  This paper investigates a multilevel inverter with a capability that produces
a wide voltage range with high quality. The selective harmonic elimination
(SHE) method is considered for a single-phase 5-level cascaded H-bridge (CHB)
inverter, in which the particle swarm optimization (PSO) algorithm solves the
nonlinear equations. However, eliminating the low-order harmonics has been
challenging when a low range of output voltage is required. To surmount such
challenges and access to a wide range of output voltage, an adjustable dc-link
is introduced that allows the inverter to increase the modulation index,
resulting in a significant decrease in total harmonic distortion (THD). In this
paper, to regulate the dc-link voltage amount, a 12-pulse rectifier is employed
to allow the inverter to produce the output voltage requirements with less
distortion. To prove such claims, the PSO algorithm is modified to calculate
the optimal angles, as a result, the switching angles are applied in SIMULINK
MATLAB to generate a 5-level output voltage.
