169,913 research outputs found
Analysis on multilevel inverter powertrains for E-transportation
No full textThe existing electric vehicles uses conventional 2-level inverters with high frequency modulation. But, they manifest some issues like high dv/dt, high torque ripple and high blocking voltage, leading to performance deterioration. Multilevel inverters address these issues and yield quasi sinusoidal output waveform, thus they represent a valuable solution to above issues, but at the cost of increased complexity, cost, and potential failure rate, due to the increased component count. Therefore, while developing multilevel converters for powertrains, the optimal number of levels has to be determined which affects overall performance and cost. Hence, accurate trade-offs among various parameters which are critical for the wide acceptance of the technology are a prerequisite. Therefore, this article is dedicated towards an evaluation of the effects of the number of levels in multilevel converters for e-powertrains and recommends a unique choice to enhance vehicle performance over conventional 2-level inverters. To validate the simulation results, a prototype of powertrain is implemented and the output is fed to a 3-phase permanent magnet synchronous machine. It is also concluded that use of multilevel inverter is worthwhile compared to the conventional 2-level inverter for electrification of the car fleet
Seven-level cascaded inverters for Uninterruptible Power Supply (UPS) applications
No full textThis paper considers single phase seven-level cascaded H-bridge (CHB) inverters for Uninterruptible Power Supplies (UPS) applications and proposes a fundamental switching frequency procedure, based on graphic analysis, to improve the output waveform quality. It fixes the first switching angle and gets the other two by intersection of harmonics functions set to zero. The performances of the proposed procedure, in terms of total harmonic distortion (THD), are compared with those obtained by a procedure that identifies the two remain optimal switching angles through a THD minimization algorithm. Experimental results are obtained by measurements performed on a prototype built at DigiPower laboratory. The agreement between computed and experimental results confirms the accuracy of the presented procedure
Alpha-interferon therapy in chronic hepatitis C: prediction of response by virus and host related factors.
No full textNOVEL INHIBITORS OF PVHL-ELONGIN C BINDING
No full textThe present invention relates to novel inhibitors of pVHL-Elongin C binding, methods for identifying such inhibitors as well as compounds comprising a first moiety binding to an Elongin B, Elongin C, Cul2 and/or Rbx1 complex, a linker and a second moiety for HIF-2α
Primary effusion lynphoma cells undergoing human Herpesvirus type 8 (HHV8) productive infection produce C-type retroviral particles.
No full textPrimary effusion lymphomas (PELs) are invariably infected by the human herpesvirus 8 (HHV8)that is present in most PEL cells as latent virus but replicates in a subset of permissive cells to produce infectious progeny. Here we show that productively infected PEL cells release C-type retrovirus-like particles encoding an Mn++-dependent RT activity, which is typical of endogenous retroviruses. Strikingly, C-type particles are produced only in cells showing advanced HHV8 morphogenesis. Phorbol esters, which induce productive HHV8 replication and morphogenesis in PEL cells, increase RLP production. Phosphonoacetic acid, a blocker of HHV8 late gene expression, inhibits the production of C-type particles, whereas neutralizing anti-alphaIFN antibodies, which are known to increase HHV8 assembly, increases C-type particle production. These data suggest that factors expressed in advanced stages of HHV8 reactivation support endogenous C-type particle morphogenesis in PEL cells
A high efficiency Selective Harmonic Elimination technique for multilevel converters
No full textThis paper proposes a selective harmonic elimination (SHE) technique capable to remove all harmonics except those having order n = 4sk +/- 1, k = 1, 2, 3,... from the output voltage of a l-level inverter, l = 2s + 1, where s is the number of the dc sources. It is shown that a very low total harmonic distortion (THD) factor is obtained. The proposed technique produces fundamental frequency pulses, therefore high efficiency is ensured. Experimental results, obtained for an 9-level inverter, confirm the validity of the proposed modulation
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Mixed harmonic elimination and reduction technique for single phase nine level converters
No full textThis paper presents a procedure that works at fundamental frequency to compute switching angles in single phase 9-level converters to eliminate the third and odd triple harmonics and to reduce other low order harmonics, obtaining a low total harmonic distortion (THD). The DC voltages feeding the converter, that are equal, but variable, allow to obtain switching angles independent on modulation index. The proposed procedure consists in a minimization of THD by means of a suitable graphical procedure. It's mathematically demonstrated that the third and all odd multiple of the third harmonic are deleted. Simulation results, obtained by using Matlab/Simulink, are shown
Investigation about SHM-PAM procedure for grid connected CHB seven level inverters
No full textThis paper considers single phase cascaded H-bridges seven level inverters and proposes a pulse amplitude modulation procedure operating at fundamental frequency that mitigates many harmonics from its output voltage waveform, allowing to obtain low total harmonic distortion. The procedure fixes three switching angles and defines the values of the dc source voltages depending on them. Switching angles and total harmonic distortion are constant with modulation index m that can be changed by varying dc voltage sources that depend linearly on m. An investigation about results obtained by different switching angles choices is presented. Comparisons between simulated and experimental results are shown in order to highlight the accuracy of the proposed procedure
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