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A novel three-phase three-port UPS employing a single high-frequency isolation transformer | IEEE Conference Publication | IEEE Xplore

A novel three-phase three-port UPS employing a single high-frequency isolation transformer


Abstract:

A three-phase PWM rectifier and a three-phase PWM inverter are coupled via two four-quadrant full-bridge converter cells and a high-frequency isolation transformer. By em...Show More

Abstract:

A three-phase PWM rectifier and a three-phase PWM inverter are coupled via two four-quadrant full-bridge converter cells and a high-frequency isolation transformer. By employing a third transformer winding and further full-bridge cell battery energy storage is incorporated into the power transfer between rectifier and inverter resulting in a three-port UPS concept. The phase shift control of the power flow between the ports is analyzed for square-wave operation of the full-bridge cells. Furthermore, the utilization of the degrees of freedom of the system control, i.e. the extension to duty cycle control for optimizing the system behavior is discussed and control laws ensuring minimum overall system losses are derived. Finally, a control-oriented converter model is proposed and the decoupled control of the power flow of the ports is treated briefly. All theoretical considerations are verified by simulations using PSIM.
Date of Conference: 20-25 June 2004
Date Added to IEEE Xplore: 15 November 2004
Print ISBN:0-7803-8399-0
Print ISSN: 0275-9306
Conference Location: Aachen, Germany

I Introduction

Highly reliable three-phase on-line uninterrupted power supply systems (UPS) are formed by back-to-back connection, i.e. DC side coupling of a mains-side voltage source rectifier and a load-side voltage source inverter [1]. There, the battery energy storage is directly connected to the DC link or coupled via a DC/DC converter in order to allow a control of the charging or discharging current and a compensation of battery voltage changes. Furthermore, for safety reasons and voltage level adaption in general a 50/60Hz isolation transformer is employed on the input or output side which, however, constitutes a significant drawback concerning volume/weight, costs and efficiency.

References

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