. This allows for switching at predetermined frequencies, 31...

A Novel Dual-input Isolated Current-Fed DC-DC Converter for Renewable Energy System

DEFF Research Database (Denmark)

Zhang, Zhe; Thomsen, Ole Cornelius; Andersen, Michael A. E.

2010-01-01

In this paper, a novel isolated current-fed DC-DC converter (boost-type) with two input power sources based on multi-transformer structure, which is suitable for fuel cells and super-capacitors hybrid energy system, is proposed and designed. With particular transformer windings connection strategy...

Experience from design, prototyping and production of a DC-DC conversion powering scheme for the CMS Phase-1 Pixel Upgrade

International Nuclear Information System (INIS)

Feld, L.; Karpinski, W.; Klein, K.; Lipinski, M.; Preuten, M.; Rauch, M.; Schmitz, S.; Wlochal, M.

2016-01-01

The CMS collaboration has adopted a DC-DC conversion powering scheme for the Phase-1 Upgrade of its pixel detector. DC-DC buck converters with a conversion ratio of around 3 are installed on the support structures, outside of the sensitive tracking region, requiring a re-design of the low and high voltage distribution to the pixel modules. After several years of R and D, the project has entered the production phase. A total of 1800 DC-DC converters are being produced, and rigorous quality assurance and control is being employed during the production process. The testing program is outlined, results from mass production are presented and issues that have been encountered are described. In addition, two system level challenges, namely the choice of output voltage in the presence of large, load-dependent voltage drops, and the thermal management required to remove the heat load caused by the DC-DC converters, are discussed

Analytical Comparison of Dual-Input Isolated dc-dc Converter with an ac or dc Inductor for Renewable Energy Systems

DEFF Research Database (Denmark)

Zhang, Zhe; Mira Albert, Maria del Carmen; Andersen, Michael A. E.

2017-01-01

This paper presents two configurations of dualinput (DI) or three-port (TPC) isolated dc-dc converters for hybrid renewable energy systems such as photovoltaics and batteries. These two converters are derived by integrating an interleaved boost converter and a single-active bridge converter...... and control perspective, distinct in operation principles, voltage/power transfer functions, loss distributions, soft-switching constraints, and power efficiency under the same operating conditions. Moreover, the inductor design differs greatly between these two cases. In this paper, a comprehensive...

Analysis of a high power, resonant DC-DC converter for DC wind turbines

DEFF Research Database (Denmark)

Dincan, Catalin Gabriel; Kjær, Philip Carne; Chen, Yu-Hsing

2018-01-01

This paper is introducing a new method of operation for a series resonant converter, with intended application in megawatt high-voltage DC wind turbines. Compared to a frequency controlled series resonant converter operated in sub resonant mode, the method (entitled pulse removal technique) allows...

High-Efficiency Photovoltaic System Using Partially-Connected DC-DC Converter

Science.gov (United States)

Uno, Masatoshi; Kukita, Akio; Tanaka, Koji

Power conversion electronics for photovoltaic (PV) systems are desired to operate as efficiently as possible to exploit the power generated by PV modules. This paper proposes a novel PV system in which a dc-dc converter is partially connected to series-connected PV modules. The proposed system achieves high power-conversion efficiency by reducing the passing power and input/output voltages of the converter. The theoretical operating principle was experimentally validated. Resultant efficiency performances of the proposed and conventional systems demonstrated that the proposed system was more efficient in terms of power conversion though the identical converter was used for the both systems.

Very High Frequency Resonant DC/DC Converters for LED Lighting

DEFF Research Database (Denmark)

Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.

2013-01-01

This paper presents a very high frequency DC/DC converter for LED lighting. Several resonant topologies are compared and their usability discussed. At the end the resonant SEPIC converter is chosen based on the achievable power density and total bill of material. Simulations of a 51 MHz converter...... with 40 V input and 15 V output are made. The simulation shows possibility of achieving efficiency up to 87 % even with a HEXFET Power MOSFET. Three prototypes of the simulated converter are implemented showing good correlation with simulations. The prototypes have efficiencies up to 84 % and power...

Equilibrium structure and atomic vibrations of Nin clusters

Science.gov (United States)

Borisova, Svetlana D.; Rusina, Galina G.

2017-12-01

The equilibrium bond lengths and binding energy, second differences in energy and vibrational frequencies of free clusters Nin (2 ≤ n ≤ 20) were calculated with the use of the interaction potential obtained in the tight-binding approximation (TBA). The results show that the minimum vibration frequency plays a significant role in the evaluation of the dynamic stability of the clusters. A nonmonotonic dependence of the minimum vibration frequency of clusters on their size and the extreme values for the number of atoms in a cluster n = 4, 6, 13, and 19 are demonstrated. This result agrees with the theoretical and experimental data on stable structures of small metallic clusters.

A THREE-PHASE BOOST DC-AC CONVERTER

African Journals Online (AJOL)

dc-ac converter (inverter) based on the dc-dc boost converters. ... Sliding mode controllers are designed to perform a robust control for the ... Computer simulations and spectral analysis demon- ... the conventional three-phase buck inverter,.

Linking DC together with TRSL

DEFF Research Database (Denmark)

Haxthausen, Anne; Yong, Xia

1999-01-01

In this talk we present a method for linking the Duration Calculus together with the Timed RAISE Specification Language. Duration Calculus (DC) [ZHR91] is an interval-based real time logic, which can be used naturally in capturing and eliciting users' real time requirements in the form of constra......In this talk we present a method for linking the Duration Calculus together with the Timed RAISE Specification Language. Duration Calculus (DC) [ZHR91] is an interval-based real time logic, which can be used naturally in capturing and eliciting users' real time requirements in the form.......TRSL is a real-time extension of the RAISE Specification Language (RSL) [Rlg92] which together with its associated method [Rmg95]and tools has shown to be very useful in the industrial development of software systems. Therefore, a promising approach for the development of real-time systemscould be to use DC...... for high-level specifications of real-time requirementsand TRSL for specifying real-time implementations in the form of timed communicating concurrent processes.In order to link DC and TRSL together in a well-founded way, we formally define what it means for a TRSL process to satisfy a DC requirement...

A Four-Phase High Voltage Conversion Ratio Bidirectional DC-DC Converter for Battery Applications

Directory of Open Access Journals (Sweden)

Li-Kun Xue

2015-06-01

Full Text Available This study presents a four-phase interleaved high voltage conversion ratio bidirectional DC-DC converter circuit based on coupled inductors and switched capacitors, which can eliminate the defects of conventional high voltage conversion ratio bidirectional DC-DC converters in terms of high-voltage/current stress, less efficiency and low-power limitation. Parallel channels are used to reduce current stress at the low-voltage side and series connected switched capacitors are used to enlarge voltage conversion ratio, reduce voltage stress and achieve auto current sharing. This paper proposes the operation principle, feature analysis and optimization design considerations. On this basis the objectives of high voltage conversion ratio, low voltage/current stress, high power density, high efficiency and high-power applications can be achieved. Some experimental results based on a 500 W prototype converter (24 V to 48 V at low-voltage side, 400 V at high-voltage side are given to verify the theoretical analysis and the effectiveness of the proposed converter.

Model Based Optimization of Integrated Low Voltage DC-DC Converter for Energy Harvesting Applications

Science.gov (United States)

Jayaweera, H. M. P. C.; Muhtaroğlu, Ali

2016-11-01

A novel model based methodology is presented to determine optimal device parameters for the fully integrated ultra low voltage DC-DC converter for energy harvesting applications. The proposed model feasibly contributes to determine the maximum efficient number of charge pump stages to fulfill the voltage requirement of the energy harvester application. The proposed DC-DC converter based power consumption model enables the analytical derivation of the charge pump efficiency when utilized simultaneously with the known LC tank oscillator behavior under resonant conditions, and voltage step up characteristics of the cross-coupled charge pump topology. The verification of the model has been done using a circuit simulator. The optimized system through the established model achieves more than 40% maximum efficiency yielding 0.45 V output with single stage, 0.75 V output with two stages, and 0.9 V with three stages for 2.5 kΩ, 3.5 kΩ and 5 kΩ loads respectively using 0.2 V input.

Calculation of resonance integral for fuel cluster

International Nuclear Information System (INIS)

Remsak, S.

1969-01-01

The procedure for calculating the shielding correction, formulated in the previous paper [6], was broadened and applied for a cluster of cylindrical rods. The sam analytical method as in the previous paper was applied. A combination of Gauss method with the method of Almgren and Porn used for solving the same type of integral was used to calculate the geometry functions. CLUSTER code was written for ZUSE-Z-23 computer to calculate the shielding corrections for pairs of fuel rods in the cluster. Computing time for one pair of fuel rods depends on the number of closely placed rod, and for two closely placed rods it is about 3 hours. Calculations were done for clusters containing 7 and 19 UO 2 rods. results show that calculated values of resonance integrals are somewhat higher than the values obtained by Helstrand empirical formula. Taking into account the results for two rods from the previous paper it can be noted that the calculated and empirical values for clusters with 2 and 7 rods are in agreement since the deviations do not exceed the limits of experimental error (±2%). In case of larger cluster with 19 rods deviations are higher than the experimental error. Most probably the calculated values exceed the experimental ones result from the fact that in this paper the shielding correction is calculated only in the region up to 1 keV [sr

State trajectories used to observe and control dc-to-dc converters

Science.gov (United States)

Burns, W. W., III; Wilson, T. G.

1976-01-01

State-plane analysis techniques are employed to study the voltage stepup energy-storage dc-to-dc converter. Within this framework, an example converter operating under the influence of a constant on-time and a constant frequency controller is examined. Qualitative insight gained through this approach is used to develop a conceptual free-running control law for the voltage stepup converter which can achieve steady-state operation in one on/off cycle of control. Digital computer simulation data are presented to illustrate and verify the theoretical discussions presented.

Infrared spectroscopy of ionic clusters

Energy Technology Data Exchange (ETDEWEB)

Price, J.M. (California Univ., Berkeley, CA (USA). Dept. of Chemistry Lawrence Berkeley Lab., CA (USA))

1990-11-01

This thesis describes new experiments wherein the infrared vibrational predissociation spectra of a number of mass-selected ionic cluster systems have been obtained and analyzed in the 2600 to 4000 cm{sup {minus}1} region. The species studied include: the hydrated hydronium ions, H{sub 3}O{sup +} (H{sub 2}O){sub 3 {minus}10}, ammoniated ammonium ions, NH{sub 4}{sup +}(NH{sub 3}){sub 1 {minus}10} and cluster ions involving both water and ammonia around an ammonium ion core, (mixed clusters) NH{sub 4}{sup +}(NH{sub 3}){sub n}(H{sub 2}O){sub m} (n+m=4). In each case, the spectra reveal well resolved structures that can be assigned to transitions arising from the vibrational motions of both the ion core of the clusters and the surrounding neutral solvent molecules. 154 refs., 19 figs., 8 tabs.

Design of an Input-Parallel Output-Parallel LLC Resonant DC-DC Converter System for DC Microgrids

Science.gov (United States)

Juan, Y. L.; Chen, T. R.; Chang, H. M.; Wei, S. E.

2017-11-01

Compared with the centralized power system, the distributed modularized power system is composed of several power modules with lower power capacity to provide a totally enough power capacity for the load demand. Therefore, the current stress of the power components in each module can then be reduced, and the flexibility of system setup is also enhanced. However, the parallel-connected power modules in the conventional system are usually controlled to equally share the power flow which would result in lower efficiency in low loading condition. In this study, a modular power conversion system for DC micro grid is developed with 48 V dc low voltage input and 380 V dc high voltage output. However, in the developed system control strategy, the numbers of power modules enabled to share the power flow is decided according to the output power at lower load demand. Finally, three 350 W power modules are constructed and parallel-connected to setup a modular power conversion system. From the experimental results, compared with the conventional system, the efficiency of the developed power system in the light loading condition is greatly improved. The modularized design of the power system can also decrease the power loss ratio to the system capacity.

Considerations of Physical Design and Implementation for 5 MHz-100 W LLC Resonant DC-DC Converters

Directory of Open Access Journals (Sweden)

Akinori Hariya

2016-01-01

Full Text Available Recently, high power-density, high power-efficiency, and wide regulation range isolated DC-DC converters have been required. This paper presents considerations of physical design and implementation for wide regulation range MHz-level LLC resonant DC-DC converters. The circuit parameters are designed with 3–5 MHz-level switching frequency. Also, the physical parameters and the size of the planar transformer are optimized by using derived equations and finite element method (FEM with Maxwell 3D. Some experiments are done with prototype LLC resonant DC-DC converter using gallium nitride high electron mobility transistors (GaN-HEMTs; the input voltage is 42–53 V, the reference output voltage is 12 V, the load current is 8 A, the maximum switching frequency is about 5 MHz, the total volume of the circuit is 4.1 cm3, and the power density of the prototype converter is 24.4 W/cc.

Design and implementation of current fed DC-DC converter for PHEV application using renewable source

Science.gov (United States)

Milind Metha, Manish; Tutki, Sanjay; Rajan, Aju; Elangovan, D.; Arunkumar, G.

2017-11-01

As the fossil fuels are depleting day by day, the use of renewable energy sources came into existence and they evolved a lot lately. To increase efficiency and productivity in the hybrid vehicles, the existence less efficient petroleum and diesel IC engines need to be replaced with the new and efficient converters with renewable energy sources. This has to be done in such a way that impacts three factors mainly: cost, efficiency and reliability. The PHEVs that have been launched and the upcoming PHEVs using converters with voltage range around 380V to 400V generated with power ranges between 2.4KW to 2.8KW. The basic motto of this paper is to design a prolific converter while considering the factor such as cost and size. In this paper, a two stage DC-DC converter is proposed and the proposed DC-DC converter is utilized to endeavour voltage from 24V (photovoltaic source) to a yield voltage of 400V and to meet the power demand of 250W, since only one panel is being used for this proposed paper. This paper discuss in detail about why and how the current fed DC-DC converter is utilized along with a voltage doubler, thus reducing transformer turns and thereby reducing overall size of the product. Simulation and hardware results have been presented along with calculations for duty cycle required for firing sequence for different values of transformer turns.

Series-Connected High Frequency Converters in a DC Microgrid System for DC Light Rail Transit

Directory of Open Access Journals (Sweden)

Bor-Ren Lin

2018-01-01

Full Text Available This paper studies and presents a series-connected high frequency DC/DC converter connected to a DC microgrid system to provide auxiliary power for lighting, control and communication in a DC light rail vehicle. Three converters with low voltage and current stresses of power devices are series-connected with single transformers to convert a high voltage input to a low voltage output for a DC light rail vehicle. Thus, Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs with a low voltage rating and a turn-on resistance are adopted in the proposed circuit topology in order to decrease power losses on power switches and copper losses on transformer windings. A duty cycle control with an asymmetric pulse-width modulation is adopted to control the output voltage at the desired voltage level. It is also adopted to reduce switching losses on MOSFETs due to the resonant behavior from a leakage inductor of an isolated transformer and output capacitor of MOSFETs at the turn-on instant. The feasibility and effectiveness of the proposed circuit have been verified by a laboratory prototype with a 760 V input and a 24 V/60 A output.

Guest Editorial Special Issue on Structured DC Microgrids

DEFF Research Database (Denmark)

Guerrero, Josep M.; Tan, Don F. D.

2017-01-01

With the development of dc coupled devices, such as photovoltaic generations, batteries, supercapacitors, LEDs, computers, and electronics equipment, low-voltage dc distribution networks, structured dc microgrids are emerging as a natural platform to integrate renewable energy sources. However...... in either series/parallel, forming a number of dc busses with different voltage levels. Recently, with the advance of new dc power technologies, several ongoing standards, alliances, and initiatives are bringing the possibility of developing future homes, offices, buildings, campuses, datacenters, ships......, satellites, aircrafts, and other electrical power systems to operate totally or dominantly in dc. Research is being carried out in both the system and component levels of modeling, control, and stability of structured dc microgrids. New high-efficiency topologies and protections are also key nontrivial...

A new soft-switched high step-up DC-DC converter with dual coupled inductors

DEFF Research Database (Denmark)

Forouzesh, Mojtaba; Shen, Yanfeng; Yari, Keyvan

2017-01-01

This paper introduces a new efficient high step-up dc-dc converter with a shared input path and dual series coupled inductors at the output. This converter is suitable for high power applications due to its shared input current that puts low current stresses on the low voltage side switches...

75 FR 80744 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-9-81 (MD-81), DC-9-82 (MD-82...

Science.gov (United States)

2010-12-23

...-1203; Directorate Identifier 2010-NM-168-AD] RIN 2120-AA64 Airworthiness Directives; McDonnell Douglas... amends Sec. 39.13 by adding the following new airworthiness directive (AD): McDonnell Douglas Corporation... Douglas Corporation Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), DC-9-87 (MD-87) and MD-88...

Design and implementation of a bidirectional current-controlled voltage-regulated DC-DC switched-mode converter

CSIR Research Space (South Africa)

Coetzer, A

2016-01-01

Full Text Available The design and implementation of a bidirectional current-controlled voltage-regulated DC-DC converter is presented. The converter is required to connect a battery of electrochemical cells (the battery) to an asynchronous motor-drive unit via a...

A high voltage gain quasi Z-source isolated DC/DC converter

DEFF Research Database (Denmark)

Siwakoti, Yam P.; Blaabjerg, Frede; Loh, Poh Chiang

2014-01-01

A compact quasi-Z-source DC/DC converter is presented with high voltage gain, isolated output, and improved efficiency. The improvements in size and performance were achieved by using a square wave inverter with only two output switches driving an isolating transformer in push-pull mode, followed...... by a voltage doubling output rectifier. The converter is well-suited to applications requiring a high voltage gain, especially renewable energy sources such as photovoltaic and fuel-cell power supplies. To demonstrate the converter's performance a prototype designed to output 400 V at 500 W was constructed...

Four Quadrants Integrated Transformers for Dual-input Isolated DC-DC Converters

DEFF Research Database (Denmark)

Ouyang, Ziwei; Zhang, Zhe; Andersen, Michael A. E.

2012-01-01

A common limitation of power coupling effect in some known multiple-input dc-dc converters has been addressed in many literatures. In order to overcome this limitation, a new concept for decoupling the primary windings in the integrated multiple-winding transformers based on 3-dimensional (3D...... perpendicular primary windings, a name of “four quadrants integrated transformers” (FQIT) is therefore given to the proposed construction. Since the two primary windings are uncoupled, the FQIT allows the two input power stages to transfer the energy into the output load simultaneously or at any...

The cancer-immunity cycle as rational design for synthetic cancer drugs: Novel DC vaccines and CAR T-cells.

Science.gov (United States)

Ramachandran, Mohanraj; Dimberg, Anna; Essand, Magnus

2017-08-01

Cell therapy is an advanced form of cancer immunotherapy that has had remarkable clinical progress in the past decade in the search for cure of cancer. Most success has been achieved for chimeric antigen receptor (CAR) T-cells where CAR T-cells targeting CD19 show very high complete response rates for patients with refractory acute B-cell acute lymphoblastic leukemia (ALL) and are close to approval for this indication. CD19 CAR T-cells are also effective against B-cell chronic lymphoblastic leukemia (CLL) and B-cell lymphomas. Although encouraging, CAR T-cells have not yet proven clinically effective for solid tumors. This is mainly due to the lack of specific and homogenously expressed targets to direct the T-cells against and a hostile immunosuppressive tumor microenvironment in solid tumors. Cancer vaccines based on dendritic cells (DC) are also making progress although clinical efficacy is still lacking. The likelihood of success is however increasing now when individual tumors can be sequences and patient-specific neoepitopes identified. Neoepitopes and/or neoantigens can then be included in patient-based DC vaccines. This review discusses recent advancements of DC vaccines and CAR T-cells with emphasis on the cancer-immunity cycle, and current efforts to design novel cell therapies. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

High Current Planar Transformer for Very High Efficiency Isolated Boost DC-DC Converters

DEFF Research Database (Denmark)

Pittini, Riccardo; Zhang, Zhe; Andersen, Michael A. E.

2014-01-01

This paper presents a design and optimization of a high current planar transformer for very high efficiency dc-dc isolated boost converters. The analysis considers different winding arrangements, including very high copper thickness windings. The analysis is focused on the winding ac-resistance a......This paper presents a design and optimization of a high current planar transformer for very high efficiency dc-dc isolated boost converters. The analysis considers different winding arrangements, including very high copper thickness windings. The analysis is focused on the winding ac......-resistance and transformer leakage inductance. Design and optimization procedures are validated based on an experimental prototype of a 6 kW dcdc isolated full bridge boost converter developed on fully planar magnetics. The prototype is rated at 30-80 V 0-80 A on the low voltage side and 700-800 V on the high voltage side...... with a peak efficiency of 97.8% at 80 V 3.5 kW. Results highlights that thick copper windings can provide good performance at low switching frequencies due to the high transformer filling factor. PCB windings can also provide very high efficiency if stacked in parallel utilizing the transformer winding window...

Microscopic Electron Variations Measured Simultaneously By The Cluster Spacecraft

Science.gov (United States)

Buckley, A. M.; Carozzi, T. D.; Gough, M. P.; Beloff, N.

Data is used from the Particle Correlator experiments running on each of the four Cluster spacecraft so as to determine common microscopic behaviour in the elec- tron population observed over the macroscopic Cluster separations. The Cluster par- ticle correlator experiments operate by forming on board Auto Correlation Functions (ACFs) generated from short time series of electron counts obtained, as a function of electron energy, from the PEACE HEEA sensor. The information on the microscopic variation of the electron flux covers the frequency range DC up to 41 kHz (encom- passing typical electron plasma frequencies and electron gyro frequencies and their harmonics), the electron energy range is that covered by the PEACE HEEA sensor (within the range 1 eV to 26 keV). Results are presented of coherent electron struc- tures observed simultaneously by the four spacecraft in the differing plasma interac- tion regions and boundaries encountered by Cluster. As an aid to understanding the plasma interactions, use is made of numerical simulations which model both the un- derlying statistical properties of the electrons and also the manner in which particle correlator experiments operate.

DC Voltage Control and Power-Sharing of Multi-Terminal DC Grids Based on Optimal DC Power Flow and Flexible Voltage Droop Strategy

Directory of Open Access Journals (Sweden)

F. Azma

2015-06-01

Full Text Available This paper develops an effective control framework for DC voltage control and power-sharing of multi-terminal DC (MTDC grids based on an optimal power flow (OPF procedure and the voltage-droop control. In the proposed approach, an OPF algorithm is executed at the secondary level to find optimal reference of DC voltages and active powers of all voltage-regulating converters. Then, the voltage droop characteristics of voltage-regulating converters, at the primary level, are tuned based on the OPF results such that the operating point of the MTDC grid lies on the voltage droop characteristics. Consequently, the optimally-tuned voltage droop controller leads to the optimal operation of the MTDC grid. In case of variation in load or generation of the grid, a new stable operating point is achieved based on the voltage droop characteristics. By execution of a new OPF, the voltage droop characteristics are re-tuned for optimal operation of the MTDC grid after the occurrence of the load or generation variations. The results of simulation on a grid inspired by CIGRE B4 DC grid test system demonstrate efficient grid performance under the proposed control strategy.

Linking DC together with TRSL

DEFF Research Database (Denmark)

Haxthausen, Anne Elisabeth; Yong, X.

2000-01-01

in a method for real-time developments. An operational semantics with behavior is specified for TRSL. It is defined what its means for a TRSL process to satisfy a DC requirement, and a method for verifying whether the satisfaction relation holds or not is provided. Our contribution also demonstrates a general......Duration Calculus (DC) is an interval-based real-time logic, which can be used in capturing and eliciting users' real-time requirements. The Timed RAISE Specification Language (TRSL) is an extension of the RAISE Specification Language with real-time features. This paper links DC and TRSL together...

All Digital Switch-Mode DC/DC Converters with BIST Functionality for Harsh Space Environments, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The Space Micro Arizona State University (ASU) team will develop an all-digitally controlled, wide temperature range point-of-load switch-mode DC-DC regulator core...

Open-circuit fault detection and tolerant operation for a parallel-connected SAB DC-DC converter

DEFF Research Database (Denmark)

Park, Kiwoo; Chen, Zhe

2014-01-01

This paper presents an open-circuit fault detection method and its tolerant control strategy for a Parallel-Connected Single Active Bridge (PCSAB) dc-dc converter. The structural and operational characteristics of the PCSAB converter lead to several advantages especially for high power applicatio...

Meeting Materials for OECD Expert Meeting on Categorization of Manufactured Nanomaterials on September 17-19, 2014

Science.gov (United States)

Here are materials for the OECD Working Party on Nanomanufactured Materials Expert Meeting on Categorization of Nanomaterials (developing nanomaterial categories) took place on September 17-19, 2014 in Washington, D.C hosted by U.S. EPA.

Clinical efficacy of sunitinib combined with autologous DC and CIK for patients with metastatic renal cell carcinoma

Directory of Open Access Journals (Sweden)

Liang ZHANG

2014-01-01

Full Text Available Objective　To analyze the clinical efficacy and safety of sunitinib combined with autologous dentritic cell (DC and cytokine induced killer cell (CIK for patients suffering from metastatic renal cell carcinoma (mRCC. Methods　Clinical data of 27 mRCC patients treated with sunitinib combined with autologous DC and CIK were reviewed retrospectively. Efficacy, quality of life, immunology and safety of this treatment were evaluated. Results　Follow-up time ranged from 4 to 25 months. Out of all the patients, sunitinib was reduced in 1 and discontinued in 2 due to side effects; 1 patient quit for personal reasons; 14 patients developed progressive disease. The progression-free survival (PFS was 4 to 19.5 months. Ten patients died from tumor, the overall survival time (OS was 6 to 21 months. The median PFS was 16 months (95%CI 12.5-19.5. The OS was not achieved. The efficacy was evaluated according to Response Evaluation Criteria in Solid Tumors (RECIST. All the patients received treatment over 1 cycle. After one course of treatment, among 27 patients, 0 had complete remission (CR, 4 had partial remission (PR, 17 had stable disease (SD, and 6 had progressive disease (PD. The overall objective remission rate (ORR and disease control rate (DCR were 14.8% (4/27 and 77.8% (21/27, respectively. Sunitinib and autologous transfusion of DC and CIK improved the immune function and quality of life. The major adverse events were fatigue, hand-foot syndrome, hypertension, hypothyroidism, thrombocytopenia, neutropenia and fever. Most of the adverse events were ameliorated by supportive treatment or dose reduction. Conclusions　 Sunitinib combined with autologous DC and CIK may be beneficial in the treatment of mRCC with acceptable toxic reactions, and it may be considered as a new approach for the comprehensive treatment of RCC. DOI: 10.11855/j.issn.0577-7402.2013.12.06

Hierarchical Power Sharing Control in DC Microgrids

DEFF Research Database (Denmark)

Peyghami, Saeed; Mokhtari, Hossein; Blaabjerg, Frede

2016-01-01

Because of the advances in power electronics, DC-based power systems, have been used in industrial applications such as data centers [18], space applications [10], aircraft [12], offshore wind farms, electric vehicles [56], DC home systems [5, 20], and high-voltage DC transmission systems...

Structures, stabilities, and electronic properties for rare-earth lanthanum doped gold clusters

International Nuclear Information System (INIS)

Zhao, Ya-Ru

2015-01-01

The structures, stabilities, and electronic properties of rare-earth lanthanum doped gold La 2 Au n (n = 1-9) and pure gold Au n (n ≤ 11) clusters have been investigated by using density functional theory. The optimized geometries show that the lowest energy structures of La 2 Au n clusters favour the 3D structure at n ≥ 3. The lanthanum atoms can strongly enhance the stabilities of gold clusters and tend to occupy the most highly coordinated position. By analysing the gap, vertical ionization potential, and chemical hardness, it is found that the La 2 Au 6 isomer possesses higher stability for small-sized La 2 Au n clusters (n = 1-9). The charges in the La 2 Au n clusters transfer from La atoms to the Au n host. In addition, Wiberg bond indices analysis reveals that the intensity of different bonds of La 2 Au n clusters exhibits a sequence of La-La bond > La-Au bond > Au-Au bond.

75 FR 38017 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-9-10 Series Airplanes, DC-9-30...

Science.gov (United States)

2010-07-01

... Airworthiness Directives; McDonnell Douglas Corporation Model DC- 9-10 Series Airplanes, DC-9-30 Series... previously to all known U.S. owners and operators of the McDonnell Douglas Corporation airplanes identified... INFORMATION: On July 15, 2009, we issued AD 2009-15-16, which applies to all McDonnell Douglas Model DC-9-10...

THE M33 GLOBULAR CLUSTER SYSTEM WITH PAndAS DATA: THE LAST OUTER HALO CLUSTER?

International Nuclear Information System (INIS)

Cockcroft, Robert; Harris, William E.; Ferguson, Annette M. N.

2011-01-01

We use CFHT/MegaCam data to search for outer halo star clusters in M33 as part of the Pan-Andromeda Archaeological Survey. This work extends previous studies out to a projected radius of 50 kpc and covers over 40 deg 2 . We find only one new unambiguous star cluster in addition to the five previously known in the M33 outer halo (10 kpc ≤ r ≤ 50 kpc). Although we identify 2440 cluster candidates of various degrees of confidence from our objective image search procedure, almost all of these are likely background contaminants, mostly faint unresolved galaxies. We measure the luminosity, color, and structural parameters of the new cluster in addition to the five previously known outer halo clusters. At a projected radius of 22 kpc, the new cluster is slightly smaller, fainter, and redder than all but one of the other outer halo clusters, and has g' ∼ 19.9, (g' - i') ∼ 0.6, concentration parameter c ∼ 1.0, a core radius r c ∼ 3.5 pc, and a half-light radius r h ∼ 5.5 pc. For M33 to have so few outer halo clusters compared to M31 suggests either tidal stripping of M33's outer halo clusters by M31, or a very different, much calmer accretion history of M33.

Experimental study of dynamic behaviors and routes to chaos in DC-DC boost converters

International Nuclear Information System (INIS)

Cafagna, D.; Grassi, G.

2005-01-01

This paper illustrates an experimental study of a current-programmed DC-DC boost converter, with the aim of investigating possible pathways through which the converter may enter chaos. In particular, based on experimental measurements, it is shown that variations of input voltage and reference current can generate periodic, subharmonic, quasi-periodic and chaotic behaviors

Halbach array DC motor/generator

Science.gov (United States)

Merritt, B.T.; Dreifuerst, G.R.; Post, R.F.

1998-01-06

A new configuration of DC motor/generator is based on a Halbach array of permanent magnets. This motor does not use ferrous materials so that the only losses are winding losses and losses due to bearings and windage. An ``inside-out`` design is used as compared to a conventional motor/generator design. The rotating portion, i.e., the rotor, is on the outside of the machine. The stationary portion, i.e., the stator, is formed by the inside of the machine. The rotor contains an array of permanent magnets that provide a uniform field. The windings of the motor are placed in or on the stator. The stator windings are then ``switched`` or ``commutated`` to provide a DC motor/generator much the same as in a conventional DC motor. The commutation can be performed by mechanical means using brushes or by electronic means using switching circuits. The invention is useful in electric vehicles and adjustable speed DC drives. 17 figs.

Halbach array DC motor/generator

Science.gov (United States)

Merritt, Bernard T.; Dreifuerst, Gary R.; Post, Richard F.

1998-01-01

A new configuration of DC motor/generator is based on a Halbach array of permanent magnets. This motor does not use ferrous materials so that the only losses are winding losses and losses due to bearings and windage. An "inside-out" design is used as compared to a conventional motor/generator design. The rotating portion, i.e., the rotor, is on the outside of the machine. The stationary portion, i.e., the stator, is formed by the inside of the machine. The rotor contains an array of permanent magnets that provide a uniform field. The windings of the motor are placed in or on the stator. The stator windings are then "switched" or "commutated" to provide a DC motor/generator much the same as in a conventional DC motor. The commutation can be performed by mechanical means using brushes or by electronic means using switching circuits. The invention is useful in electric vehicles and adjustable speed DC drives.

Bifurcation Analysis of a DC-DC Bidirectional Power Converter Operating with Constant Power Loads

Science.gov (United States)

Cristiano, Rony; Pagano, Daniel J.; Benadero, Luis; Ponce, Enrique

Direct current (DC) microgrids (MGs) are an emergent option to satisfy new demands for power quality and integration of renewable resources in electrical distribution systems. This work addresses the large-signal stability analysis of a DC-DC bidirectional converter (DBC) connected to a storage device in an islanding MG. This converter is responsible for controlling the balance of power (load demand and generation) under constant power loads (CPLs). In order to control the DC bus voltage through a DBC, we propose a robust sliding mode control (SMC) based on a washout filter. Dynamical systems techniques are exploited to assess the quality of this switching control strategy. In this sense, a bifurcation analysis is performed to study the nonlinear stability of a reduced model of this system. The appearance of different bifurcations when load parameters and control gains are changed is studied in detail. In the specific case of Teixeira Singularity (TS) bifurcation, some experimental results are provided, confirming the mathematical predictions. Both a deeper insight in the dynamic behavior of the controlled system and valuable design criteria are obtained.

Feasibility analysis of the application and positioning of DC HTS FCL in a DC microgrid through modeling and simulation using Simulink and SimPowerSystem

Energy Technology Data Exchange (ETDEWEB)

Khan, U.A.; Shin, W.J.; Seong, J.K.; Oh, S.H.; Lee, S.H. [School of Electrical Engineering and Computer Science, Hanyang University, Ansan-Shi, Gyeonggi-do 426-791 (Korea, Republic of); Lee, B.W., E-mail: bangwook@hanyang.ac.kr [School of Electrical Engineering and Computer Science, Hanyang University, Ansan-Shi, Gyeonggi-do 426-791 (Korea, Republic of)

2011-11-15

We modeled DC SFCL by use of SimPowerSystem blocks. We examine the DC fault current limitation in low voltage DC distribution networks. SFCL's affects at critical points were measured. SFCL installed at the substation rectifier branch resulted in abnormal increase of fault current. The strategic location of SFCL is the point of integration of the PV plant with the power grid. DC fault current limitation in DC distribution network is one of the critical issues which need to be taken care of before they can be practically implemented. High temperature superconductors could be efficiently installed to cope with the problem of DC fault currents. In this paper, a generalized DC high temperature superconducting fault current limiter (SFCL) is modeled by integrating Simulink and SimPowerSystem blocks. This model is designed for limiting DC fault currents in low voltage DC distribution networks. A DC microgrid having a low voltage DC distribution network, an integrated photovoltaic plant and domestic customer load is modeled. Transient analysis of the DC microgrid is performed by generating fault and measuring DC fault currents at critical points. The designed DC SFCL is placed at different strategic locations in DC microgrid and fault current limitation performance of DC SFCL in DC microgrid has been analyzed. Moreover, the affects of rapid impedance changing in the distribution network due to the fault followed by DC SFCL activation is investigated. Finally, the best suitable position and affects of DC SFCL in a DC microgrid along with suggestions for implementation have been proposed.

Feasibility analysis of the application and positioning of DC HTS FCL in a DC microgrid through modeling and simulation using Simulink and SimPowerSystem

International Nuclear Information System (INIS)

Khan, U.A.; Shin, W.J.; Seong, J.K.; Oh, S.H.; Lee, S.H.; Lee, B.W.

2011-01-01

We modeled DC SFCL by use of SimPowerSystem blocks. We examine the DC fault current limitation in low voltage DC distribution networks. SFCL's affects at critical points were measured. SFCL installed at the substation rectifier branch resulted in abnormal increase of fault current. The strategic location of SFCL is the point of integration of the PV plant with the power grid. DC fault current limitation in DC distribution network is one of the critical issues which need to be taken care of before they can be practically implemented. High temperature superconductors could be efficiently installed to cope with the problem of DC fault currents. In this paper, a generalized DC high temperature superconducting fault current limiter (SFCL) is modeled by integrating Simulink and SimPowerSystem blocks. This model is designed for limiting DC fault currents in low voltage DC distribution networks. A DC microgrid having a low voltage DC distribution network, an integrated photovoltaic plant and domestic customer load is modeled. Transient analysis of the DC microgrid is performed by generating fault and measuring DC fault currents at critical points. The designed DC SFCL is placed at different strategic locations in DC microgrid and fault current limitation performance of DC SFCL in DC microgrid has been analyzed. Moreover, the affects of rapid impedance changing in the distribution network due to the fault followed by DC SFCL activation is investigated. Finally, the best suitable position and affects of DC SFCL in a DC microgrid along with suggestions for implementation have been proposed.

A DC-DC Converter with Wide Input Voltage Range for Fuel Cell and Supercapacitor Application

DEFF Research Database (Denmark)

Zhang, Zhe; Thomsen, Ole Cornelius; Andersen, Michael Andreas E.

2009-01-01

This paper proposes a novel phase-shift plus duty cycle controlled hybrid bi-directional DC-DC converter based on fuel cells and supercapacitors. The described converter employs two high frequency transformers to couple the half-bridge and full-bridge circuits together in the primary side...

Step-Up Partial Power DC-DC Converters for Two-Stage PV Systems with Interleaved Current Performance

Directory of Open Access Journals (Sweden)

Jaime Wladimir Zapata

2018-02-01

Full Text Available This work presents a partial power converter allowing us to obtain, with a single DC-DC converter, the same feature as the classical interleaved operation of two converters. More precisely, the proposed topology performs similarly as the input-parallel output-series (IPOS configuration reducing the current ripple at the input of the system and dividing the individual converters power rating, compared to a single converter. The proposed topology consists of a partial DC-DC converter processing only a fraction of the total power, thus allowing high efficiency. Experimental results are provided to validate the proposed converter topology with a Flyback-based 100 W test bench with a transformer turns ratio n 1 = n 2 . Experimental results show high performances reducing the input current ripple around 30 % , further increasing the conversion efficiency.

Targeting of macrophage galactose-type C-type lectin (MGL) induces DC signaling and activation

DEFF Research Database (Denmark)

Napoletano, Chiara; Zizzari, Ilaria G; Rughetti, Aurelia

2012-01-01

NAc or Tn)-carrying tumor-associated antigens to improve DC performance. MGL expressed by ex vivo-generated iDCs from healthy donors was engaged by a 60-mer MUC1(9Tn) -glycopeptide as a Tn-carrying tumor-associated antigen, and an anti-MGL antibody, as a specific MGL binder. We demonstrated that MGL......Dendritic cells (DCs) sense the microenvironment through several types of receptors recognizing pathogen-associated molecular patterns. In particular, C-type lectins, expressed by distinct subsets of DCs, recognize and internalize specific carbohydrate antigen in a Ca(2+) -dependent manner....... Targeting of these receptors is becoming an efficient strategy of delivering antigens in DC-based anticancer immunotherapy. Here we investigated the role of the macrophage galactose type C-lectin receptor (MGL), expressed by immature DCs (iDCs), as a molecular target for a-N-acetylgalactosamine (Gal...

Performance analysis of pulse analog control schemes for LLC resonant DC/DC converters suitable in portable applications

Directory of Open Access Journals (Sweden)

P. Kowstubha

2016-12-01

Full Text Available Performance Analysis of Pulse Analog Control Schemes, predominantly Pulse-Width Modulation (PWM and Pulse-Position Modulation (PPM for LLC resonant DC/DC converter suitable in portable applications is addressed in this paper. The analysis is done for closed loop performance, frequency domain performance, primary and secondary side conduction losses and soft commutation using PSIM 6.0 software and observed that PPM scheme provides better performance at high input voltage with a good selectivity of frequency over a wide range of line and load variations. The performance of LLC resonant DC/DC converter is demonstrated using PPM scheme for a design specifications of 12 V, 5 A output.

State-plane analysis of zero-voltage-switching resonant dc/dc power converters

Science.gov (United States)

Kazimierczuk, Marian K.; Morse, William D.

The state-plane analysis technique for the zero-voltage-switching resonant dc/dc power converter family of topologies, namely the buck, boost, buck-boost, and Cuk converters is established. The state plane provides a compression of information that allows the designer to uniquely examine the nonlinear dynamics of resonant converter operation. Utilizing the state plane, resonant converter modes of operation are examined and the switching frequencies are derived for the boundaries between these modes, including the boundary of energy conversion.

Cost-based droop scheme for DC microgrid

DEFF Research Database (Denmark)

Nutkani, Inam Ullah; Wang, Peng; Loh, Poh Chiang

2014-01-01

voltage level, less on optimized operation and control of generation sources. The latter theme is perused in this paper, where cost-based droop scheme is proposed for distributed generators (DGs) in DC microgrids. Unlike traditional proportional power sharing based droop scheme, the proposed scheme......-connected operation. Most importantly, the proposed scheme can reduce overall total generation cost in DC microgrids without centralized controller and communication links. The performance of the proposed scheme has been verified under different load conditions.......DC microgrids are gaining interest due to higher efficiencies of DC distribution compared with AC. The benefits of DC systems have been widely researched for data centers, IT facilities and residential applications. The research focus, however, has been more on system architecture and optimal...

Novel Step-Up DC/DC Converter with No Right Half Plane Zero and Reduced Switched Voltage Stress Characteristics

DEFF Research Database (Denmark)

Mostaan, Ali; Alizadeh, Ebrahim; Soltani, Mohsen

2014-01-01

and the voltage transfer gain is obtained. It is also demonstrated that the voltage stress on all semiconductor devices is restricted to input voltage which allows the utilization of a power switch with lower drain source resistance. In order to further increase the voltage gain another switched capacitor voltage......Novel step-up DC/DC converter is introduced in this paper. This converter is realized with adding the switched capacitor voltage multiplier cell to the three switch step-down DC/DC converter that has been proposed in the literature. The proposed converter is analyzed in the steady state...

Multichannel DC SQUID sensor array for biomagnetic applications

International Nuclear Information System (INIS)

Hoenig, H.E.; Daalmans, G.M.; Bar, L.; Bommel, F.; Paulus, A.; Uhl, D.; Weisse, H.J.; Schneider, S.; Seifert, H.; Reichenberger, H.; Abraham-Fuchs, K.

1991-01-01

This paper reports on a biomagnetic multichannel system for medical diagnosis of brain and heart KRENIKON has been developed. 37 axial 2st order gradiometers - manufactured as flexible superconducting printed circuits - are arranged in a circular flat array of 19 cm diameter. Additionally, 3 orthogonal magnetometers are provided. The DC SQUIDs are fabricated in all-Nb technology, ten on a chip. The sensor system is operated in a shielded room with two layers of soft magnetic material and one layer of Al. The every day noise level is 10 fT/Hz 1/2 at frequencies above 10 Hz. Within 2 years of operation in a normal urban surrounding, useful clinical applications have been demonstrated (e.g. for epilepsy and heart arrhythmias)

Circuit description of unipolar DC-to-DC converters for APS storage ring quadrupoles and sextupoles

International Nuclear Information System (INIS)

McGhee, D.G.

1993-01-01

This paper describes the control, interlock, and power circuits for 680 unipolar switch mode DC-to-DC converters used to regulate the Advanced Photon Sources (APS's) storage ring quadrupole and sextupole magnet currents. Quadrupole current stability is ± 6x10 -5 and the sextupole current stability is ±3x10 -4 . The stability is obtained with pulse width modulation, operating at a switching frequency of 20kHz with full current switching. The converters are housed in 200 cabinets located on top of the storage ring tunnel. Raw DC power is distributed from 80 AC-to-DC power supplies, four at each of 20 locations around the storage ring. Voltages, currents, and temperatures are computer monitored and logged for the converters and magnets. All converters and magnets are water cooled with the flow and pressure monitored at the inlet and outlet of groups. Water is interlocked with the raw power supplies and not the individual converters

Chaos control in solar fed DC-DC boost converter by optimal parameters using nelder-mead algorithm powered enhanced BFOA

Science.gov (United States)

Sudhakar, N.; Rajasekar, N.; Akhil, Saya; Jyotheeswara Reddy, K.

2017-11-01

The boost converter is the most desirable DC-DC power converter for renewable energy applications for its favorable continuous input current characteristics. In other hand, these DC-DC converters known as practical nonlinear systems are prone to several types of nonlinear phenomena including bifurcation, quasiperiodicity, intermittency and chaos. These undesirable effects has to be controlled for maintaining normal periodic operation of the converter and to ensure the stability. This paper presents an effective solution to control the chaos in solar fed DC-DC boost converter since the converter experiences wide range of input power variation which leads to chaotic phenomena. Controlling of chaos is significantly achieved using optimal circuit parameters obtained through Nelder-Mead Enhanced Bacterial Foraging Optimization Algorithm. The optimization renders the suitable parameters in minimum computational time. The results are compared with the traditional methods. The obtained results of the proposed system ensures the operation of the converter within the controllable region.

Small-Signal Analysis of Single-Phase and Three-phase DC/AC and AC/DC PWM Converters with the Frequency-Shift Technique

DEFF Research Database (Denmark)

Blaabjerg, Frede; Aquila, A. Dell’; Liserre, Marco

2004-01-01

of dc/dc converters via a 50 Hz frequency-shift. The input admittance is calculated and measured for two study examples (a three-phase active rectifier and a single-phase photovoltaic inverter). These examples show that the purpose of a well designed controller for grid-connected converters......A systematic approach to study dc/ac and ac/dc converters without the use of synchronous transformation is proposed. The use of a frequency-shift technique allows a straightforward analysis of single-phase and three-phase systems. The study of dc/ac and of ac/dc converters is reported to the study...... is to minimize the input admittance in order to make the grid converter more robust to grid disturbance....

Design and Control of a Multiple Input DC/DC Converter for Battery/Ultra-capacitor Based Electric Vehicle Power System

DEFF Research Database (Denmark)

Schaltz, Erik; Li, Zhihao; Onar, Omer

2009-01-01

Battery/Ultra-capacitor based electrical vehicles (EV) combine two energy sources with different voltage levels and current characteristics. This paper focuses on design and control of a multiple input DC/DC converter, to regulate output voltage from different inputs. The proposed multi-input con......Battery/Ultra-capacitor based electrical vehicles (EV) combine two energy sources with different voltage levels and current characteristics. This paper focuses on design and control of a multiple input DC/DC converter, to regulate output voltage from different inputs. The proposed multi...

Design and Implementation of Battery Charger with Power Factor Correction Using Sepic Converter and Full-bridge DC-DC Converter

OpenAIRE

Efendi, Moh. Zaenal; Windarko, Novie Ayub; Amir, Moh. Faisal

2013-01-01

This paper presents a design and implementation of a converter which has a high power factor for battery charger application. The converter is a combination of a SEPIC converter and a full-bridge DC-DC converter connected in two stages of series circuit. The SEPIC converter works in discontinuous conduction mode and it serves as a power factor corrector so that the shape of input current waveform follows the shape of input voltage waveform. The full-bridge DC-DC converter serves as a regulato...

Periodically Swapping Modulation (PSM) Strategy for Three-Level (TL) DC/DC Converter with Balanced Switch Currents

DEFF Research Database (Denmark)

Liu, Dong; Deng, Fujin; Zhang, Qi

2018-01-01

The asymmetrical modulation strategy is widely used in various types of three-level (TL) DC/DC converters, while the current imbalance among the power switches is one of the important issues. In this paper, a novel periodically swapping modulation (PSM) strategy is proposed for balancing the power...... switches’ currents in various types of TL DC/DC converters. In the proposed PSM strategy, the driving signals of the switch pairs are swapped periodically, which guarantees that the currents through the power switches are kept balanced in every two switching periods. Therefore, the proposed PSM...... strategy can effectively improve the reliability of the converter by balancing the power losses and thermal stresses among the power switches. The operation principle and performances of the proposed PSM strategy are analyzed in detail. Finally, the simulation and experimental results are presented...

Galaxy Clusters in the Swift/BAT era II: 10 more Clusters detected above 15 keV

Energy Technology Data Exchange (ETDEWEB)

Ajello, M.; /SLAC /KIPAC, Menlo Park; Rebusco, P.; /KIPAC, Menlo Park; Cappelluti, N.; /Garching, Max Planck Inst., MPE /Maryland U., Baltimore County; Reimer, O.; /SLAC /Palermo Observ.; Boehringer, H.; /Garching, Max Planck Inst., MPE; La Parola, V.; Cusumano, G.; /Palermo Observ.

2010-10-27

We report on the discovery of 10 additional galaxy clusters detected in the ongoing Swift/BAT all-sky survey. Among the newly BAT-discovered clusters there are: Bullet, Abell 85, Norma, and PKS 0745-19. Norma is the only cluster, among those presented here, which is resolved by BAT. For all the clusters we perform a detailed spectral analysis using XMM-Newton and Swift/BAT data to investigate the presence of a hard (non-thermal) X-ray excess. We find that in most cases the clusters emission in the 0.3-200 keV band can be explained by a multi-temperature thermal model confirming our previous results. For two clusters (Bullet and Abell 3667) we find evidence for the presence of a hard X-ray excess. In the case of the Bullet cluster, our analysis confirms the presence of a non-thermal, power-law like, component with a 20-100 keV flux of 3.4 x 10{sup -12} erg cm{sup -2} s{sup -1} as detected in previous studies. For Abell 3667 the excess emission can be successfully modeled as a hot component (kT = {approx}13 keV). We thus conclude that the hard X-ray emission from galaxy clusters (except the Bullet) has most likely thermal origin.

GALAXY CLUSTERS IN THE SWIFT/BAT ERA. II. 10 MORE CLUSTERS DETECTED ABOVE 15 keV

International Nuclear Information System (INIS)

Ajello, M.; Reimer, O.; Rebusco, P.; Cappelluti, N.; Boehringer, H.; La Parola, V.; Cusumano, G.

2010-01-01

We report on the discovery of 10 additional galaxy clusters detected in the ongoing Swift/Burst Alert Telescope (BAT) all-sky survey. Among the newly BAT-discovered clusters there are Bullet, A85, Norma, and PKS 0745-19. Norma is the only cluster, among those presented here, which is resolved by BAT. For all the clusters, we perform a detailed spectral analysis using XMM-Newton and Swift/BAT data to investigate the presence of a hard (non-thermal) X-ray excess. We find that in most cases the clusters' emission in the 0.3-200 keV band can be explained by a multi-temperature thermal model confirming our previous results. For two clusters (Bullet and A3667), we find evidence for the presence of a hard X-ray excess. In the case of the Bullet cluster, our analysis confirms the presence of a non-thermal, power-law-like, component with a 20-100 keV flux of 3.4 x 10 -12 erg cm -2 s -1 as detected in previous studies. For A3667, the excess emission can be successfully modeled as a hot component (kT ∼ 13 keV). We thus conclude that the hard X-ray emission from galaxy clusters (except the Bullet) has most likely a thermal origin.

Distributed maximum power point tracking in photovoltaic applications: active bypass DC/DC converter

Directory of Open Access Journals (Sweden)

Carlos Andrés Ramos-Paja

2012-01-01

Full Text Available Se propone una estructura de desvío activo para maximizar la producción de potencia en sistemas fotovoltaicos bajo condiciones irregulares de operación, comparando su eficiencia con soluciones individuales y distribuidas basadas en convertidores DC/DC convencionales. Los análisis y simulaciones realistas demuestran las ventajas del nuevo convertidor de desvío activo sobre soluciones basadas en convertidores Boost, Buck y Buck-Boost.

Modelling, Simulation and Construction of a DC/DC Boost Power Converter: A School Experimental System

Science.gov (United States)

Silva-Ortigoza, R.; Silva-Ortigoza, G.; Hernandez-Guzman, V. M.; Saldana-Gonzalez, G.; Marcelino-Aranda, M.; Marciano-Melchor, M.

2012-01-01

We introduce a dc/dc boost power converter as a didactic prototype intended to support courses on electric circuit analysis experimentally. The corresponding mathematical model is obtained, the converter is designed and an experimental setup is described, constructed and tested. Simplicity of construction as well as low cost of components renders…

A review on DC/DC converter architectures for power fuel cell applications

International Nuclear Information System (INIS)

Kolli, Abdelfatah; Gaillard, Arnaud; De Bernardinis, Alexandre; Bethoux, Olivier; Hissel, Daniel; Khatir, Zoubir

2015-01-01

Highlights: • Different DC/DC power converter topologies for Fuel Cell systems are presented. • Advantages and drawbacks of the DC/DC power converter topologies are detailed. • Wide-BandGap semiconductors are attractive candidates for design of converters. • Wide-BandGap semiconductors improve efficiency and thermal limits of converters. • Different semiconductor technologies are assessed. - Abstract: Fuel cell-based power sources are attractive devices. Through multi-stack architecture, they offer flexibility, reliability, and efficiency. Keys to accessing the market are simplifying its architecture and each components. These include, among others, the power converter enabling the output voltage regulation. This article focuses on this specific component. The present paper gives a comprehensive overview of the power converter interfaces potentially favorable for the automotive, railways, aircrafts and small stationary domains. First, with respect to the strategic development of a modular design, it defines the specifications of a basic interface. Second, it inventories the best architecture opportunities with respect to these requirements. Based on this study, it fully designs a basic module and points out the outstanding contribution of the new developed silicon carbide switch technology. In conclusion, this review article exhibits the importance of choosing the right power converter architecture and the related technology. In this context it is highlighted that the output power interface can be efficient, compact and modular. In addition, its features enable a thermal compatibility with many ways of integrating this component in the global fuel cell based power source.

A single-phase embedded Z-source DC-AC inverter.

Science.gov (United States)

Kim, Se-Jin; Lim, Young-Cheol

2014-01-01

In the conventional DC-AC inverter consisting of two DC-DC converters with unipolar output capacitors, the output capacitor voltages of the DC-DC converters must be higher than the DC input voltage. To overcome this weakness, this paper proposes a single-phase DC-AC inverter consisting of two embedded Z-source converters with bipolar output capacitors. The proposed inverter is composed of two embedded Z-source converters with a common DC source and output AC load. Though the output capacitor voltages of the converters are relatively low compared to those of a conventional inverter, an equivalent level of AC output voltages can be obtained. Moreover, by controlling the output capacitor voltages asymmetrically, the AC output voltage of the proposed inverter can be higher than the DC input voltage. To verify the validity of the proposed inverter, experiments were performed with a DC source voltage of 38 V. By controlling the output capacitor voltages of the converters symmetrically or asymmetrically, the proposed inverter can produce sinusoidal AC output voltages. The experiments show that efficiencies of up to 95% and 97% can be achieved with the proposed inverter using symmetric and asymmetric control, respectively.

Power Quality in DC Power Distribution Systems and Microgrids

Directory of Open Access Journals (Sweden)

Stephen Whaite

2015-05-01

Full Text Available This review paper discusses power quality considerations for direct current (DC electric power distribution systems, particularly DC microgrids. First, four selected sample DC architectures are discussed to provide motivation for the consideration of power quality in DC systems. Second, a brief overview of power quality challenges in conventional alternating current (AC distribution systems is given to establish the field of power quality. Finally, a survey of literature addressing power quality issues in DC systems is presented, and necessary power quality considerations in DC distribution system design and operation are discussed.

Family of Step-up DC/DC Converters with Fast Dynamic Response for Low Power Applications

DEFF Research Database (Denmark)

N. Soltani, Mohsen; Mostaan, Ali; Siwakoti, Yam Prasad

2016-01-01

This study presents a family of novel step-up DC/DC converters which do not have a right half plane zero in their transfer function resulting in faster dynamic behaviour of the converters under the load variation. In addition, the voltage stress on all the active switches and diodes is as low...

Ultra-Step-Up DC-DC Converter with Integrated Autotransformer and Coupled Inductor

DEFF Research Database (Denmark)

Siwakoti, Yam Prasad; Blaabjerg, Frede; Loh, Poh Chiang

2016-01-01

This paper introduces a new single-switch nonisolated dc-dc converter with very high voltage transfer ratio and reduced semiconductor voltage stress. The converter utilizes an integrated autotransformer and a coupled inductor on the same core to achieve a high step-up voltage gain without extreme...... duty cycle. Further, an integrated passive regenerative circuit recycles the leakage energy of the coupled magnetics and transfer the leakage energy to the load, which helps to avoid high voltage spikes across the switch. This feature along with low stress on the switching device enables the designer...

Simultaneous distribution of AC and DC power

Science.gov (United States)

Polese, Luigi Gentile

2015-09-15

A system and method for the transport and distribution of both AC (alternating current) power and DC (direct current) power over wiring infrastructure normally used for distributing AC power only, for example, residential and/or commercial buildings' electrical wires is disclosed and taught. The system and method permits the combining of AC and DC power sources and the simultaneous distribution of the resulting power over the same wiring. At the utilization site a complementary device permits the separation of the DC power from the AC power and their reconstruction, for use in conventional AC-only and DC-only devices.

A New Control Method for a Bi-Directional Phase-Shift-Controlled DC-DC Converter with an Extended Load Range

Directory of Open Access Journals (Sweden)

Wenzheng Xu

2017-10-01

Full Text Available Phase-shifted converters are practically important to provide high conversion efficiencies through soft-switching techniques. However, the limitation on a resonant inductor current in the converters often leads to a non-fulfillment of the requirement of minimum load current. This paper presents a new power electronics control technique to enable the dual features of bi-directional power flow and an extended load range for soft-switching in phase-shift-controlled DC-DC converters. The proposed technique utilizes two identical full bridge converters and inverters in conjunction with a new control logic for gate-driving signals to facilitate both Zero Current Switching (ZCS and Zero Voltage Switching (ZVS in a single phase-shift-controlled DC-DC converter. The additional ZCS is designed for light load conditions at which the minimum load current cannot be attained. The bi-directional phase-shift-controlled DC-DC converter can implement the function of synchronous rectification. Its fast dynamic response allows for quick energy recovery during the regenerative braking of traction systems in electrified trains.

Multi-cell DC-DC converters : modelling, analysis and control

International Nuclear Information System (INIS)

Feki, M.; El Aroudi, A.; Robert, B.G.M.

2011-01-01

This paper is devoted to modeling of a two-cell DC/DC buck converter, to the analysis of its behavior and to the design of control methods that yield to improve its performances. Various numerical simulations and dynamical aspects of this system are illustrated in the time domain and in the parameter space. Without control, the system may present many undesirable behaviors such as sub-harmonics and chaotic oscillations. The proposed controllers are able to widen the stability range of the system. Optimum values of parameters giving rise to fast response while maintaining stable periodic behavior are given in closed form. However, it is detected that in a certain region of the parameter space, the stabilized periodic orbit may coexist with a chaotic attractor. Boundary between basins of attraction are obtained by means of numerical simulations.

Electron attenuation in free, neutral ethane clusters.

Science.gov (United States)

Winkler, M; Myrseth, V; Harnes, J; Børve, K J

2014-10-28

The electron effective attenuation length (EAL) in free, neutral ethane clusters has been determined at 40 eV kinetic energy by combining carbon 1s x-ray photoelectron spectroscopy and theoretical lineshape modeling. More specifically, theory is employed to form model spectra on a grid in cluster size (N) and EAL (λ), allowing N and λ to be determined by optimizing the goodness-of-fit χ(2)(N, λ) between model and observed spectra. Experimentally, the clusters were produced in an adiabatic-expansion setup using helium as the driving gas, spanning a range of 100-600 molecules in mean cluster size. The effective attenuation length was determined to be 8.4 ± 1.9 Å, in good agreement with an independent estimate of 10 Å formed on the basis of molecular electron-scattering data and Monte Carlo simulations. The aggregation state of the clusters as well as the cluster temperature and its importance to the derived EAL value are discussed in some depth.

Input-Parallel Output-Parallel Three-Level DC/DC Converters With Interleaving Control Strategy for Minimizing and Balancing Capacitor Ripple Currents

DEFF Research Database (Denmark)

Liu, Dong; Deng, Fujin; Gong, Zheng

2017-01-01

In this paper, the input-parallel output-parallel (IPOP) three-level (TL) DC/DC converters associated with the interleaving control strategy are proposed for minimizing and balancing the capacitor ripple currents. The proposed converters consist of two four-switch half-bridge three-level (HBTL) DC...

Thermal motion of carbon clusters and production of carbon nanotubes by gravity-free arc discharge

International Nuclear Information System (INIS)

Mieno, T.; Takeguchi, M.

2006-01-01

Thermal and diffusion properties of hot gas around a dc arc discharge under a gravity-free condition are investigated using a jet plane in order to improve the arc production of carbon clusters. Spherically symmetric temperature distribution of He gas around the arc plasma and monotonic slow expansion of the high-temperature region are observed. By means of the passive-type Mie scattering method, random slow diffusion of carbon clusters around the arc plasma is clearly observed under the gravity-free condition. This indicates that carbon clusters including single-walled carbon nanotubes are synthesized around the arc plasma where the He temperature is higher than 1000 K. It is confirmed that large bundles of fatter single-walled carbon nanotubes are produced under the gravity-free condition

BaltDC: purification, characterization and infrared spectroscopy of an antiplatelet DC protein isolated from Bothrops alternatus snake venom.

Science.gov (United States)

Matias, Mariana Santos; de Sousa, Bruna Barbosa; da Cunha Pereira, Déborah Fernanda; Dias, Edigar Henrique Vaz; Mamede, Carla Cristine Neves; de Queiroz, Mayara Ribeiro; Silva, Anielle Christine Almeida; Dantas, Noelio Oliveira; Soares, Andreimar Martins; de Oliveira Costa, Júnia; de Oliveira, Fábio

2017-01-01

Snake venoms are a complex mixture of proteins, organic and inorganic compounds. Some of these proteins, enzymatic or non-enzymatic ones, are able to interact with platelet receptors, causing hemostatic disorders. The possible therapeutic potential of toxins with antiplatelet properties may arouse interest in the pharmacological areas. The present study aimed to purify and characterize an antiplatelet DC protein from Bothrops alternatus snake venom. The protein, called BaltDC (DC protein from B. alternatus snake venom), was purified by a combination of ion-exchange chromatography on DEAE-Sephacel column and gel filtration on Sephadex G-75. The molecular mass was estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE). The amino acid sequence of the N-terminal region was carried out by Edman degradation method. Platelet aggregation assays were performed in human platelet-rich plasma (PRP). Infrared (IR) spectroscopy was used in order to elucidate the interactions between BaltDC and platelet membrane. BaltDC ran as a single protein band on SDS-PAGE and showed apparent molecular mass of 32 kDa under reducing or non-reducing conditions. The N-terminal region of the purified protein revealed the amino acid sequence IISPPVCGNELLEVGEECDCGTPENCQNECCDA, which showed identity with other snake venom metalloproteinases (SVMPs). BaltDC was devoid of proteolytic, hemorrhagic, defibrinating or coagulant activities, but it showed a specific inhibitory effect on platelet aggregation induced by ristocetin and epinephrine in PRP. IR analysis spectra strongly suggests that PO 3 2- groups, present in BaltDC, form hydrogen bonds with the PO 2 - groups present in the non-lipid portion of the membrane platelets. BaltDC may be of medical interest since it was able to inhibit platelet aggregation.

Simulation analysis of cascade controller for DC-DC bank converter

International Nuclear Information System (INIS)

Mahar, M.A.; Abro, M.R.; Larik, A.S.

2009-01-01

Power electronic converters are periodic variable structure systems due to their switched operation. During the last few decades several new dc-dc converter topologies have emerged. Buck converter being simple in topology, has recently drawn attraction of many researchers. Basically, a buck converter is highly underdamped system. In order to overcome the developed oscillations in output of this converter, various control techniques have been proposed. However, these techniques are fraught with many drawbacks. This paper focus on a cascade controller based buck topology. Steady state analysis is given in this paper which shows output voltage and inductor current in detail. Dynamic analysis for line and load variation is also presented. The buck topology is implemented and simulated in MATLAB/Simulink. The simulated results are presented. (author)

Bidirectional dc-to-dc Power Converter

Science.gov (United States)

Griesbach, C. R.

1986-01-01

Solid-state, series-resonant converter uses high-voltage thyristors. Converter used either to convert high-voltage, low-current dc power to lowvoltage, high current power or reverse. Taking advantage of newly-available high-voltage thyristors to provide better reliability and efficiency than traditional converters that use vacuum tubes as power switches. New converter essentially maintenance free and provides greatly increased mean time between failures. Attractive in industrial applications whether or not bidirectional capability is required.

Pulsed dc self-sustained magnetron sputtering

International Nuclear Information System (INIS)

Wiatrowski, A.; Posadowski, W. M.; Radzimski, Z. J.

2008-01-01

The magnetron sputtering has become one of the commonly used techniques for industrial deposition of thin films and coatings due to its simplicity and reliability. At standard magnetron sputtering conditions (argon pressure of ∼0.5 Pa) inert gas particles (necessary to sustain discharge) are often entrapped in the deposited films. Inert gas contamination can be eliminated during the self-sustained magnetron sputtering (SSS) process, where the presence of the inert gas is not a necessary requirement. Moreover the SSS process that is possible due to the high degree of ionization of the sputtered material also gives a unique condition during the transport of sputtered particles to the substrate. So far it has been shown that the self-sustained mode of magnetron operation can be obtained using dc powering (dc-SSS) only. The main disadvantage of the dc-SSS process is its instability related to random arc formation. In such case the discharge has to be temporarily extinguished to prevent damaging both the magnetron source and power supply. The authors postulate that pulsed powering could protect the SSS process against arcs, similarly to reactive pulsed magnetron deposition processes of insulating thin films. To put this concept into practice, (i) the high enough plasma density has to be achieved and (ii) the type of pulsed powering has to be chosen taking plasma dynamics into account. In this article results of pulsed dc self-sustained magnetron sputtering (pulsed dc-SSS) are presented. The planar magnetron equipped with a 50 mm diameter and 6 mm thick copper target was used during the experiments. The maximum target power was about 11 kW, which corresponded to the target power density of ∼560 W/cm 2 . The magnetron operation was investigated as a function of pulse frequency (20-100 kHz) and pulse duty factor (50%-90%). The discharge (argon) extinction pressure level was determined for these conditions. The plasma emission spectra (400-410 nm range) and deposition

Troubleshooting of Modulator DC power supply at KOMAC

Energy Technology Data Exchange (ETDEWEB)

Jeong, Hae Seong; Kim, Han Sung; Kwon, Hyeok Jung; Kim, Seong Gu; Kim, Dae Il; Lee, Seok Geun; Kim, Jae Ha; Seol, Kyeong Tae; Cho, Yong Sub [KAERI, Daejeon (Korea, Republic of)

2016-05-15

The process of solving problems to operate the 2nd converter modulator will be introduced. Also, the PSpice simulation result about the 12-pulse rectifier will be compared with the measurement result. KOMAC (KOrea Multi-purpose Accelerator Complex) has four HVCMs (High Voltage Converter Modulator) which are the power source of nine klystrons. Four HVCMs are already operated since 2013 for operating the 100 MeV linear proton accelerator at KOMAC. This HVCM system includes the 12-pulse rectifier (ac-dc), capacitors bank (dc-link, Pos, Neg) and converter modulator (dc-dc). Especially, the 12-pulse rectifier system receives the power from the utility and converts 3,300 ac voltage to 2,200 dc voltage for supplying the dc power to the capacitors bank. This rectifier system used twelve thyristors for the rectification and applied RC snubber networks to protect the semiconductor switches (thyristors). Since the 2nd modulator dc power supply has troubled, the troubleshooting process conducted by the staves of KOMAC. It takes 3 months to solve the problems because it is not easy to find the faulty wiring. Nevertheless, our staves found the faulty point with a hope to operate the modulator system and the PSpice simulation helps to solve the problems. Using PSpice which is tool for simulating the circuit, the dc power supply abnormal phenomenon was simulated exactly. After corrected the faulty wiring, the modulator dc power supply operated.

THE EVOLUTION OF DUSTY STAR FORMATION IN GALAXY CLUSTERS TO z = 1: SPITZER INFRARED OBSERVATIONS OF THE FIRST RED-SEQUENCE CLUSTER SURVEY

International Nuclear Information System (INIS)

Webb, T. M. A.; O'Donnell, D.; Coppin, Kristen; Faloon, Ashley; Geach, James E.; Noble, Allison; Yee, H. K. C.; Gilbank, David; Ellingson, Erica; Gladders, Mike; Muzzin, Adam; Wilson, Gillian; Yan, Renbin

2013-01-01

We present the results of an infrared (IR) study of high-redshift galaxy clusters with the MIPS camera on board the Spitzer Space Telescope. We have assembled a sample of 42 clusters from the Red-Sequence Cluster Survey-1 over the redshift range 0.3 14-15 M ☉ . We statistically measure the number of IR-luminous galaxies in clusters above a fixed inferred IR luminosity of 2 × 10 11 M ☉ , assuming a star forming galaxy template, per unit cluster mass and find it increases to higher redshift. Fitting a simple power-law we measure evolution of (1 + z) 5.1±1.9 over the range 0.3 cluster ). The evolution is similar, with ΣSFR/M cluster ∼ (1 + z) 5.4±1.9 . We show that this can be accounted for by the evolution of the IR-bright field population over the same redshift range; that is, the evolution can be attributed entirely to the change in the in-falling field galaxy population. We show that the ΣSFR/M cluster (binned over all redshift) decreases with increasing cluster mass with a slope (ΣSFR/M cluster ∼M cluster -1.5±0.4 ) consistent with the dependence of the stellar-to-total mass per unit cluster mass seen locally. The inferred star formation seen here could produce ∼5%-10% of the total stellar mass in massive clusters at z = 0, but we cannot constrain the descendant population, nor how rapidly the star-formation must shut-down once the galaxies have entered the cluster environment. Finally, we show a clear decrease in the number of IR-bright galaxies per unit optical galaxy in the cluster cores, confirming star formation continues to avoid the highest density regions of the universe at z ∼ 0.75 (the average redshift of the high-redshift clusters). While several previous studies appear to show enhanced star formation in high-redshift clusters relative to the field we note that these papers have not accounted for the overall increase in galaxy or dark matter density at the location of clusters. Once this is done, clusters at z ∼ 0.75 have the same

Geometry Optimization of DC/RF Photoelectron Gun

CERN Document Server

Chen Ping; Yu, David

2005-01-01

Pre-acceleration of photoelectrons in a pulsed, high voltage, short, dc gap and its subsequent injection into an rf gun is a promising method to improve electron beam emittance in rf accelerators. Simulation work has been performed in order to optimize the geometric shapes of a dc/rf gun and improve electron beam properties. Variations were made on cathode and anode shapes, dc gap distance, and inlet shape of the rf cavity. Simulations showed that significant improvement on the normalized emittance (< 1 mm-mrad), compared to a dc gun with flat cathode, could be obtained after the geometric shapes of the gun were optimized.

STAR FORMATION AND RELAXATION IN 379 NEARBY GALAXY CLUSTERS

International Nuclear Information System (INIS)

Cohen, Seth A.; Hickox, Ryan C.; Wegner, Gary A.

2015-01-01

We investigate the relationship between star formation (SF) and level of relaxation in a sample of 379 galaxy clusters at z < 0.2. We use data from the Sloan Digital Sky Survey to measure cluster membership and level of relaxation, and to select star-forming galaxies based on mid-infrared emission detected with the Wide-Field Infrared Survey Explorer. For galaxies with absolute magnitudes M r < −19.5, we find an inverse correlation between SF fraction and cluster relaxation: as a cluster becomes less relaxed, its SF fraction increases. Furthermore, in general, the subtracted SF fraction in all unrelaxed clusters (0.117 ± 0.003) is higher than that in all relaxed clusters (0.097 ± 0.005). We verify the validity of our SF calculation methods and membership criteria through analysis of previous work. Our results agree with previous findings that a weak correlation exists between cluster SF and dynamical state, possibly because unrelaxed clusters are less evolved relative to relaxed clusters

Modeling, Control and Protection of Low-Voltage DC Microgrids

OpenAIRE

Salomonsson, Daniel

2008-01-01

Current trends in electric power consumption indicate an increasing use of dc in end-user equipment, such as computers and other electronic appliances used in households and offices. With a dc power system, ac/dc conversion within these loads can be avoided, and losses reduced. AC/DC conversion is instead centralized, and by using efficient, fully controllable power-electronic interfaces, high power quality for both ac and dc systems during steady state and ac grid disturbances can be obtaine...

A ZVS PWM control strategy with balanced capacitor current for half-bridge three-level DC/DC converter

DEFF Research Database (Denmark)

Liu, Dong; Deng, Fujin; Chen, Zhe

2017-01-01

The capacitor current would be imbalanced under the conventional control strategy in the half-bridge three-level (HBTL) DC/DC converter due to the effect of the output inductance of the power supply and the input line inductance, which would affect the converter's reliability. This paper proposes...... a pulse-wide modulation (PWM) strategy composed of two operation modes for the HBTL DC/DC converter, which can realize the zero-voltage switching (ZVS) for the efficiency improvement. In addition, a capacitor current balancing control is proposed by alternating the two operation modes of the proposed ZVS...... PWM strategy, which can eliminate the current imbalance among the two input capacitors. Therefore, the proposed control strategy can improve the converter's performance and reliability in: 1) reducing the switching losses and noises of the power switches; 2) balancing the thermal stresses...

Synthetic properties of models of globular clusters

Energy Technology Data Exchange (ETDEWEB)

Angeletti, L; Dolcetta, R; Giannone, P. (Rome Univ. (Italy). Osservatorio Astronomico)

1980-05-01

Synthetic and projected properties of models of globular clusters have been computed on the basis of stellar evolution and time changes of the dynamical cluster structure. Clusters with five and eight stellar groups (each group consisting of stars with the same mass) were studied. Mass loss from evolved stars was taken into account. Observational features were obtained at ages of 10-19 x 10/sup 9/ yr. The basic importance of the horizontal- and asymptotic-branch stars was pointed out. A comparison of the results with observed data of M3 is discussed with the purpose of obtaining general indications rather than a specific fit.

Synthetic properties of models of globular clusters

International Nuclear Information System (INIS)

Angeletti, L.; Dolcetta, R.; Giannone, P.

1980-01-01

Synthetic and projected properties of models of globular clusters have been computed on the basis of stellar evolution and time changes of the dynamical cluster structure. Clusters with five and eight stellar groups (each group consisting of stars with the same mass) were studied. Mass loss from evolved stars was taken into account. Observational features were obtained at ages of 10-19 x 10 9 yr. The basic importance of the horizontal- and asymptotic-branch stars was pointed out. A comparison of the results with observed data of M3 is discussed with the purpose of obtaining general indications rather than a specific fit. (orig.)

Clustering of near clusters versus cluster compactness

International Nuclear Information System (INIS)

Yu Gao; Yipeng Jing

1989-01-01

The clustering properties of near Zwicky clusters are studied by using the two-point angular correlation function. The angular correlation functions for compact and medium compact clusters, for open clusters, and for all near Zwicky clusters are estimated. The results show much stronger clustering for compact and medium compact clusters than for open clusters, and that open clusters have nearly the same clustering strength as galaxies. A detailed study of the compactness-dependence of correlation function strength is worth investigating. (author)

Novel family of quasi-Z-source DC/DC converters derived from current-fed push-pull converters

DEFF Research Database (Denmark)

Chub, Andrii; Husev, Oleksandr; Vinnikov, Dmitri

2014-01-01

This paper is devoted to the step-up quasi-Z-source dc/dc push-pull converter family. The topologies in the family are derived from the isolated boost converter family by replacing input inductors with the quasi-Z-source network. Two new topologies are proposed, analyzed and compared. Theoretical...

75 FR 35611 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, and MD-10-10F...

Science.gov (United States)

2010-06-23

... Airworthiness Directives; McDonnell Douglas Corporation Model DC- 10-10, DC-10-10F, and MD-10-10F Airplanes... certain McDonnell Douglas Model DC-10-10, DC-10-10F, and MD-10-10F airplanes. That NPRM was published in... amends Sec. 39.13 by adding the following new AD: 2010-13-06 McDonnell Douglas Corporation: Amendment 39...

Active superconducting DC fault current limiter based on flux compensation

International Nuclear Information System (INIS)

Shi Jing; Tang Yuejin; Wang, Chen; Zhou Yusheng; Li Jingdong; Ren Li; Chen Shijie

2006-01-01

With the extensive application of DC power systems, suppression of DC fault current is an important subject that guarantees system security. This paper presents an active superconducting DC fault current limiter (DC-SFCL) based on flux compensation. The DC-SFCL is composed of two superconducting windings wound on a single iron core, the primary winding is in series with DC power system, and the second winding is connected with AC power system through a PWM converter. In normal operating state, the flux in the iron core is compensated to zero, and the SFCL has no influence on DC power system. In the case of DC system accident, through regulating the active power exchange between the SFCL's second winding and the AC power system, the current on the DC side can be limited to different level complying with the system demand. Moreover, the PWM converter that interface the DC system and AC system can be controlled as a reactive power source to supply voltage support for the AC side, which has little influence on the performance of SFCL. Using MATLAB SIMULINK, the mathematic model of the DC-SFCL is created, simulation results validate the dynamics of system, and the performance of DC-SFCL is confirmed

A Decentralized Current-Sharing Controller Endows Fast Transient Response to Parallel DC-DC Converters

DEFF Research Database (Denmark)

Wang, Haojie; Han, Minxiao; Han, Renke

2018-01-01

This paper proposes a decentralized current-sharing control strategy to endow fast transient response to paralleled DC-DC converters systems, such as DC microgrids or distributed power systems. The proposed controller consist of two main control loops: an external voltage droop control for current......-sharing proposes and an internal current loop. The external droop control loop is designed as a voltage loop with embedded virtual impedance, which avoids the use of a slow voltage loop and a separate extra virtual impedance loop that may limit the system bandwidth. The internal current loop, thanks...... and the proposed embedded-virtual-impedance based I-V droop. In order to compare the dynamic response performances between two droop controllers, their state-space models have been developed and analyzed in this paper. The results show that the dynamic response of the I-V droop control is faster than...

A Reconfigurable Series Resonant DC-DC Converter for Wide-Input and Wide-Output Voltages

DEFF Research Database (Denmark)

Shen, Yanfeng; Wang, Huai; Qin, Zian

2017-01-01

This paper proposes a dual-bridge based LC series resonant dc-dc converter. The input inverter unit incorporates two bridge structures, i.e., a full-bridge inverter and a half-bridge inverter. For the output rectifier, it can be a full-bridge rectifier or an asymmetric half-bridge rectifier....... Different from the conventional resonant converter, a fixed-frequency PWM control is employed which makes the optimization of magnetic components easier. The primary-side switches can achieve ZVS and the secondary-side diodes turn off with ZCS. In addition, the root-mean-square (RMS) values...... of the transformer currents do not significantly vary with respect to the voltage variation. Therefore, this converter can maintain high efficiency over a wide voltage range. The topology and operating principle are firstly described. Then the dc voltage gain and the RMS current characteristics are detailed. Finally...

Proceedings of the American Psychological Association for the Legislative Year 2006: Minutes of the Annual Meeting of the Council of Representatives, February 17-19, 2006, Washington, DC; and August 17 and 21, 2006, New Orleans, LA; and Minutes of the February, June, August, and December 2006 Meetings of the Board of Directors

Science.gov (United States)

Paige, Ruth Ullmann

2007-01-01

Minutes of the Annual Meeting of the Council of Representatives (February 17-19, 2006, Washington, DC; and August 17 and 21, 2006, New Orleans, LA) and of the 2006 meetings of the Board of Directors (February, June, August, and December) are provided. These minutes are the official record of the actions of the American Psychological Association…

Cluster-cluster clustering

International Nuclear Information System (INIS)

Barnes, J.; Dekel, A.; Efstathiou, G.; Frenk, C.S.; Yale Univ., New Haven, CT; California Univ., Santa Barbara; Cambridge Univ., England; Sussex Univ., Brighton, England)

1985-01-01

The cluster correlation function xi sub c(r) is compared with the particle correlation function, xi(r) in cosmological N-body simulations with a wide range of initial conditions. The experiments include scale-free initial conditions, pancake models with a coherence length in the initial density field, and hybrid models. Three N-body techniques and two cluster-finding algorithms are used. In scale-free models with white noise initial conditions, xi sub c and xi are essentially identical. In scale-free models with more power on large scales, it is found that the amplitude of xi sub c increases with cluster richness; in this case the clusters give a biased estimate of the particle correlations. In the pancake and hybrid models (with n = 0 or 1), xi sub c is steeper than xi, but the cluster correlation length exceeds that of the points by less than a factor of 2, independent of cluster richness. Thus the high amplitude of xi sub c found in studies of rich clusters of galaxies is inconsistent with white noise and pancake models and may indicate a primordial fluctuation spectrum with substantial power on large scales. 30 references

Modelling, simulation and construction of a dc/dc boost power converter: a school experimental system

International Nuclear Information System (INIS)

Silva-Ortigoza, R; Marciano-Melchor, M; Silva-Ortigoza, G; Hernández-Guzmán, V M; Saldaña-González, G; Marcelino-Aranda, M

2012-01-01

We introduce a dc/dc boost power converter as a didactic prototype intended to support courses on electric circuit analysis experimentally. The corresponding mathematical model is obtained, the converter is designed and an experimental setup is described, constructed and tested. Simplicity of construction as well as low cost of components renders the feasible introduction of this equipment in undergraduate laboratories. (paper)

Security analysis of interconnected AC/DC systems

DEFF Research Database (Denmark)

Eriksson, Robert

2015-01-01

This paper analyses N-1 security in an interconnected ac/dc transmission system using power transfer distribution factors (PTDFs). In the case of a dc converter outage the power needs to be redistributed among the remaining converter to maintain power balance and operation of the dc grid...... any line or transformer limits. Simulations were performed in a model of the Nordic power system where a dc grid is placed on top. The simulation supports the method as a tool to consider transfer limits in the grid to avoid violate the same and increase the security after a converter outage........ The redistribution of power has a sudden effect on the power-flow in the interconnected ac system. This may cause overloading of lines and transformers resulting in disconnection of equipment, and as a consequence cascading failure. The PTDF is used as a method to analyze and avoid violating limits by in the dc...

Systematic design approach of fuzzy PID stabilizer for DC-DC converters

International Nuclear Information System (INIS)

Guesmi, K.; Essounbouli, N.; Hamzaoui, A.

2008-01-01

DC-DC converters process electrical energy by switching between a fixed number of configurations. The objective of controlling these systems is to provide better performances, ensure closed loop stability and guarantee a simple predictable behaviour. Based on a converter averaged model, we propose, in this paper, a systematic design approach of a fuzzy PID. The choice of controller parameters stands on the whole system stability requirements. Extension of the obtained asymptotic stability to structural stability is presented to show that the developed controller ensures also a simple and predictable behaviour of the converter. Finally, we illustrate the efficiency of the proposed fuzzy PID design approach through simulations in voltage mode as well as in current mode control

Systematic design approach of fuzzy PID stabilizer for DC-DC converters

Energy Technology Data Exchange (ETDEWEB)

Guesmi, K.; Essounbouli, N.; Hamzaoui, A. [CReSTIC, IUT de Troyes 09, rue de Quebec BP. 396, 10026 Troyes (France)

2008-10-15

DC-DC converters process electrical energy by switching between a fixed number of configurations. The objective of controlling these systems is to provide better performances, ensure closed loop stability and guarantee a simple predictable behaviour. Based on a converter averaged model, we propose, in this paper, a systematic design approach of a fuzzy PID. The choice of controller parameters stands on the whole system stability requirements. Extension of the obtained asymptotic stability to structural stability is presented to show that the developed controller ensures also a simple and predictable behaviour of the converter. Finally, we illustrate the efficiency of the proposed fuzzy PID design approach through simulations in voltage mode as well as in current mode control. (author)

Deadbeat control of power leveling unit with bidirectional buck/boost DC/DC converter

OpenAIRE

Hamasaki, Shin-ichi; Mukai, Ryosuke; Yano, Yoshihiro; Tsuji, Mineo

2014-01-01

As a distributed generation system increases, a stable power supply becomes difficult. Thus control of power leveling (PL) unit is required to maintain the balance of power flow for irregular power generation. The unit is required to respond to change of voltage and bidirectional power flow. So the bidirectional buck/boost DC/DC converter is applied for the control of PL unit in this research. The PL unit with Electric double-layer capacitor (EDLC) is able to absorb change of power, and it is...

Conducted EMI Prediction and Mitigation Strategy Based on Transfer Function for a High-Low Voltage DC-DC Converter in Electric Vehicle

Directory of Open Access Journals (Sweden)

Li Zhai

2018-04-01

Full Text Available The high dv/dt and di/dt outputs from power devices in a high-low voltage DC-DC converter on electric vehicles (EVs can always introduce the unwanted conducted electromagnetic interference (EMI emissions. A conducted EMI prediction and mitigation strategy that is based on transfer function for the high-low voltage DC-DC converter in EVs are proposed. A complete test for the DC-DC converter is conducted to obtain the conducted EMI from DC power cables in the frequency band of 150 kHz-108 MHz. The equivalent circuit with high-frequency parasitic parameters of the DC-DC converter is built`1 based on the measurement results to acquire the characteristics of the conducted EMI of the DC power cables. The common mode (CM and differential mode (DM propagation coupling paths are determined, and the corresponding transfer functions of the DM interference and CM interference are established. The simulation results of the conducted EMI can be obtained by software Matlab and Computer Simulation Technology (CST. By analyzing the transfer functions and the simulation results, the dominated interference is the CM interference, which is the main factor of the conducted EMI. A mitigation strategy for the design of the CM interference filter based on the dominated CM interference is proposed. Finally, the mitigation strategy of the conducted EMI is verified by performing the conducted voltage experiment. From the experiment results, the conducted voltage of the DC power cables is decreased, respectively, by 58 dBμV, 55 dBμV, 65 dBμV, 53 dBμV, and 54 dBμV at frequency 200 kHz, 400 kHz, 600 kHz, 1.4 MHz, and 50 MHz. The conduced voltage in the frequency band of 150 kHz–108 MHz can be mitigated by adding the CM interference filters, and the values are lower than the limit level-3 of CISPR25 standard (GB/T 18655-2010.

Comparative efficiency evaluation of buck and hybrid buck DC-DC converters for automotive applications

DEFF Research Database (Denmark)

Pelan, Ovidiu; Cornea, Octavian; Muntean, Nicolae

2014-01-01

This paper presents and discusses design considerations and efficiency investigation of a conventional step-down and a hybrid switched-capacitor DC-DC converter. Three MOSFETs with low on-resistance have been tested for each converter in order to find the most adequate switch for this application....... The experimental results and comparative efficiency graphs were obtained with a 1kW laboratory prototype dedicated for a 42/14V dual voltage automotive system....

MEDOW - Multi-terminal DC Grid for Offshore Wind, Final report

DEFF Research Database (Denmark)

A DC grid based on multi-terminal voltage-source converter is a newly emerging technology, which is particularly suitable for the connection of offshore wind farms. Multi-terminal DC grids will be the key technology for the European offshore ‘Super Grid’. In the project, DC power flow, DC relaying...... protection, steady state operation, dynamic stability, fault-ride through capability, and impacts of DC grids on the operation of AC grids and power market were studied. Systematic comparison of DC grid topologies and stability control strategies was carried out, and DC grids for offshore wind power...

Kingsnorth-London dc transmission link

Energy Technology Data Exchange (ETDEWEB)

1966-03-11

The hvdc transmission link between one of the 500 MW generators at Kingsnorth Power Station and two receiving stations in London will use a three-wire dc cable system rated to carry 1200 A at +- 266 kV. This 51-mile system will be the first dc link in the world to be used as an integral part of a complex interconnected ac network.

Dual wound dc brush motor gearhead

Science.gov (United States)

Henson, Barrie W.

1986-01-01

The design requirements, the design, development tests and problems, the qualification and life test and the findings of the strip examination of a dual wound DC brushed motor gearhead are described. It is the only space qualified dual wound dc brushed motor gearhead in Europe.

Analysis and Controller Design of a Universal Bidirectional DC-DC Converter

Directory of Open Access Journals (Sweden)

Kou-Bin Liu

2016-06-01

Full Text Available In this paper, first the operating principles of a non-isolated universal bidirectional DC-DC converter are studied and analyzed. The presented power converter is capable of operating in all power transferring directions in buck/boost modes. Zero voltage switching can be achieved for all the power switches through proper modulation strategy design, therefore, the presented converter can achieve high efficiency. To further improve the efficiency, the relationship between the phase-shift angle and the overall system efficiency is analyzed in detail, an adaptive phase-shift (APS control method which determines the phase-shift value between gating signals according to the load level is then proposed. As the modulation strategy is a software-based solution, there is no requirement for additional circuits, therefore, it can be implemented easily and instability and noise susceptibility problems can be reduced. To validate the correctness and the effectiveness of the proposed method, a 300 W prototyping circuit is implemented and tested. A low cost dsPIC33FJ16GS502 digital signal controller is adopted in this paper to realize the power flow control, DC-bus voltage regulation and APS control. According to the experimental results, a 12.2% efficiency improvement at light load and 4.0% efficiency improvement at half load can be achieved.

Drilling history core hole DC-6 Hanford, Washington

International Nuclear Information System (INIS)

1978-06-01

Core hole DC-6 was completed in May 1978 by Boyles Brothers Drilling Company, Spokane, Washington, under subcontract to Fenix and Scisson, Inc. The hole was cored for the US Department of Energy and the Rockwell Hanford Operations' Basalt Waste Isolation Program. Fenix and Scisson, Inc. furnished the engineering, daily supervision of the core drilling activities, and geologic core logging for hole DC-6. Core hole DC-6 is located within the boundary of the Hanford Site at the old Hanford town site. The Hanford Site coordinates for DC-6 are North 54,127.17 feet and West 17,721.00 feet. The surface elevation is approximately 402 feet above sea level. The purpose of core hole DC-6 was to core drill vertically through the basalt and interbed units for stratigraphic depth determination and core collection and to provide a borehole for hydrologic testing. The total depth of core hole DC-6 was 4336 feet. Core recovery was 98.4% of the total footage cored

FPGA implementation of optimal and approximate model predictive control for a buck-boost DC-DC converter

NARCIS (Netherlands)

Spinu, V.; Oliveri, A.; Lazar, M.; Storace, M.

2012-01-01

This paper proposes a method for FPGA implementation of explicit, piecewise af¿ne (PWA) model predictive control (MPC) laws for non-inverting buck-boost DC-DC converters. A novel approach to obtain a PWA model of the power converter is proposed and two explicit MPC laws are derived, i.e., one based

Research & Implementation of AC - DC Converter with High Power Factor & High Efficiency

Directory of Open Access Journals (Sweden)

Hsiou-Hsian Nien

2014-05-01

Full Text Available In this paper, we design and develop a high power factor, high efficiency two-stage AC - DC power converter. This paper proposes a two-stage AC - DC power converter. The first stage is boost active power factor correction circuit. The latter stage is near constant frequency LLC resonant converter. In addition to traditional LLC high efficiency advantages, light-load conversion efficiency of this power converter can be improved. And it possesses high power factor and near constant frequency operating characteristics, can significantly reduce the electromagnetic interference. This paper first discusses the main structure and control manner of power factor correction circuit. And then by the LLC resonant converter equivalent model proceed to circuit analysis to determine the important parameters of the converter circuit elements. Then design a variable frequency resonant tank. The resonant frequency can change automatically on the basis of the load to reach near constant frequency operation and a purpose of high efficiency. Finally, actually design and produce an AC – DC power converter with output of 190W to verify the characteristics and feasibility of this converter. The experimental results show that in a very light load (9.5 W the efficiency is as high as 81%, the highest efficiency of 88% (90 W. Full load efficiency is 87%. At 19 W ~ 190 W power changes, the operating frequency change is only 0.4 kHz (AC 110 V and 0.3 kHz (AC 220 V.

Closed-cage tungsten oxide clusters in the gas phase.

Science.gov (United States)

Singh, D M David Jeba; Pradeep, T; Thirumoorthy, Krishnan; Balasubramanian, Krishnan

2010-05-06

During the course of a study on the clustering of W-Se and W-S mixtures in the gas phase using laser desorption ionization (LDI) mass spectrometry, we observed several anionic W-O clusters. Three distinct species, W(6)O(19)(-), W(13)O(29)(-), and W(14)O(32)(-), stand out as intense peaks in the regular mass spectral pattern of tungsten oxide clusters suggesting unusual stabilities for them. Moreover, these clusters do not fragment in the postsource decay analysis. While trying to understand the precursor material, which produced these clusters, we found the presence of nanoscale forms of tungsten oxide. The structure and thermodynamic parameters of tungsten clusters have been explored using relativistic quantum chemical methods. Our computed results of atomization energy are consistent with the observed LDI mass spectra. The computational results suggest that the clusters observed have closed-cage structure. These distinct W(13) and W(14) clusters were observed for the first time in the gas phase.

Stability analysis of a three-phase grid-connected DC power supply with small DC-link capacitor and voltage feed-forward compensation

DEFF Research Database (Denmark)

Török, Lajos; Mathe, L.

2017-01-01

The purpose of this work was to investigate effect of the DC-link voltage feed-forward compensation on the stability of the three-phase-grid connected DC power supply, used for electrolysis application, equipped with small DC link capacitor. In case of weak grid condition, the system...

Identifying seizure clusters in patients with psychogenic nonepileptic seizures.

Science.gov (United States)

Baird, Grayson L; Harlow, Lisa L; Machan, Jason T; Thomas, Dave; LaFrance, W C

2017-08-01

The present study explored how seizure clusters may be defined for those with psychogenic nonepileptic seizures (PNES), a topic for which there is a paucity of literature. The sample was drawn from a multisite randomized clinical trial for PNES; seizure data are from participants' seizure diaries. Three possible cluster definitions were examined: 1) common clinical definition, where ≥3 seizures in a day is considered a cluster, along with two novel statistical definitions, where ≥3 seizures in a day are considered a cluster if the observed number of seizures statistically exceeds what would be expected relative to a patient's: 1) average seizure rate prior to the trial, 2) observed seizure rate for the previous seven days. Prevalence of clusters was 62-68% depending on cluster definition used, and occurrence rate of clusters was 6-19% depending on cluster definition. Based on these data, clusters seem to be common in patients with PNES, and more research is needed to identify if clusters are related to triggers and outcomes. Copyright © 2017 Elsevier Inc. All rights reserved.

Design and Implementation of Battery Charger with Power Factor Correction using Sepic Converter and Full-bridge DC-DC Converter

Directory of Open Access Journals (Sweden)

Moh. Zaenal Efendi

2013-12-01

Full Text Available This paper presents a design and implementation of a converter which has a high power factor for battery charger application. The converter is a combination of a SEPIC converter and a full-bridge DC-DC converter connected in two stages of series circuit. The SEPIC converter works in discontinuous conduction mode and it serves as a power factor corrector so that the shape of input current waveform follows the shape of input voltage waveform. The full-bridge DC-DC converter serves as a regulator of output voltage and operates at continuous conduction mode. The experimental results show that the power factor of this converter system can be achieved up to 0.96.

Modified High Voltage Conversion Inverting Cuk DC-DC Converter for Renewable Energy Application

DEFF Research Database (Denmark)

Maroti, Pandav Kiran; Padmanaban, Sanjeevikumar; Wheeler, Patrick

2017-01-01

controlled device DC-DC topology. The voltage conversion ratio of proposed converter has increased by ten times of the conventional Cuk converterat a duty ratio of 90%. The detailed analysis of the voltage conversion ratio and losses occur due to internal resistance of components is done in the paper......The proposed exertion represents the modified high voltage conversion Cuk converter for renewable energy application. The proposed Cuk converter is a combination of the conventional boost converter and Cuk converter. The arrangement of the proposed converter make, such as, it becomes the single...

A DC Transformer

Data.gov (United States)

National Aeronautics and Space Administration — The goal of the project was to demonstrate a true direct current (DC) transformer, a new electro-mechanical component with potentially high power applications; in...

Unregulated Series Resonant Converter for Interlinking DC Nanogrids

DEFF Research Database (Denmark)

Tomas Manez, Kevin; Zhang, Zhe; Ouyang, Ziwei

2017-01-01

bidirectional converter to interlink a 400V DC bus with a 48V DC bus ispresented. The proposed converter is based on a LLC resonant converter operating as a DC transformer at a fixed frequency and duty cycle without any complex control strategy. A clearand simplified design procedure for high efficiency...

High voltage dc-dc converter with dynamic voltage regulation and decoupling during load-generated arcs

Science.gov (United States)

Shimer, Daniel W.; Lange, Arnold C.

1995-01-01

A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules.

High voltage dc--dc converter with dynamic voltage regulation and decoupling during load-generated arcs

Science.gov (United States)

Shimer, D.W.; Lange, A.C.

1995-05-23

A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules. 5 Figs.

Codebook Generation Using Partition and Agglomerative Clustering

Directory of Open Access Journals (Sweden)

CHANG, C.-T.

2011-08-01

Full Text Available In this paper, we present a codebook generation algorithm to produce a codebook with lower distortion. Our method combines a fast codebook generation algorithm (CGAUCD with doubling technique and fast agglomerative clustering algorithm (FACA to generate a codebook with less computing time and lower distortion. Instead of using FACA directly to divide training vectors into M clusters, our proposed method first generates qM clusters from these training vectors, where q>1 is an integer, and then applies FACA to merge these qM clusters into M cells. This is due to the computational complexity of CGAUCD with doubling technique is less than that of FACA. These M cluster centers are used as the initial codebook for CGAUCD. Using three real images as the training set, our method can reduce the MSE and computing time of FPNN+CGAUCD, which is the available best method to our knowledge, by 0.19 to 0.38 and 74.6% to 84.3%, respectively.

DC-DC Converter Topology Assessment for Large Scale Distributed Photovoltaic Plant Architectures

Energy Technology Data Exchange (ETDEWEB)

Agamy, Mohammed S; Harfman-Todorovic, Maja; Elasser, Ahmed; Sabate, Juan A; Steigerwald, Robert L; Jiang, Yan; Essakiappan, Somasundaram

2011-07-01

Distributed photovoltaic (PV) plant architectures are emerging as a replacement for the classical central inverter based systems. However, power converters of smaller ratings may have a negative impact on system efficiency, reliability and cost. Therefore, it is necessary to design converters with very high efficiency and simpler topologies in order not to offset the benefits gained by using distributed PV systems. In this paper an evaluation of the selection criteria for dc-dc converters for distributed PV systems is performed; this evaluation includes efficiency, simplicity of design, reliability and cost. Based on this evaluation, recommendations can be made as to which class of converters is best fit for this application.

SSP Technology Investigation of a High-Voltage DC-DC Converter

Science.gov (United States)

Pappas, J. A.; Grady, W. M.; George, Patrick J. (Technical Monitor)

2002-01-01

The goal of this project was to establish the feasibility of a high-voltage DC-DC converter based on a rod-array triggered vacuum switch (RATVS) for the Space Solar Power system. The RATVS has many advantages over silicon and silicon-carbide devices. The RATVS is attractive for this application because it is a high-voltage device that has already been demonstrated at currents in excess of the requirement for an SSP device and at much higher per-device voltages than existing or near-term solid state switching devices. The RATVS packs a much higher specific power rating than any solid-state device and it is likely to be more tolerant of its surroundings in space. In addition, pursuit of an RATVS-based system would provide NASA with a nearer-term and less expensive power converter option for the SSP.

DC-Evoked Modulation of Excitability of Myelinated Nerve Fibers and Their Terminal Branches; Differences in Sustained Effects of DC.

Science.gov (United States)

Kaczmarek, Dominik; Jankowska, Elzbieta

2018-03-15

Direct current (DC) evokes long-lasting changes in neuronal networks both presynaptically and postsynaptically and different mechanisms were proposed to be involved in them. Different mechanisms were also suggested to account for the different dynamics of presynaptic DC actions on myelinated nerve fibers stimulated before they entered the spinal gray matter and on their terminal branches. The aim of the present study was to examine whether these different dynamics might be related to differences in the involvement of K + channels. To this end, we compared effects of the K + channel blocker 4-amino-pyridine (4-AP) on DC-evoked changes in the excitability of afferent fibers stimulated within the dorsal columns (epidurally) and within their projection areas in the dorsal horn and motor nuclei (intraspinally). 4-AP was applied systemically in deeply anesthetized rats. DC-evoked increases in the excitability of epidurally stimulated afferent nerve fibers, and increases in field potentials evoked by these fibers, were not affected by 4-AP. In contrast, sustained decreases rather than increases in the excitability of intraspinally stimulated terminal nerve branches were evoked by local application of DC in conjunction with 4-AP. The study leads to the conclusion that 4-AP-sensitive K + channels contribute to the sustained DC-evoked post-polarization increases in the excitability at the level of terminal branches of nerve fibers but not of the nodes of Ranvier nor within the juxta-paranodal regions where other mechanisms would be involved in inducing the sustained DC-evoked changes. Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.

Predictive Trailing-Edge Modulation Average Current Control in DC-DC Converters

Directory of Open Access Journals (Sweden)

LASCU, D.

2013-11-01

Full Text Available The paper investigates predictive digital average current control (PDACC in dc/dc converters using trailing-edge modulation (TEM. The study is focused on the recurrence duty cycle equation and then stability analysis is performed. It is demonstrated that average current control using trailing-edge modulation is stable on the whole range of the duty cycle and thus design problems are highly reduced. The analysis is carried out in a general manner, independent of converter topology and therefore the results can then be easily applied for a certain converter (buck, boost, buck-boost, etc.. The theoretical considerations are confirmed for a boost converter first using the MATLAB program based on state-space equations and finally with the CASPOC circuit simulation package.

Control of hybrid AC/DC microgrid under islanding operational conditions

DEFF Research Database (Denmark)

Ding, G.; Gao, F.; Zhang, S.

2014-01-01

This paper presents control methods for hybrid AC/DC microgrid under islanding operation condition. The control schemes for AC sub-microgrid and DC sub-microgrid are investigated according to the power sharing requirement and operational reliability. In addition, the key control schemes...... of interlinking converter with DC-link capacitor or energy storage, which will devote to the proper power sharing between AC and DC sub-microgrids to maintain AC and DC side voltage stable, is reviewed. Combining the specific control methods developed for AC and DC sub-microgrids with interlinking converter......, the whole hybrid AC/DC microgrid can manage the power flow transferred between sub-microgrids for improving on the operational quality and efficiency....

Clusters of Multidrug-Resistant Mycobacterium tuberculosis Cases, Europe

Science.gov (United States)

Kremer, Kristin; Heersma, Herre; Van Soolingen, Dick

2009-01-01

Molecular surveillance of multidrug-resistant tuberculosis (MDR TB) was implemented in Europe as case reporting in 2005. For all new MDR TB cases detected from January 2003 through June 2007, countries reported case-based epidemiologic data and DNA fingerprint patterns of MDR TB strains when available. International clusters were detected and analyzed. From 2003 through mid-2007 in Europe, 2,494 cases of MDR TB were reported from 24 European countries. Epidemiologic and molecular data were linked for 593 (39%) cases, and 672 insertion sequence 6110 DNA fingerprint patterns were reported from 19 countries. Of these patterns, 288 (43%) belonged to 18 European clusters; 7 clusters (242/288 cases, 84%) were characterized by strains of the Beijing genotype family, including the largest cluster (175/288 cases, 61%). Both clustering and the Beijing genotype were associated with strains originating in eastern European countries. Molecular cluster detection contributes to identification of transmission profile, risk factors, and control measures. PMID:19624920

Analisa Perbandingan Efisiensi Motor Dc Kompon Pendek Dengan Motor Dc Kompon Panjang Akibat Penambahan Kutub

OpenAIRE

Sitompul, Fuad Rahim

2015-01-01

Motor listrik merupakan perangkat elekromagnetis yang mengubah energi listrik menjadi energi mekanik. Motor DC memerlukan tegangan searah pada kumparan medan untuk diubah menjadi energi mekanik. Energi mekanik ini digunakan sebagai penggerak peralatan listrik seperti pompa,penggerak kipas angin, lift dan lain-lain. Karena penggunaannya yang cukup luas maka kinerjanya harus baik. Kinerja suatu motor DC dikatakan baik jika efisiensi motor tersebut tinggi. Hal itu dapat dicapai dengan mengatur b...

A soft-switching coupled inductor bidirectional DC-DC converter with high-conversion ratio

Science.gov (United States)

Chao, Kuei-Hsiang; Jheng, Yi-Cing

2018-01-01

A soft-switching bidirectional DC-DC converter is presented herein as a way to improve the conversion efficiency of a photovoltaic (PV) system. Adoption of coupled inductors enables the presented converter not only to provide a high-conversion ratio but also to suppress the transient surge voltage via the release of the energy stored in leakage flux of the coupled inductors, and the cost can kept down consequently. A combined use of a switching mechanism and an auxiliary resonant branch enables the converter to successfully perform zero-voltage switching operations on the main switches and improves the efficiency accordingly. It was testified by experiments that our proposed converter works relatively efficiently in full-load working range. Additionally, the framework of the converter intended for testifying has high-conversion ratio. The results of a test, where a generating system using PV module array coupled with batteries as energy storage device was used as the low-voltage input side, and DC link was used as high-voltage side, demonstrated our proposed converter framework with high-conversion ratio on both high-voltage and low-voltage sides.

Solar Photovoltaic DC Systems: Basics and Safety: Preprint

Energy Technology Data Exchange (ETDEWEB)

McNutt, Peter F [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sekulic, William R [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Dreifuerst, Gary [Lawrence Livermore National Laboratory - retired

2018-04-02

Solar Photovoltaic (PV) systems are common and growing with 42.4 GW installed capacity in U.S. (almost 15 GW added in 2016). This paper will help electrical workers, and emergency responders understand the basic operating principles and hazards of PV DC arrays. We briefly discuss the following aspects of solar photovoltaic (PV) DC systems: the effects of solar radiation and temperature on output power; PV module testing standards; common system configurations; a simple PV array sizing example; NEC guidelines and other safety features; DC array commissioning, periodic maintenance and testing; arc-flash hazard potential; how electrical workers and emergency responders can and do work safely around PV arrays; do moonlight and artificial lighting pose a real danger; typical safe operating procedures; and other potential DC-system hazards to be aware of. We also present some statistics on PV DC array electrical incidents and injuries. Safe PV array operation is possible with a good understanding of PV DC arrays basics and having good safe operating procedures in place.

Digital DC beam current measurement on SSRF storage ring

International Nuclear Information System (INIS)

Xiong Liang; Yin Chongxian; Liu Ming; Chen Jianfeng

2011-01-01

Both DC current transformer (DCCT) and integrating current transformer (ICT) can be used in DC beam current measurement. The ICT has strong capability of resisting electromagnetic interference, but its measurement accuracy cannot satisfy the DC beam current measurement requirement when using traditional high speed A/D. With high resolution A/D and equivalent sampling system, DC beam current measuring system based on ICT can reach high accuracy compared with DCCT system. In this paper, the ICT-based DC beam current measurement, equivalent sampling method and testing results at Shanghai Synchrotron Radiation Facility(SSRF) is described. (authors)

Star clusters and K2

Science.gov (United States)

Dotson, Jessie; Barentsen, Geert; Cody, Ann Marie

2018-01-01

The K2 survey has expanded the Kepler legacy by using the repurposed spacecraft to observe over 20 star clusters. The sample includes open and globular clusters at all ages, including very young (1-10 Myr, e.g. Taurus, Upper Sco, NGC 6530), moderately young (0.1-1 Gyr, e.g. M35, M44, Pleiades, Hyades), middle-aged (e.g. M67, Ruprecht 147, NGC 2158), and old globular clusters (e.g. M9, M19, Terzan 5). K2 observations of stellar clusters are exploring the rotation period-mass relationship to significantly lower masses than was previously possible, shedding light on the angular momentum budget and its dependence on mass and circumstellar disk properties, and illuminating the role of multiplicity in stellar angular momentum. Exoplanets discovered by K2 in stellar clusters provides planetary systems ripe for modeling given the extensive information available about their ages and environment. I will review the star clusters sampled by K2 across 16 fields so far, highlighting several characteristics, caveats, and unexplored uses of the public data set along the way. With fuel expected to run out in 2018, I will discuss the closing Campaigns, highlight the final target selection opportunities, and explain the data archive and TESS-compatible software tools the K2 mission intends to leave behind for posterity.

Method to predetermine current/power flow change in a dc grid

DEFF Research Database (Denmark)

2017-01-01

occurs at one of the AC/DC converters; establishing a generalized droop feedback gain matrix G; controlling current/power flow within DC grid towards predefined setpoints, by use of control law. The invention presents an analytical approach to derive the generalized feedback gain allowing......The invention relates to a method for controlling current/power flow within a power transmission system, comprising two or more interconnected converter stations. The method comprises the steps of: providing a DC admittance matrix given from the DC grid; providing a current distribution matrix...... for a number of, such as for all possible AC/DC converter outages; providing a DC bus voltage vector for the DC grid; the DC bus voltage vector being a vector containing the values of the voltage change at the AC/DC converters, measured at the AC/DC converters, before, during and after a forced current change...

Development of AC-DC power system simulator

International Nuclear Information System (INIS)

Ichikawa, Tatsumi; Ueda, Kiyotaka; Inoue, Toshio

1984-01-01

A modeling and realization technique is described for realtime plant dynamics simulation of nuclear power generating unit in AC-DC power system simulator. Dynamic behavior of reactor system and steam system is important for investigation a further adequate unit control and protection system to system faults in AC and DC power system. Each unit of two nuclear power generating unit in the power system simulator consists of micro generator, DC motors, flywheels and process computer. The DC motor and flywheel simulates dynamic characteristics of steam turbine, and process computer simulates plant dynamics by digital simulation. We have realized real-time plant dynamics simulation by utilizing a high speed process I/O and a high speed digital differential analyzing processor (DDA) in which we builted a newly developed simple plant model. (author)

Modeling and simulation for micro DC motor based on simulink

Science.gov (United States)

Shen, Hanxin; Lei, Qiao; Chen, Wenxiang

2017-09-01

The micro DC motor has a large market demand but there is a lack of theoretical research for it. Through detailed analysis of the commutation process of micro DC motor commutator, based on micro DC motor electromagnetic torque equation and mechanical torque equation, with the help of Simulink toolkit, a triangle connection micro DC motor simulation model is established. By using the model, a sample micro DC motor are simulated, and an experimental measurements has been carried on the sample micro DC motor. It is found that the simulation results are consistent with theoretical analysis and experimental results.

Comparison of two different high performance mixed signal controllers for DC/DC converters

DEFF Research Database (Denmark)

Jakobsen, Lars Tønnes; Andersen, Michael Andreas E.

2006-01-01

This paper describes how mixed signal controllers combining a cheap microcontroller with a simple analogue circuit can offer high performance digital control for DC/DC converters. Mixed signal controllers have the same versatility and performance as DSP based controllers. It is important to have...... an engineer experienced in microcontroller programming write the software algorithms to achieve optimal performance. Two mixed signal controller designs based on the same 8-bit microcontroller are compared both theoretically and experimentally. A 16-bit PID compensator with a sampling frequency of 200 k......Hz implemented in the 16 MIPS, 8-bit ATTiny26 microcontroller is demonstrated....

Loss Modelling and Experimental Verification of A 98.8% Efficiency Bidirectional Isolated DC-DC Converter

Directory of Open Access Journals (Sweden)

Ramachandran Rakesh

2017-01-01

In this paper, design and implementation of an ultra-high efficiency isolated bi-directional dc-dc converter utilizing GaN devices is presented. Loss modelling of the GaN converter is also included in this paper. The converter has achieved a maximum measured efficiency of 98.8% in both directions of power flow, using the same power components. Hardware prototype of the converter along with the measured efficiency curve is also presented in this paper.

THE EVOLUTION OF DUSTY STAR FORMATION IN GALAXY CLUSTERS TO z = 1: SPITZER INFRARED OBSERVATIONS OF THE FIRST RED-SEQUENCE CLUSTER SURVEY

Energy Technology Data Exchange (ETDEWEB)

Webb, T. M. A.; O' Donnell, D.; Coppin, Kristen; Faloon, Ashley; Geach, James E.; Noble, Allison [McGill University, 3600 rue University, Montreal, QC, H3A 2T8 (Canada); Yee, H. K. C. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George St., Toronto, ON, M5S 3H4 (Canada); Gilbank, David [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Ellingson, Erica [Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder, Boulder, CO 80309 (United States); Gladders, Mike [Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 (United States); Muzzin, Adam [Leiden Observatory, University of Leiden, Niels Bohrweg 2, NL-2333 CA, Leiden (Netherlands); Wilson, Gillian [Department of Physics and Astronomy, University of California at Riverside, 900 University Avenue, Riverside, CA 92521 (United States); Yan, Renbin [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States)

2013-10-01

We present the results of an infrared (IR) study of high-redshift galaxy clusters with the MIPS camera on board the Spitzer Space Telescope. We have assembled a sample of 42 clusters from the Red-Sequence Cluster Survey-1 over the redshift range 0.3 < z < 1.0 and spanning an approximate range in mass of 10{sup 14-15} M {sub ☉}. We statistically measure the number of IR-luminous galaxies in clusters above a fixed inferred IR luminosity of 2 × 10{sup 11} M {sub ☉}, assuming a star forming galaxy template, per unit cluster mass and find it increases to higher redshift. Fitting a simple power-law we measure evolution of (1 + z){sup 5.1±1.9} over the range 0.3 < z < 1.0. These results are tied to the adoption of a single star forming galaxy template; the presence of active galactic nuclei, and an evolution in their relative contribution to the mid-IR galaxy emission, will alter the overall number counts per cluster and their rate of evolution. Under the star formation assumption we infer the approximate total star formation rate per unit cluster mass (ΣSFR/M {sub cluster}). The evolution is similar, with ΣSFR/M {sub cluster} ∼ (1 + z){sup 5.4±1.9}. We show that this can be accounted for by the evolution of the IR-bright field population over the same redshift range; that is, the evolution can be attributed entirely to the change in the in-falling field galaxy population. We show that the ΣSFR/M {sub cluster} (binned over all redshift) decreases with increasing cluster mass with a slope (ΣSFR/M{sub cluster}∼M{sub cluster}{sup -1.5±0.4}) consistent with the dependence of the stellar-to-total mass per unit cluster mass seen locally. The inferred star formation seen here could produce ∼5%-10% of the total stellar mass in massive clusters at z = 0, but we cannot constrain the descendant population, nor how rapidly the star-formation must shut-down once the galaxies have entered the cluster environment. Finally, we show a clear decrease in the number of IR

Impact of Faults and Protection Methods on DC Microgrids Operation

DEFF Research Database (Denmark)

Bayati, Navid; Hajizadeh, Amin; N. Soltani, Mohsen

2018-01-01

with the DC Microgrid. This paper evaluates and presents a comprehensive review on the most recent studies in the DC Microgrids protection. Moreover, the fault behavior and characteristics of DC Microgrids, the effect of Constant Power Load (CPL) , and recent DC Microgrid protection methods are reviewed. Also...

Blind signal processing algorithms under DC biased Gaussian noise

Science.gov (United States)

Kim, Namyong; Byun, Hyung-Gi; Lim, Jeong-Ok

2013-05-01

Distortions caused by the DC-biased laser input can be modeled as DC biased Gaussian noise and removing DC bias is important in the demodulation process of the electrical signal in most optical communications. In this paper, a new performance criterion and a related algorithm for unsupervised equalization are proposed for communication systems in the environment of channel distortions and DC biased Gaussian noise. The proposed criterion utilizes the Euclidean distance between the Dirac-delta function located at zero on the error axis and a probability density function of biased constant modulus errors, where constant modulus error is defined by the difference between the system out and a constant modulus calculated from the transmitted symbol points. From the results obtained from the simulation under channel models with fading and DC bias noise abruptly added to background Gaussian noise, the proposed algorithm converges rapidly even after the interruption of DC bias proving that the proposed criterion can be effectively applied to optical communication systems corrupted by channel distortions and DC bias noise.

Bifurcation diagram features of a dc-dc converter under current-mode control

International Nuclear Information System (INIS)

Ruzbehani, Mohsen; Zhou Luowei; Wang Mingyu

2006-01-01

A common tool for analysis of the systems dynamics when the system has chaotic behaviour is the bifurcation diagram. In this paper, the bifurcation diagram of an ideal model of a dc-dc converter under current-mode control is analysed. Algebraic relations that give the critical points locations and describe the pattern of the bifurcation diagram are derived. It is shown that these simple algebraic and geometrical relations are responsible for the complex pattern of the bifurcation diagrams in such circuits. More explanation about the previously observed properties and introduction of some new ones are exposited. In addition, a new three-dimensional bifurcation diagram that can give better imagination of the parameters role is introduced

Electrothermal model of choking-coils for the analysis of dc-dc converters

Energy Technology Data Exchange (ETDEWEB)

Gorecki, Krzysztof, E-mail: gorecki@am.gdynia.pl [Gdynia Maritime University, Department of Marine Electronics, Morska 83, Gdynia (Poland); Detka, Kalina [Pomeranian Higher School in Gdynia, Opata Hackiego 8-10, Gdynia (Poland)

2012-09-01

The paper concerns modelling the choking-coil for the needs of the electrothermal analysis of dc-dc converters. A new electrothermal model of the choking-coil is proposed. This model is dedicated for SPICE software and it takes into account nonlinearity of the dependences of the inductance on the current, selfheating and mutual thermal interactions between the core and the winding. The structure of this model is described in detail and its correctness is experimentally verified for the choking-coils with the ferrite and powder cores. Both the characteristics of the choking-coils and the buck converter with these choking-coils were considered. The satisfying agreement between the results of calculations and measurements is obtained.

A VHF Class E DC-DC Converter with Self-Oscillating Gate Driver

DEFF Research Database (Denmark)

Andersen, Toke Meyer; Christensen, Søren K.; Knott, Arnold

2011-01-01

, is inherently resonant, and switching losses are greatly reduced by ensuring Zero Voltage Switching (ZVS) of the power semiconductor devices. A design method to ensure ZVS operation when combining the inverter, rectifier, and gate driver is provided. Several parasitic effects and their influence on converter......This paper describes the analysis and design of a DC-DC converter topology which is operational at frequencies in the Very High Frequency (VHF) band ranging from 30 MHz − 300 MHz. The presented topology, which consists of a class E inverter, class E rectifier, and self-oscillating gate driver...... operation are discussed, and measurement results of a 100 MHz prototype converter are presented and evaluated. The designed prototype converter verifies the described topology....

THE MASSIVE AND DISTANT CLUSTERS OF WISE SURVEY. II. INITIAL SPECTROSCOPIC CONFIRMATION OF z ∼ 1 GALAXY CLUSTERS SELECTED FROM 10,000 deg2

International Nuclear Information System (INIS)

Stanford, S. A.; Gonzalez, Anthony H.; Gettings, Daniel P.; Brodwin, Mark; Eisenhardt, Peter R. M.; Stern, Daniel; Wylezalek, Dominika

2014-01-01

We present optical and infrared imaging and optical spectroscopy of galaxy clusters which were identified as part of an all-sky search for high-redshift galaxy clusters, the Massive and Distant Clusters of WISE Survey (MaDCoWS). The initial phase of MaDCoWS combined infrared data from the all-sky data release of the Wide-field Infrared Survey Explorer (WISE) with optical data from the Sloan Digital Sky Survey to select probable z ∼ 1 clusters of galaxies over an area of 10,000 deg 2 . Our spectroscopy confirms 19 new clusters at 0.7 < z < 1.3, half of which are at z > 1, demonstrating the viability of using WISE to identify high-redshift galaxy clusters. The next phase of MaDCoWS will use the greater depth of the AllWISE data release to identify even higher redshift cluster candidates

Modeling the formation of globular cluster systems in the Virgo cluster

International Nuclear Information System (INIS)

Li, Hui; Gnedin, Oleg Y.

2014-01-01

The mass distribution and chemical composition of globular cluster (GC) systems preserve fossil record of the early stages of galaxy formation. The observed distribution of GC colors within massive early-type galaxies in the ACS Virgo Cluster Survey (ACSVCS) reveals a multi-modal shape, which likely corresponds to a multi-modal metallicity distribution. We present a simple model for the formation and disruption of GCs that aims to match the ACSVCS data. This model tests the hypothesis that GCs are formed during major mergers of gas-rich galaxies and inherit the metallicity of their hosts. To trace merger events, we use halo merger trees extracted from a large cosmological N-body simulation. We select 20 halos in the mass range of 2 × 10 12 to 7 × 10 13 M ☉ and match them to 19 Virgo galaxies with K-band luminosity between 3 × 10 10 and 3 × 10 11 L ☉ . To set the [Fe/H] abundances, we use an empirical galaxy mass-metallicity relation. We find that a minimal merger ratio of 1:3 best matches the observed cluster metallicity distribution. A characteristic bimodal shape appears because metal-rich GCs are produced by late mergers between massive halos, while metal-poor GCs are produced by collective merger activities of less massive hosts at early times. The model outcome is robust to alternative prescriptions for cluster formation rate throughout cosmic time, but a gradual evolution of the mass-metallicity relation with redshift appears to be necessary to match the observed cluster metallicities. We also affirm the age-metallicity relation, predicted by an earlier model, in which metal-rich clusters are systematically several billion younger than their metal-poor counterparts.

ALA-PDT mediated DC vaccine for skin squamous cell carcinoma

Science.gov (United States)

Ji, Jie; Fan, Zhixia; Zhou, Feifan; Wang, Xiaojie; Shi, Lei; Zhang, Haiyan; Wang, Peiru; Yang, Degang; Zhang, Linglin; Wang, Xiuli; Chen, Wei R.

2015-03-01

Dendritic cell (DC) based vaccine has emerged as a promising immunotherapy for cancers. However, most DC vaccines so far have only achieved limited success in cancer treatment. Photodynamic therapy (PDT), an established cancer treatment strategy, can cause immunogenic apoptosis to induce an effective antitumor immune response. In this study, we developed a DC-based cancer vaccine using immunogenic apoptotic tumor cells induced by 5-aminolevulinic acid (ALA) mediated PDT. The maturation of DCs induced by PDT-treated apoptotic cells was evaluated. The anti-tumor immunity of ALA-PDT-DC vaccine was tested with mouse model. We observed the maturations of DCs potentiated by ALA-PDT treated tumor cells, including phenotypic maturation (upregulation of surface expression of MHC-II, DC80, and CD86), and functional maturation (enhanced capability to secret INF-Υ and IL-12). ALA-PDT-DC vaccine mediated by apoptotic cells provided protection against tumor in mice, far stronger than that of DC vaccine obtained from freeze/thaw treated tumor cells. Our results indicate that immunogenic apoptotic tumor cells can be more effective in enhancing DC-based cancer vaccine, which could improve the clinical application of PDT- DC vaccines.

DC KIDS COUNT e-Databook Indicators

Science.gov (United States)

DC Action for Children, 2012

2012-01-01

This report presents indicators that are included in DC Action for Children's 2012 KIDS COUNT e-databook, their definitions and sources and the rationale for their selection. The indicators for DC KIDS COUNT represent a mix of traditional KIDS COUNT indicators of child well-being, such as the number of children living in poverty, and indicators of…

Analysis and Design of a Bidirectional Isolated DC-DC Converter for Fuel Cell and Super-Capacitor Hybrid System

DEFF Research Database (Denmark)

Zhang, Zhe; Ouyang, Ziwei; Thomsen, Ole Cornelius

2012-01-01

Electrical power system in future uninterruptible power supply (UPS) or electrical vehicle (EV) may employ hybrid energy sources, such as fuel cells and super-capacitors. It will be necessary to efficiently draw the energy from these two sources as well as recharge the energy storage elements...... by the DC bus. In this paper, a bidirectional isolated DC-DC converter controlled by phase-shift and duty cycle for the fuel cell hybrid energy system is analyzed and designed. The proposed topology minimizes the number of switches and their associated gate driver components by using two high frequency...

LPV model for PV cell and fractional control of DC/DC converter for photovoltaic systems

OpenAIRE

Martínez González, Rubén; Bolea Monte, Yolanda; Grau Saldes, Antoni; Martínez García, Herminio

2011-01-01

This paper deals with the fractional modelling of a DC-DC converter, suitable in solar-powered electrical generation systems, and the design of a fractional controller for the aforementioned switching converter. A new model for PV cells is proposed in order to obtain a linear equation for V-I characteristic via scheduling dependence of temperature and irradiance. Due to the fractional nature of the ultracapacitors this kind of controller gives a suitable and good performance. Peer Reviewed

LPV model for PV cells and fractional control of DC/DC converter for photovoltaic systems

OpenAIRE

Martínez González, Rubén; Bolea Monte, Yolanda; Grau Saldes, Antoni; Martínez García, Herminio

2011-01-01

This paper deals with the fractional modelling of a DC-DC converter, suitable in solar-powered electrical generation systems, and the design of a fractional controller for the aforementioned switching converter. A new model for PV cells is proposed in order to obtain a linear equation for VI characteristic via scheduling dependence of temperature and irradiance. Due to the fractional nature of the ultracapacitors this kind of controller gives a suitable and good performance. Peer Rev...

GaN-based High Efficiency Bidirectional DC-DC Converter with 10 MHz Switching Frequency

DEFF Research Database (Denmark)

Kruse, Kristian; Zhang, Zhe; Elbo, Mads

2017-01-01

-isolated bidirectional DC-DC converter equipped with Gallium Nitride (GaN) semiconductor transistors is presented. The converter’s operation principles, zero-voltage switching (ZVS) constraints and dead-time effects are studied. Moreover, the optimization and tradeoffs on the adopted high-frequency inductor...... are achieved. Moreover, the measured losses can match the theoretically calculated counterparts well, therefore the design and analysis are verified. However, from the experimental test carried out, it can also be seen, that making a compact converter, even for a GaN-based one, operate at 10 MHz and 100 W...

Zero-Voltage Switching PWM Strategy Based Capacitor Current-Balancing Control for Half-Bridge Three-Level DC/DC Converter

DEFF Research Database (Denmark)

Liu, Dong; Deng, Fujin; Zhang, Qi

2018-01-01

The current imbalance among the two input capacitors is one of the important issues of the half-bridge threelevel (HBTL) DC/DC converter, which would affect system performance and reliability. In this paper, a zero-voltage switching (ZVS) pulse-wide modulation (PWM) strategy including two operation...

Influence of the snubbers and matching transformer on an optimal trajectory controlled resonant transistor DC/DC converter

Directory of Open Access Journals (Sweden)

Bankov Dimitrov Nikolay

2012-01-01

Full Text Available This work examines a series resonant DC/DC optimal trajectory controlled converter during operation above resonant frequency, taking into account the influence of the snubbers and matching transformer. We obtain expressions for the load characteristics, boundary curves between possible modes and limits of the soft commutation area. Computer simulation and experimental observation confirm the theoretical results.

Synthesis and Characterization of Rh-Co Butterfly Clusters Capped by Functionally Substituted 1-Alkynes

Institute of Scientific and Technical Information of China (English)

朱保华; 胡斌; 张伟强; 边治国; 赵全义; 殷元骐; 孙杰

2003-01-01

By the reactions of [Rh2Co2(CO)12] 1 with functionally substituted alkyne ligands HC≡CR 2 (R = FeCp2) and 3 (R = 2-OH-C6H4COOCH2), respectively in n-hexane at room temperature, two new cluster derivatives [Rh2Co2(CO)6(μ-CO)4(μ4, η2-HC≡CR)] 4 (R = FeCp2) and 5 (R = 2-OH-C6H4COOCH2) were obtained respectively. The alkyne was inserted into the Co-Co bond of cluster 1 to give two butterfly clusters. Cluster 4 has been determined by single-crystal X-ray diffraction. Crystallographic data: C22H10Co2FeO10Rh2, Mr = 813.83, orthorhombic, space group P212121, a = 11.5318(7), b = 12.6572(7), c = 17.018(1) A。, V = 2483.9(3) A。3, Z = 4, Dc = 2.176 g/cm3, F(000) = 1568, μ = 3.233 mm-1, the final R = 0.0366 and wR = 0.0899 for 5367 observed reflections with I > 2σ(I). The two clusters have also been characterized by elemental analysis, IR and 1H-NMR spectroscopy.

An Improved Droop Control Method for DC Microgrids Based on Low Bandwidth Communication with DC Bus Voltage Restoration and Enhanced Current Sharing Accuracy

DEFF Research Database (Denmark)

Lu, Xiaonan; Guerrero, Josep M.; Sun, Kai

2014-01-01

Droop control is the basic control method for load current sharing in dc microgrid applications. The conventional dc droop control method is realized by linearly reducing the dc output voltage as the output current increases. This method has two limitations. First, with the consideration of line...... resistance in a droop-controlled dc microgrid, since the output voltage of each converter cannot be exactly the same, the output current sharing accuracy is degraded. Second, the DC bus voltage deviation increases with the load due to the droop action. In this paper, in order to improve the performance......, and the LBC system is only used for changing the values of the dc voltage and current. Hence, a decentralized control scheme is accomplished. The simulation test based on Matlab/Simulink and the experimental validation based on a 2×2.2 kW prototype were implemented to demonstrate the proposed approach....

Fuzzy Controlled Parallel AC-DC Converter for PFC

Directory of Open Access Journals (Sweden)

M Subba Rao

2011-01-01

Full Text Available Paralleling of converter modules is a well-known technique that is often used in medium-power applications to achieve the desired output power by using smaller size of high frequency transformers and inductors. In this paper, a parallel-connected single-phase PFC topology using flyback and forward converters is proposed to improve the output voltage regulation with simultaneous input power factor correction (PFC and control. The goal of the control is to stabilize the output voltage of the converter against the load variations. The paper presents the derivation of fuzzy control rules for the dc/dc converter circuit and control algorithm for regulating the dc/dc converter. This paper presents a design example and circuit analysis for 200 W power supply. The proposed approach offers cost effective, compact and efficient AC/DC converter by the use of parallel power processing. MATLAB/SIMULINK is used for implementation and simulation results show the performance improvement.

single-phase dc phase dc-ac boost converter ac boost converter

African Journals Online (AJOL)

User

systems, need to step-up the DC input voltage. increase the ... design also makes for extra parts, greater system and weight, [1-3]. ... proposes a new design for high performance sin ... SYSTEM ANALYSIS. 2. ..... from the simulation study.

Move to Solar-DC at Home Premises

Indian Academy of Sciences (India)

48V DC line as an additional power line at home. Highly power-efficient usage of Solar; Low-power from grid alone converted from AC-DC. Designed to have minimal loss. Battery can be added with higher efficiency (no convertors), if required.

Electronic DC transformer with high power density

NARCIS (Netherlands)

Pavlovský, M.

2006-01-01

This thesis is concerned with the possibilities of increasing the power density of high-power dc-dc converters with galvanic isolation. Three cornerstones for reaching high power densities are identified as: size reduction of passive components, reduction of losses particularly in active components

Quantum cluster algebras and quantum nilpotent algebras

Science.gov (United States)

Goodearl, Kenneth R.; Yakimov, Milen T.

2014-01-01

A major direction in the theory of cluster algebras is to construct (quantum) cluster algebra structures on the (quantized) coordinate rings of various families of varieties arising in Lie theory. We prove that all algebras in a very large axiomatically defined class of noncommutative algebras possess canonical quantum cluster algebra structures. Furthermore, they coincide with the corresponding upper quantum cluster algebras. We also establish analogs of these results for a large class of Poisson nilpotent algebras. Many important families of coordinate rings are subsumed in the class we are covering, which leads to a broad range of applications of the general results to the above-mentioned types of problems. As a consequence, we prove the Berenstein–Zelevinsky conjecture [Berenstein A, Zelevinsky A (2005) Adv Math 195:405–455] for the quantized coordinate rings of double Bruhat cells and construct quantum cluster algebra structures on all quantum unipotent groups, extending the theorem of Geiß et al. [Geiß C, et al. (2013) Selecta Math 19:337–397] for the case of symmetric Kac–Moody groups. Moreover, we prove that the upper cluster algebras of Berenstein et al. [Berenstein A, et al. (2005) Duke Math J 126:1–52] associated with double Bruhat cells coincide with the corresponding cluster algebras. PMID:24982197

A parameter estimation for DC servo motor by using optimization process

International Nuclear Information System (INIS)

Arjoni Amir

2010-01-01

Modeling and simulation parameters of DC servo motor using Matlab Simulink software have been done. The objective to define the DC servo motor parameter estimation is to get DC servo motor parameter values (B, La, Ra, Km, J) which are significant value that can be used for actuation process of control systems. In the analysis of control systems DC the servo motor expressed by transfer function equation to make faster to be analyzed as a component of the actuator. To obtain the data model parameters and initial conditions of the DC servo motors is then carried out the processor modeling and simulation in which the DC servo motor combined with other components. To obtain preliminary data of the DC servo motor parameters as estimated venue, it is obtained from the data factory of the DC servo motor. The initial data parameters of the DC servo motor are applied for the optimization process by using nonlinear least square algorithm and minimize the cost function value so that the DC servo motors parameter values are obtained significantly. The result of the optimization process of the DC servo motor parameter values are B = 0.039881, J= 1.2608e-007, Km = 0.069648, La = 2.3242e-006 and Ra = 1.8837. (author)

Application of digital control techniques for satellite medium power DC-DC converters

Science.gov (United States)

Skup, Konrad R.; Grudzinski, Pawel; Nowosielski, Witold; Orleanski, Piotr; Wawrzaszek, Roman

2010-09-01

The objective of this paper is to present a work concerning a digital control loop system for satellite medium power DC-DC converters that is done in Space Research Centre. The whole control process of a described power converter bases on a high speed digital signal processing. The paper presents a development of a FPGA digital controller for voltage mode stabilization that was implemented using VHDL. The described controllers are a classical digital PID controller and a bang-bang controller. The used converter for testing is a simple model of 5-20 W, 200 kHz buck power converter. A high resolution digital PWM approach is presented. Additionally a simple and effective solution of filtering of an analog-to-digital converter output is presented.

Dispersed or Clustered Housing for Adults with Intellectual Disability: A Systematic Review

Science.gov (United States)

Mansell, Jim; Beadle-Brown, Julie

2009-01-01

Background: The purpose of this review was to evaluate the available research on the quality and costs of dispersed community-based housing when compared with clustered housing. Methods: Searches against specified criteria yielded 19 papers based on 10 studies presenting data comparing dispersed housing with some kind of clustered housing (village…

Desain dan Implementasi Konverter DC-DC Rasio Tinggi Berbasis Pensaklaran Kapasitor dan Induktor Terkopel untuk Aplikasi pada Photovoltaic

Directory of Open Access Journals (Sweden)

Gusti Rinaldi Zulkarnain

2017-01-01

Full Text Available Seiring dengan berkembangnya pembangkit listrik yang menggunakan photovoltaic sebagai salah satu energi terbarukan, maka berdampak kepada perkembangan teknologi konverter. Tegangan output dari photovoltaic masih perlu ditingkatkan agar mampu dihubungkan pada sistem grid. Salah satu pengembangan topologi konverter boost untuk aplikasi keluaran photovoltaic yaitu konverter DC-DC rasio tinggi berbasis pensaklaran kapasitor dan induktor terkopel. Konverter ini merupakan pengembangan dari konverter gabungan boost-flyback yang ditambahkan rangkaian pensaklaran kapasitor. Kelebihan dari konverter ini adalah memiliki rasio konversi dan efisiensi yang tinggi. Konverter ini mampu menjaga tegangan output konstan ketika tegangan inputnya berubah-ubah. Konverter ini sangan cocok diaplikasikan pada sumber energi alternatif yang menghasilkan tegangan DC rendah seperti photovoltaic.

Asteroid clusters similar to asteroid pairs

Science.gov (United States)

Pravec, P.; Fatka, P.; Vokrouhlický, D.; Scheeres, D. J.; Kušnirák, P.; Hornoch, K.; Galád, A.; Vraštil, J.; Pray, D. P.; Krugly, Yu. N.; Gaftonyuk, N. M.; Inasaridze, R. Ya.; Ayvazian, V. R.; Kvaratskhelia, O. I.; Zhuzhunadze, V. T.; Husárik, M.; Cooney, W. R.; Gross, J.; Terrell, D.; Világi, J.; Kornoš, L.; Gajdoš, Š.; Burkhonov, O.; Ehgamberdiev, Sh. A.; Donchev, Z.; Borisov, G.; Bonev, T.; Rumyantsev, V. V.; Molotov, I. E.

2018-04-01

We studied the membership, size ratio and rotational properties of 13 asteroid clusters consisting of between 3 and 19 known members that are on similar heliocentric orbits. By backward integrations of their orbits, we confirmed their cluster membership and estimated times elapsed since separation of the secondaries (the smaller cluster members) from the primary (i.e., cluster age) that are between 105 and a few 106 years. We ran photometric observations for all the cluster primaries and a sample of secondaries and we derived their accurate absolute magnitudes and rotation periods. We found that 11 of the 13 clusters follow the same trend of primary rotation period vs mass ratio as asteroid pairs that was revealed by Pravec et al. (2010). We generalized the model of the post-fission system for asteroid pairs by Pravec et al. (2010) to a system of N components formed by rotational fission and we found excellent agreement between the data for the 11 asteroid clusters and the prediction from the theory of their formation by rotational fission. The two exceptions are the high-mass ratio (q > 0.7) clusters of (18777) Hobson and (22280) Mandragora for which a different formation mechanism is needed. Two candidate mechanisms for formation of more than one secondary by rotational fission were published: the secondary fission process proposed by Jacobson and Scheeres (2011) and a cratering collision event onto a nearly critically rotating primary proposed by Vokrouhlický et al. (2017). It will have to be revealed from future studies which of the clusters were formed by one or the other process. To that point, we found certain further interesting properties and features of the asteroid clusters that place constraints on the theories of their formation, among them the most intriguing being the possibility of a cascade disruption for some of the clusters.

An immersed field cluster klystron

International Nuclear Information System (INIS)

Palmer, R.B.; Herrmannsfeldt, W.B.; Eppley, K.R.

1989-08-01

Future linear colliders have a need for high power, high frequency, and short-pulse radio frequency sources. The proposed ''cluster klystron'' should give over 1 GW of 12 GHz radio frequency power, can employ direct current or a long high-voltage pulse, but can be gated to give pulses down to a few tens of nanoseconds. The device consists of 42 parallel 100 A channels. Each channel is fed from an individual magnetron-type gun employing a common 50 kV mod-anode. The beams are accelerated to 400 kV in common dc accelerating gaps and fed into the 42 separate klystron channels. Focusing of all channels is achieved by a single overall 4 kG magnetic field. Simulations of expected performance suggest that the efficiency could be above 70%. 10 refs., 6 figs., 5 tabs

Reliability of capacitors for DC-link applications - An overview

DEFF Research Database (Denmark)

Wang, Huai; Blaabjerg, Frede

2013-01-01

DC-link capacitors are an important part in the majority of power electronic converters which contribute to cost, size and failure rate on a considerable scale. From capacitor users' viewpoint, this paper presents a review on the improvement of reliability of DC-link in power electronic converters...... from two aspects: 1) reliability-oriented DC-link design solutions; 2) conditioning monitoring of DC-link capacitors during operation. Failure mechanisms, failure modes and lifetime models of capacitors suitable for the applications are also discussed as a basis to understand the physics......-of-failure. This review serves to provide a clear picture of the state-of-the-art research in this area and to identify the corresponding challenges and future research directions for capacitors and their DC-link applications....

Energetics and dynamics of the neutralization of clustered ions in ammonia and water vapour

International Nuclear Information System (INIS)

Sennhauser, E.S.; Armstrong, D.A.

1978-01-01

The energetics and dynamics of neutralization reactions of clustered ions in ammonia and water vapour have been analysed. Neutralization rate coefficients were calculated for the ions in ammonia and for H + .(H 2 O)sub(n) combining with various clustered anions in water vapour up to densities of 4 x 10 19 molecule cm -3 at 390 K. In the case of ammonia, calculations were also performed at 298 K. For all systems, fractional contributions of the neutralization coefficients for specific cluster sizes to the overall coefficient αsub(eff) were evaluated. The computed value of αsub(eff) for NH 3 was in reasonable agreement with experimental data in the [NH 3 ] range 0.3 to 4 x 10 19 molecule cm -3 , and general trends stemming from the effects of increasing ion mass were pointed out. Calculations of energies of individual cluster sizes indicate possible neutralization reaction mechanisms. With some exception, proton transfer is the only possible path and no H atoms should be formed. This is in general agreement with literature results for water vapour at approximately 390 K and with [H 2 O] >= 2 x 10 x 10 19 molecule cm -3 . (author)