Comparative Analysis of Standard Cascaded H-Bridge and Improved Switched Capacitor Multilevel Inverter
The demand for higher power quality in industrial applications led to the replacement of two stage inverters with multilevel inverters, which may provide multiple steps of ac output voltage with lower harmonic content. They can thus be utilized in high-voltage and high-power applications. Cascaded H bridge inverters are one of the most used multilevel inverter techniques. Yet as the number of output levels rises, H-bridge inverters use more voltage sources and switching devices, which is one of their main drawbacks. As a result, switching stress and losses rise. In this paper, a modified structure of a switched capacitor multilevel inverter (SCMLI) supplied from a single DC source and requiring fewer switching devices is compared to a conventional cascaded H-bridge inverter. This paper also presents the total harmonic distortion (THD) comparison of 9 levels, 17 levels, and 33 levels of switched capacitor and conventional cascaded H-bridge multilevel inverters. The THD of 9 levels, 17 levels, and 33-level conventional cascaded H-bridge inverters is 14.2, 13.2, and 7.5 respectively. By introducing the modified topology of a switched capacitor multilevel inverter the THD is reduced to 12.57, 9.59, and 4.4 respectively. From the comparison study, the modified SCMLI configuration is considered the most efficient topology with self-balanced voltage capability, a lesser number of switches, and reduced harmonics.
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