  In recent years, the use of multilevel inverter has become popular due to its
many advantages. Due to the popularity of multilevel inverters in industries
and in applications that require a wide range of voltages, there have been many
challenges to achieve high-quality voltage. Many pieces of research have been
done to solve the problem of annoying harmonics in multilevel inverters. In
this study, pulse width modulation (PWM) has been proposed as a switching
method. Using the Selective Harmonic Elimination (SHE) technique, the inverter
switching can be carried out in low frequency, and also, this method can reduce
the annoying harmonics significantly. However, in the lower modulation index,
eliminating such harmonics is challenging, resulting in a considerable increase
in output voltage distortion. This study suggests a way to solve the problem.
In this research, eliminating selected harmonics in a multilevel inverter with
variable DC links is proposed. The DC-link variable method in this study is to
use a high-frequency isolated DC-DC converter. The proposed method is verified
on a 5-level Cascaded H-Bridge (CHB) inverter using the SHE-PWM method solved
by particle swarm optimization (PSO) algorithm.
