No Blog Eletrônica de Potência você encontrará informações sobre teses,artigos,seminarios,congressos,tecnologias,cursos,sobre eletrônica potência.
“TEMOS O DESTINO QUE MERECEMOS.
O NOSSO DESTINO ESTA DE
ACORDO COM OS NOSSOS MERITOS”
ALBERT EINSTEIN.
Imagination is more important than knowledge, for knowledge is limited while imagination embraces the entire world.
EL FUTURO SE CONSTRUYE HOY,EL SUCESSO NO ES FRUTO DE LA CASUALIDAD,SE HUMILDE ,APRENDE SIEMPRE CADA DIA.
AUTOR DO BLOG ENG.ARMANDO CAVERO MIRANDA SÃO PAULO BRASIL
"OBRIGADO DEUS PELA VIDA,PELA MINHA FAMILIA,PELO TRABALHO,PELO PÃO DE CADA DIA,PROTEGENOS DO MAL"
“SE SEUS PROJETOS FOREM PARA UM ANO,SEMEIE O GRÂO.SE FOREM PARA DEZ ANOS,PLANTE UMA ÁRVORE.SE FOREM PARA CEM ANOS,EDUQUE O POVO.”
“Sixty years ago I knew everything; now I know nothing; education is a progressive discovery of our own ignorance.
Will Durant”
Abstract)
This paper presents a novel cascaded multilevel PWM ac-ac converter that can solve commutation problem.
By cascading the single-phase PWM ac-ac converter that uses basic switching cell structure and coupled
inductors, the proposed converter does not need to sense the voltage or current polarity for safe commutation.
When many unit-cells are cascaded, the proposed converter has more output voltage levels and can obtain
high ac output voltage by using low voltage rating switching devices. By applying phase-shifted PWM
technique, the proposed converter can reduce output filter size significantly. A 2 kW prototype converter
having four unit-cell structure is built and tested to verify the performance.
*
INTRODUCTION
1.1 Background
A power distribution system is similar to a vast network of rivers. It is important to
remove any system faults so that the rest of the power distribution service is not
interrupted or damaged. When a fault occurs somewhere in a power distribution system,
the voltage is affected throughout the power system. Among various power quality
problems, the majority of events are associated with either a voltage sag or a voltage
swell, and they often cause serious power interruptions.
A voltage sag condition implies that the voltage on one or more phases drops below
the specified tolerance for a short period of time. A voltage swell condition occurs when
the voltage of one or more phases rises above the specified tolerance for a short period of
time. The causes of voltage sags and swells are associated with faults within the power
distribution system. Users located a close distance to the fault experience voltage sags
much greater in magnitude and duration than users located farther away, and as the
power distribution system have power interruptions during a fault because of the effects
of a voltage sag or voltage swell produced in the system by the fault. The objective of
this research is to develop a novel voltage control scheme that can compensate for
voltage sag and swell conditions in three-phase power systems.
Power Electronics: A New Beginning By Slobodan Ćuk, TESLAco
Power Electronics progress depends on the progress in its two constituent areas: System Technology and Power Management Technology, which had been traditionally developed in the past in companies specializing in either one or the other area of expertise. System Technology companies, or Power Supply companies relied heavily on the use of the components (switches, drive and control circuits) developed by Power Management companies.
The System Technology popularly known as converter topologies has changed very little in last 50 years and is, in fact, the key reason why the Power Electronics as whole has progressed much less despite the tremendous advances made by Power Management companies in developing the new switching devices with ever increasing switching devices power and speed improvements and high performance digital control circuits.
The conventional topologies are analyzed and the sources of their deficiencies are established. This, in turns, leads to the new switching methods and the corresponding novel switching converter topologies which are overcoming all these deficiencies. However, no incremental change will do, but a fresh new look is needed. Hence what is needed is: Power Electronics: A New Beginning!
Dr. Slobodan Ćuk
Dr. Ćuk received his bachelor degree from Belgrade University, Yugoslavia, 1970, MSEE degree from University of Santa Clara, USA 1974 and her Ph.D. from Caltech, California , USA, 1976.
Dr. Ćuk was the full-time Professor of Electrical Engineering at the California Institute of Technology until January 1, 2000 where he conducted research and taught courses in Power Electronics and Fundamentals of Energy Processing. During his 25 years at Caltech, more than 35 students obtained Ph.D. degree in Power Electronics under his guidance. More than dozen of his former students are Professors of Power Electronics in U.S. and abroad while others are leading researchers in the industry.
For the invention of Integrated Magnetics Dr. Ćuk obtained a 1991 Edward Longstreth Medal from Franklin Institute which was for the first time in its 100 years history awarded to researchers in Power Electronics. His publications include over 100 scientific papers in the Power Electronics field and a three-volume book on Switched-Mode Power Conversion.
Over a span of 20 years, Dr. Ćuk has taught a number of public and in-house courses in United States, Europe and Far East, which were attended by over 4,000 Power Electronics specialists. In 1979, Dr. Ćuk founded TESLAco. He holds over 20 patents in switching power conversion filed. Over dozen patents on Ćuk Optimum Power Conversion technology are pending or are currently in preparation.
Dr. Ćuk’s Inventions and Discoveries
1. Optimum Topology Converter, known as the ĆUKconverter (1974)
2. Coupled-Inductor and Integrated Magnetics method (1975)
3. State-space averaging method (1975)
4. TESLAconverter (2000)
5. Hybrid-switching and Storageless-Switching Method (2009)
6. New DC-DC and Bridgeless AC-DC converter topologies (2010):
A study on Auto Transformer protective method
for AC electric railway system.
Son, Dong-Shic
Department of Railroad Engineering
The Graduate School of Green Railroad
Woosong University
An AC electric railway uses AT(auto transformer), BT(Booster
Transformer), and direct power feeding system. Today, as a result of an
increase in use of load current system, AT feeding system has became a
mostly and widely used system due to its profitability in high and
long-distance power feeding and inductive interference.
AT is a core facility of the AC electric railway, a major public
transportation, in AT traction power feeding system thus, the suspension of
train operation due to the malfunction of AT feeding system would causes
not only a high volume of civil petitions but also an interruption to the
power supply to the train that could bring a second incident.
In general, the power transformer protection is classified into electronic
protection that includes differential protection (87T), over current protection
(50/51), and earth fault protection (50/51N), and the mechanical protection
such as buchholz relay, sudden pressure relay, winding temperature indicator,
temperature indicator for insulation oil however, the failure in the operation of
AT is protected only by an alarm signal controlled by substation using
current and impedance relay. Therefore, to prevent the failure in mechanical
protection, sectioning post(SP), sub-sectioning post(SSP), and parallel post(PP)
needs to be protected by electronic protection as well as mechanical
protection. In addition, accidents related to AT traction power supply system
are divided into an outside (on railroad) accident mostly occurred due to
traction line earth(T-R earth), feeding line earth(F-R earth), sectioning line
earth(F-R earth), and short circuit(T-R short circuit) between feeding and
sectioning linen, and an inside (at substation) accident mostly occurred due to
earth and short circuit of AT winding furthermore, no matter what type of
accident related to AT traction power supply system occurs it is protected by
over current or impedance relay from substation Even though the AT
related accidents could result in the discontinuation of rail service due to an
inability to separate the feeder section, it is difficult to find whether the type
of accident is outside or inside. As a result, it unnecessarily costs long time
to deal with the accident because of unclearness of the cause.
