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Comparison of 2- and 3-level Active Filters with Enhanced Bridge-Leg Loss Distribution
Thiago B. Soeiro,Mario Schweizer,Jorgen Linner,Per Ranstad,Johann W. Kolar 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
In this paper an efficiency comparison between 3-phase shunt active filters derived from the 2-level VSC, the 3-level NPC, Active NPC (A-NPC) and the T-type VSC is presented. In order to address the loss distribution issue of the 3-level topologies, while keeping the efficiency of the system high, a space vector modulation scheme incorporating a special clamping of the phase is proposed. It is shown that 3-level active filters can have their losses well distributed over the chip dies, leading to only a small difference in their operating temperatures. Additionally, a semiconductor area based comparison is used to further evaluate the studied active filter systems. Finally, experimental results obtained with a 12kVAr/48㎑ 3-level NPC based shunt active filter employing custom SiC power modules are presented in order to demonstrate the performance and feasibility of this solution.
Comparison of Electrostatic Precipitator Power Supplies with Low Effects on the Mains
Thiago B. Soeiro,Thomas Friedli,Jorgen Linner,Per Ranstad,Johann W. Kolar 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
In this article, the distortions caused by the power supplies employed in Electrostatic Precipitators (ESP) are investigated, and means for improving the line power quality are proposed. Multi-pulse and PWM rectifier topologies and other concepts including hybrid systems and active filters are evaluated in order to identify suitable systems for ESP applications. A comparison of the studied systems rated to 60 ㎾ and fully designed employing commercial components is shown. The ESP systems efficiency, power density, current harmonic THD, among others features are used for the assessment. The loss calculations are extended to a variable chip area to allow a fair comparison between the studied systems. Finally, the VIENNA 6-switches rectifier and active filter concepts are chosen and experimental analyses are carried out, verifying the performance and feasibility of the proposed systems.
Evaluation of bioenergetic and mitochondrial function in liver transplantation
Rui Miguel Martins,João Soeiro Teodoro,Emanuel Furtado,Anabela Pinto Rolo,Carlos Marques Palmeira,José Guilherme Tralhão 대한간학회 2019 Clinical and Molecular Hepatology(대한간학회지) Vol.25 No.2
Background/Aims: We measured changes in mitochondrial function and bioenergetics that occur during ischemia/ reperfusion in fresh liver samples of patients undergoing liver transplantation. These variations correlated with markers of liver function and clinical outcome. Ischemia/reperfusion injury related to liver transplantation affects mitochondrial function and bioenergetics. Experimental studies were conducted to identify the role of bioenergetics and mitochondrial dysfunction. To the best of our knowledge, no investigation of these two factors’ impacts on liver transplantation has been performed. Methods: This was a prospective study of 28 patients who underwent liver transplantation. We measured parameters of mitochondrial function and bioenergetics in biopsies performed during the procedure. Results: We observed a statistically significant reduction in mitochondrial membrane potential, an increase in lag phase, and decreases in mitochondrial respiration and adenosine triphosphate content (P<0.010). Higher postoperative aminotransferase peaks correlated with worse mitochondrial function; mitochondrial respiration correlated with arterial lactate (P<0.010). Conclusions: There is a relationship between mitochondrial function and ischemia/reperfusion injury. The future use of these clinical markers as prognostic factors may allow early identification of post-transplant liver failure and may indicate the need to perform a new transplant.
Aditya Shekhar,Thiago Batista Soeiro,Laura Ramirez-Elizondo,Pavol Bauer 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
During the operation of a three line ac link in parallel with a ac-dc-ac link system that employs Back-to-Back (B2B) Medium Voltage Modular Multilevel Converters (MMC), a path for the low frequency zero sequence currents is shown to exist. Apart from causing additional losses, these currents can result in limitations on power capacity. A detailed analysis on the influence of cell capacitance, arm inductance and link conductor length on the circulating zero sequence currents and the means to mitigate them through a simulated control strategy is investigated. The simulations show that the dc link employing B2B-MMC can successfully operate in parallel with ac link without transformer isolation by controlling the zero sequence currents.
Aditya Shekhar,Lucia Beloqui Larumbe,Thiago Batista Soeiro,Yang Wu,Pavol Bauer 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
There is an increasing focus on integrating flexible dc links for bulk power routing in medium voltage distribu-tion grids. In such applications, the ac-dc Modular Multilevel Converter (MMC) devised for medium voltage and high-power ratings can be an interesting choice. This paper highlights some less explored design trade-offs arising due to the limitation on N in relation to modulation frequency and arm inductance. Specifically, the study intends to describe the interdependent influence of each degree of freedom on several aspects such as capacitor voltage balancing, circulating currents and harmonic performance. Finally, the importance of considering interhar-monics in the performance assessment of the MMC instead of the conventional interpretation of distortion calculation is highlighted.
Application of 1.7-kV 700-A SiC LinPak to Optimize LCL Grid-Tied Converters
Ki-Bum Park,Ralph M. Burkart,Bruno Agostini,Thiago B. Soeiro 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
The current rating of SiC MOSFETs has been increased ever since its introduction. Yet, high current modules for 690-V and beyond grid applications, which would enable the realization of megawatt range converters, are not readily commercially available. Recently, a new high current 1.7-kV SiC MOSFET module suitable for hardparallel connection to increase the current rating has been introduced. This paper investigates the system-level benefit of this module for a 2-level 690-V 1-MW grid-tied converter regarding achievable efficiency and power density and benchmarks the results against the achievable performance with conventional Si IGBTs. The study analyzes in detail the impact of the number of paralleled modules, the choice of the cooling system and the filter design.
In vitro and in vivo experimental models for drug screening and development for Chagas disease.
Romanha, Alvaro José,Castro, Solange Lisboa de,Soeiro, Maria de Nazaré,Correia,Lannes-Vieira, Joseli,Ribeiro, Isabela,Talvani, André,Bourdin, Bernadette,Blum, Bethania,Olivieri, Bian O Instituto 2010 Memórias do Instituto Oswaldo Cruz Vol.105 No.2
<P>Chagas disease, a neglected illness, affects nearly 12-14 million people in endemic areas of Latin America. Although the occurrence of acute cases sharply has declined due to Southern Cone Initiative efforts to control vector transmission, there still remain serious challenges, including the maintenance of sustainable public policies for Chagas disease control and the urgent need for better drugs to treat chagasic patients. Since the introduction of benznidazole and nifurtimox approximately 40 years ago, many natural and synthetic compounds have been assayed against Trypanosoma cruzi, yet only a few compounds have advanced to clinical trials. This reflects, at least in part, the lack of consensus regarding appropriate in vitro and in vivo screening protocols as well as the lack of biomarkers for treating parasitaemia. The development of more effective drugs requires (i) the identification and validation of parasite targets, (ii) compounds to be screened against the targets or the whole parasite and (iii) a panel of minimum standardised procedures to advance leading compounds to clinical trials. This third aim was the topic of the workshop entitled Experimental Models in Drug Screening and Development for Chagas Disease, held in Rio de Janeiro, Brazil, on the 25th and 26th of November 2008 by the Fiocruz Program for Research and Technological Development on Chagas Disease and Drugs for Neglected Diseases Initiative. During the meeting, the minimum steps, requirements and decision gates for the determination of the efficacy of novel drugs for T. cruzi control were evaluated by interdisciplinary experts and an in vitro and in vivo flowchart was designed to serve as a general and standardised protocol for screening potential drugs for the treatment of Chagas disease.</P>
L. Schrittwieser,M. F. Vancu,J. W. Kolar,T. B. Soeiro 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
This paper introduces a phase-oriented control strategy for the uni- and bidirectional three-phase, bucktype SWISS Rectifier. It allows phase shifted sinusoidal input currents which enable the generation of capacitive or inductive reactive power at the converter’s AC grid interface. Furthermore, the operation of the SWISS Rectifier with unsymmetrical AC mains voltages is analyzed. Modifications of the control structure, allowing constant AC input power or ohmic mains behavior even with unsymmetrical AC voltages are presented. Simulations and measurements taken on a 7:5 kW bidirectional SWISS Rectifier hardware prototype demonstrate the validity of the theoretical considerations.