Estudo de retificadores multiníveis com células em cascata

Abstract

The growing demand for electrical energy and the need for compliance with strict power quality standards have driven the development of active rectifiers with high power factor. Multilevel rectifiers present themselves as a superior solution to conventional rectifiers for medium and high-voltage applications, offering lower harmonic distortion and reduced voltage stress on semiconductors. However, the high component count in classic topologies, such as the Cascaded H-Bridge (CHB), increases the system cost and complexity. This work presents the analysis, modulation, and simulation of two single-phase unidirectional multilevel rectifier configurations based on cascaded cells with reduced switch count. This study focuses on the symmetrical and asymmetrical operation of the topologies, utilizing two cells (k = 2) to synthesize from five to nine voltage levels at the input. The symmetrical approach simplifies control and allows for modular standardization, while the asymmetrical approach provides a higher number of voltage levels. The methodology encompasses the mathematical description of the cells’ operation, the development of an adapted level-shifted PWM strategy, and the input current control. The results obtained via computational simulation validate the system performance, demonstrating that the studied configurations ensure sinusoidal input currents with low Total Harmonic Distortion (THD), unity power factor, and effective output voltage regulation, combining high power quality with a simplified structure.