One multilevel inverter method uses independent dc sources, each with an H bridge.
A circuit with two dc voltage sources is shown in Fig. 8-9. The output of each of
the H bridges is Vdc, Vdc, or 0, as was illustrated in Fig. 8-1. The total instantaneous voltage vo on the output of the multilevel converter is any combination
of individual bridge voltages. Thus, for a two-source inverter, vo can be any of
the five levels 2V
dc, Vdc, 0, Vdc, or 2Vdc.