Универсальный подход к исследованию AC/DC-преобразователей повышающего типа

Abstract

Three-phase AC/DC boost converters performing power factor correction are widely used at present. They ensure electromagnetic compatibility of the converter with the network and decrease the network load by making the phase currents proportional and co-phase with the phase voltages. Typically, a three-phase AC/DC boost converter contains input power reactors and a three-phase bridge rectifier. Better power factor value is achieved in such devices by applying three choppers based on bidirectional power switches or power transistor legs. However, a large number of controllable devices and components, the current states of which depend on their pre-switching state, is a factor that adds much difficulty to studying the electrical processes in the converter. A principle of reducing the number of equivalent circuits necessary for studying the electrical processes in the converters under consideration is described. The proposed principle follows from assumptions based on the target operating mode of an AC/DC boost converter. Three converters have been investigated by applying this principle of reducing the number of equivalent circuits with using the electric circuit theory (Kirchhoffs equations or the mesh-current method) techniques. Examples of applying the proposed approach for studying three-phase AC/DC boost converters (so-called Vienna rectifiers) are given. The proposed approach made it possible to decrease the number of analyzed equivalent circuits down to eight ones, and the conclusions drawn from an analysis of the obtained equivalent circuits were used to select the best configuration of a three-phase AC/DC boost converter. The obtained results are of interest for developers of three-phase power factor correction converters, uninterruptible power sources, frequency converters, and other AC/DC converters complying with more stringent requirements for the power factor, efficiency, and device prime cost.