Sistemas de conversão CC-CA e CA-CC monofásicos multiníveis em cascata.

Abstract

The aim of this work is to analyze a family of twelve single-phase multilevel aJld cascade convertera with two power cells in DC-AC (bidirectional power flow) aJld AC-DC (unidirectional) modes. In the case of inverters, fully controllable legs which are capable of generating two and three voltage leveis are used in the two cells. For the rectifiers, these legs comprise only Cell B since reduced and passive legs are used in Cell A, they have a reduced number of switches and give the rectifiers in this work a unidirectional feature. In both cases, the DC-link voltage ratio are asymmetric and the total voltage of the lowest voltage cell is supplied exclusively by the capacitors that compose it, they are called floating capacitors. The modulation technique used is the level-shifed carriers, always prioritizing the switching between the two nearest voltage leveis to minimize harmonic distortion in the generated signals. The algorithms needed to balance the voltages of the four capacitors are presented, as well as the contrai techniques aJld the LS-PWM (Level-Shifted Pulse-Width Modulation) vector sequences. In addition, the results of computational simulations in the software are also shown, for comparison in terrns of harmonic distortion aJld power losses, aJld the experimental ones, with application in different load scenarios.