Estudo, controle e implementação do conversor Boost PFC operando no modo de condução mista

Abstract

This Master Thesis presents the study and proposes a digital control system applied to the PFC boost converter operating in mixed conduction mode. The motivation to this subject, a bibliographic review of the existing current control techniques and the objectives of this work are presented in the first chapter. The control system is composed of a current loop, which has the objectives to provide low harmonic content to the input current and high power factor to the converter, and a voltage loop, which has the goal to regulate the output voltage of the converter. Initially, the study of the conduction modes of the PFC boost converter, highlighting their operation conditions, and details of the mixed conduction mode operation are showed. Next, two predictive digital current controllers with feedforward action are approached in details, including the equations deduction, block diagram, operation process, design, simulation results and parametric variation analysis. A comparative analysis between both controllers is also accomplished. The proportional-integral voltage controller is presented following, comprising its structure, design and simulation results. After, issues related to the practical implementation of the converter and control system, as the converter design and the control device programming, are shown. Finally, the experimental results obtained through the implementation of the proposed system, including the waveforms acquired using a prototype constructed in laboratory and the quality indexes as the power factor and the total harmonic distortion, are presented with the purpose to validate and prove the content of this work.