Modern Transformerless Uninterruptable Power Supply (UPS) Systems brahim Güne 1, Bülent Üstüntepe2, and Ahmet M. Hava3 1,2 ENEL Energy Electronics Company, 34794 Istanbul TURKEY

Department of Electrical and Electronics Engineering, Middle East Technical University, Ankara, TURKEY
hava@metu.edu.tr

Abstract
Uninterruptable power supplies (UPS) are widely used to
supply critical loads and provide reliable and high quality
energy to the load. Until recently, on-line UPS systems with
isolation transformer have been widely employed. However,
transformerless modern UPS systems have been rapidly
replacing the old technology due to their superior
performance and size attributes. Transformerless UPS
systems have utility friendly input performance and high
quality output voltage waveform. Furthermore, smaller size,
higher efficiency, and increased reliability are features that
spread the transformerless products, rendering the
transformer technology obsolete. In this paper, modern
transformerless UPS systems with the 6-300kVA range will
be discussed and their experimental performance will be
illustrated. Input and output power quality performances,
energy efficiency performance, and size/weight information
will be provided on modern commercial transformerless
UPS products.
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GLORIOSA PROMOCION XIX INGENIERIA ELECTRONICA UNIVERSIDAD NACIONAL MAYOR DE SAN MARCOS 1985 LIMA PERU

SALUDOS DESDE SAO PAULO A MI ALMA MATER UNIVERSIDAD NACIONAL MAYOR DE SAN MARCOS FACULTAD DE INGENIERIA ELECTRONICA 1985-LIMA -PERU
PADRINO ING. SEIICHI KARIYA

Development of a Power Factor Corrected High Current Supercapacitor Charger for a Surge Resistant UPS Zhang, Xu

Development of a Power Factor Corrected High Current Supercapacitor Charger for a Surge Resistant UPS

Zhang, Xu

Identifier: http://hdl.handle.net/10289/7048

Date: 2012

Type: Thesis

Degree Name: Master of Science (MSc)

Publisher: University of Waikato

Rights: All items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.

Abstract:

The Uninterrupted Power Supplies (UPSs) provide short term power back up to electrical loads when the mains power fail. Usually UPSs employ battery packs as the energy storage device. However the limitations of battery packs can affect the UPS performance.
As an alternative energy storage device, the supercapacitor (SC) technology is well developed over the past 30 years. Due to recent developments, single cell commercial supercapacitors are available up to about 5000 farads. Over the past 10 years, supercapacitor direct current (DC) voltage ratings have gradually increased to about 2.7 V/cell. New lithium based supercapacitor families have DC ratings up to 3.5 V/cell. For the high current applications, the supercapacitors have some advantages over batteries, which are the low effective series resistance (ESR), high power densities and high surge withstand capability.
This thesis is a continuation of the work begun by Kozhiparambil, P. K. on Surge Resistant Uninterrupted Power Supply (SRUPS). The reason for this continual research is due to identify weaknesses in original of SRUPS work with regard to the design of the charger. To reduce the components contain, also achieve common mode transient rejection capability, a flayback mode high current charger with power factor correction has been developed for charging the SC banks.
The prototype circuit includes multiple SC banks to transfer the energy from the 240 V, 50 Hz power line to the load maintaining high isolation level. The loads receive continuous and surge free power from the SC banks, and has electrical isolation from the main power line. An IGBT is used as a switch for the flyback charger, which has the advantage of high current capability.
The experimental results show the design was valid for the SRUPS and it demonstrated the capability to transfer the energy through a flyback charger with power factor correction.

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