A comparison of efficiency for three-level NPC and Active NPC voltage source converters

The 3L-NPC (three-level Neutral-Point-Clamped) is the most popular multilevel converter used in high-power medium-voltage applications. An important disadvantage of this structure is the unequal distribution of losses among the switches. The performances of 3L-NPC structure were improved by developing the 3L-ANPC (Active-NPC) converter which have more degrees of freedom. In this paper the switching states are studied for different PWM strategies. A numeric calculus method for the total losses in switches was also presented in order to compare the efficiency for the 3L-NPC and 3L-ANPC converters. The PSIM simulation results are shown in order to validate the analysis of the switching states.