MONTEIRO, A. P.; MONTEIRO, AMANDA P.; PEREIRA MONTEIRO, AMANDA.; http://lattes.cnpq.br/6124700901590921; MONTEIRO, Amanda Pereira.
Resumo:
This work consists of the study, characterization, and analysis of single-phase multi-
level converters based on Cascaded H-Bridge topology. Two groups of configurations
are presented, whose dc-links are formed exclusively by dc-sources or by dc-sources
and a floating capacitor. In this work, these configurations may have two or three
converters in series. In the configuration composed of only dc-sources, there may
be power exchange between the converters, which leads to a bidirectional power
flow for some modulation index values and some dc-link voltage ratios, regardless
of the load power factor. Considering this, switching strategies are presented for
applications where regenerative mode operation is not allowed, forcing all cells
to have a unidirectional power flow and towards the load. In this way, Cascaded
H-Bridge and its various cases of dc-link voltage ratio are discussed and compared
using criteria such as power distribution in each cell, semiconductor power losses,
switching frequency and harmonic distortion. In relation to the Cascaded H-Bridge
with capacitors, two methods are presented to regulate the floating capacitor voltage
by employing redundancies or degrees of freedom. Power distribution in the cells
with capacitive dc-link is analyzed according to the voltage balancing technique
used and in accordance with the variation of the power factor and modulation index
values. In addition, a capacitor voltage control is developed for a three-stage inverter,
so that smooth control actions are imposed to minimize spikes, ripple and THD at
the output voltage of the system and to ensure voltage regulation of the floating
capacitor. Experimental implementations and computational simulations were used
to verify the presented considerations and to show the feasibility of the systems
presented in this work.