| In the Power Electronics industry, three-phase AC-to-DC converters have, until recently, been either uncontrolled or line-commutated phase-controlled rectifiers. Such converters have the inherent characteristic of a decreasing power factor when the firing angles are increased. Another drawback is a high harmonic distortion of the input currents.; Today, low current distortion and unity power factor at the input have become the most important design criteria for AC-to-DC rectification. For a conventional three-phase bridge rectifier feeding a capacitive filter, these two characteristics provide maximum throughput power with negligible ill effects.; In order to obtain low-distortion input current at unity power factor, this thesis will utilize Pulse-Width Modulation (PWM) techniques to implement what is generally known as Active Power Factor Correction, or PFC, on a three-phase boost rectifier.; Although the selection of the power components for the boost rectifier will be addressed, the main focus of this thesis will be the analysis and implementation of a control circuit that will provide the necessary functions for active PFC. The goal is to achieve sinusoidal input currents on all three phases that have low harmonic distortion, and are in phase with their respective line voltages. |
