Harmonic Minimization in Multilevel Inverter Using PSO-based Soft-computing Technique

A conventional asymmetrical cascaded H-bridge multilevel inverter (CHBMLI) requires a total number of twelve power switches to generate an output voltage waveform with 15 voltage levels. In this paper, the operating principle and performance of a 15-level asymmetrical multilevel inverter (MLI) with a reduced number of power switches are presented. The 15-level asymmetrical MLI is constructed with only ten power switches, which is reduced by 16.67 % compared to the 15-level asymmetrical CHBMLI. The switching-angle calculation applied to the MLI is another important design aspect in MLI research and the switching angles must be computed properly to obtain an output voltage waveform with low total harmonic distortion (THD). In this work, a particle swarm optimization (PSO) based selective harmonic minimization pulse-width modulation (SHMPWM) technique is used to obtain the optimal switching angles applied to the 15-level asymmetrical MLI. A PSIM simulation model is developed to validate the effectiveness of the optimal switching angles applied in the 15-level asymmetrical MLI. Simulation results suggest that the 15-level asymmetrical MLI is able to produce a sinusoidal-like staircase output voltage waveform using PSO-based SHMPWM optimized switching angles at modulation index of 0.70. At the same modulation index, the performance of the 15-level asymmetrical MLI connected with different inductive loads is also validated.