Harmonic Analysis of Three-Phase Asymmetrical Multilevel Inverter with Reduced Number of Switches

This paper presents an analysis of a three-phase asymmetrical multilevel inverter towards resistive and inductive load testing. The asymmetrical multilevel inverter is chosen over the standard symmetrical multilevel inverter due to its circuit simplicity, cost-effectiveness and better performance as the topology offers a reduction in the number of switches and the improved Total Harmonic Distortion (THD). Whenever different levels of voltage are applied in an asymmetric cascaded H-bridge multilevel inverter, it will increase output voltage levels and reduces the harmonics. The selected topology is the cascaded H-bridge inverter with reduced number of switches and the modulation technique used in this paper intersects a single unit of a sine wave with three carrier signals to produce the PWM pulses for controlling the MOSFETs. The experiment was set up under a lab-scale and using the standard DC power supply. The experimental data for both resistive and inductive loads with modulation indexes of 0.7 and 0.9 are shown to verify the analysis. THD voltage and current are slightly higher for resistive loads than inductive loads. In addition, as the modulation index rises, the value of THD voltage and current decreases.