Three-Phase Buck/Boost-type High-Power-Factor Switching Converter.

Abstract

The harmonic pollution caused by ac-to-dc converters has been our great concern. To overcome the problem, several Power-Factor-Correction (PFC) converters have been developed and applied in practice in recent years.However, several power converter systems, such as motor drive system with a wide V/F control range, uninterruptible power supply system, and dc power supply system with an universal input voltage range, require an ac-to-dc converter or an off-line converter (pre-regurator) with a wide output-voltage control range to obtain high efficiency. But the most conventional PFC converters employ a Voltage-Fed or Current-Fed type topology and they have lower or upper limitation of the output-voltage control range. Thus, they do not realize sufficiently high system efficiency.On the other hand, a Buck/Boost converter has a wide control range of the output voltage and acts PFC operation under an appropriate control technique. Thus, the study of a possibility about the Buck/Boost ac-to-dc converter with PFC and a wide output-voltage control range is important to realize harmonic-free and efficient power conversion systems.In this paper, the author proposes a three-phase bridge-type ac-to-dc converter system with a high input power factor and a wide output-voltage control range. The controller of the proposed system includes following two new techniques. One is the “Pulse-Space-Modulation” to compensate modulation errors in conventional Pulse-Width-Modulation caused by dc current ripples or fluctuations of the current pulse amplitude. The other is a switching pulse pattern generator, using the idea of equivalent pulse current source for the bridge, to simplify the pulse pattern generation process.In the following, the paper describes the proposed converter system, the control and modulation principles, and experimental results that show the reliability and usefulness of the proposed Buck/Boost converter system. Finally, the paper concludes the contents of this paper.