Its a simple model simulation of an npc inverter(also called as diode clamped multilevel inveter),its called as multilevel inverter because of its stepped output in this case 3 level ,here modulation/control strategy used is spwm (with triangular level shifted control signals and sinusoidal phase shifted signals),the result of line voltages Vab,Vbc,Vca are shown , NOTE: the phase voltages are of 3 levels (i.e voltage across each leg or phase ) whereas the line voltages are of 5 levels ,hence the name multilevel inverter .the load that is used here is RL.