Modification of cascaded H-bridge multilevel inverter to increase output voltage level with a single DC voltage source

It presents an effective circuit configuration of multilevel inverter which can increase the number of output voltage levels compared with the conventional cascaded H-bridge multilevel inverter. The proposed multilevel inverter consists of a dc input source with a series of capacitors, diodes, active switches for synthesizing output voltage levels, and an H-bridge cell. To generate seven levels in an output voltage, the proposed approach needs 7 switches. On the other hand, a traditional cascaded H-bridge multilevel inverter needs 12 switches. It can save five active switches resulted in cost saving with increasing the output voltage levels. Moreover, it is useful to extend output voltage levels by adding more active switches or the proposed module itself. To verify the validity of the proposed approach, we carry out computer-aided simulations and experiments. Here we also introduce a switching scheme to solve voltage unbalancing problem occurred in dc input voltage source with series-connected capacitors.