Dual-buck inverters feature some attractive merits, such as no reverse recovery issues of the body diodes and free of shoot-through. However, since the filter inductors of dual-buck inverters operate at each half cycle of the utility grid alternately, the inductor capacity of dual-buck inverters is twice as much as H-bridge inverters. Thus, the power density of dual-buck converters needs to be improved, as well as the conversion efficiency. The detailed derivation process of two five-level full-bridge topology modeling is presented. The operation modes, modulation methods and control strategies of the series-switch five-level DBFBI topology are analyzed in detail. The THIPWM technique operates by adding a third harmonic component to the sinusoidal modulating wave. It is possible to increase the fundamental by about 15.5% and hence, allow a better utilization of the DC power supply. The power device losses of the three-level DBFBI topology and five-level DBFBI topologies, with different switching frequencies are calculated and compared. Both the relationship between the neutral point potential self-balancing and the modulation index of inverters are revealed. Simulation results have shown that the five-level series DBFBI topology exhibit higher efficiency than the five-level H-bridge inverter topology and the three-level DBFBI topology.