Multilevel inverters have gained significant attention in modern power electronic systems due to their ability to generate high-quality voltage waveforms with reduced harmonic distortion and lower switching stress on semiconductor devices. Total Harmonic Distortion (THD) is a key parameter used to evaluate the quality of the inverter output voltage. This paper presents a comprehensive analysis of voltage THD in single-phase and three-phase multilevel inverter configurations. Various inverter topologies including diode-clamped, flying capacitor, and cascaded H-bridge multilevel inverters are discussed. In addition, commonly used modulation techniques such as Sinusoidal Pulse Width Modulation (SPWM), Space Vector Pulse Width Modulation (SVPWM), and Selective Harmonic Elimination (SHE) are analyzed with respect to harmonic reduction capability. The study evaluates the effect of increasing the number of voltage levels on the harmonic content of the output waveform. Simulation results demonstrate that multilevel inverter systems significantly reduce THD when compared with conventional two-level inverters. The proposed analysis provides insight into the design of efficient inverter systems suitable for renewable energy integration, motor drives, and high power industrial applications.
