Constant common-mode voltage strategies using sigma-delta modulators in five-phase VSI

Abstract

This paper proposes and studies different sigma-delta () modulation strategies for obtaining a constant common-mode voltage (CMV) by eliminating the CMV level transitions in a five-phase voltage source inverter (VSI). These techniques are based on choosing vectors that generate a constant CMV with values of 0.1Vdc or 0.1Vdc. Because of the high-switching frequencies used with wide-bandgap semiconductors, pulse-width modulation (PWM) techniques continually generate high dv/dt values. Therefore, the proposal to combine a modulation strategy with vector selections achieves: 1) a constant CMV level due to the elimination of its level transitions; 2) a reduction in conducted electromagnetic interference; and 3) a high-efficiency converter operation. The average number of switching per transistor of the VSI is analyzed using the results from Matlab/Simulink and PLECS simulations. Experimental results are obtained by applying the proposed modulation strategies on a VSI with silicon carbide (SiC) MOSFETs. The results demonstrate the achievement of the aforementioned features.