Comparison of OMTHD and OHSW harmonic optimization techniques in multi-level voltage-source inverter with non-equal DC sources

One of the major problems in electric power quality is the harmonic contents. There are several methods of indicating the quantity of harmonic contents. The most widely used measure is the total harmonic distortion (THD). This paper compares the two harmonic optimization techniques, optimal minimization of the total harmonic distortion (OMTHD) technique and optimized harmonic stepped-waveform (OHSW) technique used in multi-level voltage-source inverters. Both techniques are very effective and efficient for improving the quality of the inverter output voltage. First, we describe briefly the cascaded H-bridge multi-level inverter structure. Then, we present the switching algorithm for the inverter based on OHSW and OMTHD techniques. Finally, the results obtained by simulation for the two techniques are analyzed and compared. Simulation results verify the effectiveness of the both techniques in multi-level voltage-source inverter with non-equal DC sources, clarifying the advantages of each technique.