Comparison on modulation schemes for 15-level cascaded H-bridge multilevel inverter

Abstract

In series with each other, the cascaded H-bridge multilevel inverter (CHML) could apply same or different DC bus voltage. By modifying the isolated DC voltage supplies of a traditional 7-level 3H-bridge inverter with voltage ratio 4:2:1, the proposed inverter outputs a near-sinusoid, 15-level resoluted, stepped voltage with low distortion. The pros and cons of different modulation schemes including PWM, staircase modulation and hybrid PWM are analyzed on switching losses, low order harmonics and THD, which are then verified by Saber simulation.