Feedback Quantizer and Non Linear Control Applied to Multi-Cell AFE Rectifier

AC-DC power conversion is an essential process in the industrial area at medium/high voltage levels for AC motor drives, conveyor belt systems, rolling mills, or others. The multilevel converters allow us to work at the voltage levels mentioned and give us a low harmonic content in the AC side of the system. However, these power conversion systems consist in their topology of an input transformer, which is sensitive to low order harmonic currents, generating saturation and increased losses. This work proposes a modulation scheme called Feedback Quantizer, applied to multi-cell active front-end rectifiers, aiming to obtain a focused mitigation of low-frequency current harmonics of the power cell. Furthermore, to ensure the stability of the DC voltage of each power cell, a control strategy consisting of nonlinear control, a first-order filter to the DC voltage reference, and a PI control will ensure stability and zero steady-state error at step input. The simulated results show the correct operation of the proposed scheme.