A New Flexible and Compact High-Frequency Link On-Line UPS System

Abstract

This paper introduces a new high-frequency (HF) link on-line Uninterruptible Power Supply (UPS) configuration based on one HF transformer with three windings. The HF link is established using a resonant inverter during normal operation of the UPS and a sinusoidal pulse-width modulation (SPWM) inverter during mains failure. A cycloconverter is used to construct the low-frequency output voltage. Another configuration of the system is also presented such that the system becomes more compact and flexible where the switch-mode operation of the SPWM inverter is avoided by replacing it with a resonant one. In this case, the two inverters are integrated into only one HF resonant inverter and the output is constructed and controlled using a SPWM cycloconverter. The choice of the switching frequency as well as the HF transformer material are investigated. Simulation of the UPS circuit was carried out and verified with experimental results for a 500 VA, 20kHz link frequency.

Key Words:

• UPS
• PWM converters
• resonant inverters
• HF transformers

Additional information

Notes on contributors

T. H. Abdelhamid

Ing. Tamer Abdelhamid was born in Alexandria, Egypt 1962. He received the B.Sc. and M.Sc. in Electrical Engineering from Alexandria University in 1984 and 1989 respectively. Since 1984, he has been with the Department of Electrical Engineering of Alexandria University, Egypt. At present, he is a Ph.D. student in the Electrical Engineering Department at Brunel University, London, UK. His research interests include static power converters with a special emphasis on soft switching.

M. K. Darwish

Dr. M. K. Darwish was born in Alexandria, Egypt 1955. He received the B.Sc. degree in electrical engineering from Helwan University, Cairo, Egypt, and the Ph.D. degree from Brunel University, England, in 1978 and 1987 respectively. From 1983 to 1987 he was an SERC supported Research Assistant at Brunel University, where he worked on pioneering work on switched-capacitor filters. After obtaining his Ph.D. degree he joined the Department of Electrical Engineering at Brunel University as a Lecturer in Power Electronics. His research interests include active filtering techniques. UPS systems and high-frequency converters.

P. Mehta

Dr. P. Mehta received the B.Sc. degree in electrical engineering from St. Andrews University, England, in 1966 and the Ph.D. degree from Bristol University, Bristol, England, in 1970. Following a short training period with Uganda Electricity Board, East Africa, he joined a Rey-rolle & Co, Ltd., England as a Research Engineer. He then joined Westinghouse Brake & Signal, England as a Design Engineer working on thyristor converters. He is presently a Reader in Power Electronics at Brunel University, England. His research interests include intelligent buildings, active filters and high-frequecy techniques.