Harmonic reduction in CHB 13-level inverters by PAM fundamental-frequency strategy

In this paper cascaded H-bridges (CHB) 13-level inverters are considered and a particular pulse amplitude modulation (PAM) strategy is introduced to mitigate or eliminate many harmonic components on the output voltage, in order to obtain low Total Harmonic Distortion (THD) factor. This procedure defines different dc voltage sources and sets of six switching angles, depending on an integer parameter q belonging to the close interval I=[11, 15]. The obtained THD doesn't depend on modulation index m. The control of m is made by changing the dc voltage sources that depend linearly on m, while the switching angles remain constant. An investigation about the role of the q parameter on the performances of the CHB 13-level inverter, in terms of mitigated/eliminated harmonics and THD, is shown.