Investigation of the Switching States in the Asymmetrical Hybrid Cascaded Multilevel Inverter

Abstract

Cascaded multilevel inverter with unequal DC sources shows better performance in terms of the number of voltage steps at the output voltage than with equal DC sources, since the number of steps is higher when using unequal DC sources. Therefore, the output voltage waveform is improved and become closer to the sine wave. This in turn will reduce the harmonic content in the output waves. However, obtaining a separate DC source in every single cell in the inverter is difficult and costly, especially these sources are not equal (have different values) according to the used voltage ratio. Thus, hybrid cascaded multilevel inverter could offer a good solution, by using only one DC source and replacing the other sources with capacitors. However, a key challenging of this transformation is regulating the voltage of these capacitors at the specified values. This paper examines the significance of switching states redundancies of the voltage ratios on the capacitors balancing. Hence, a three-cell hybrid cascaded multilevel inverter with different voltage ratios has been modeled and simulated.