Analysis of semiconductor power losses in M-level NPC inverters

In this paper, a power loss evaluation algorithm for M-level neutral-point clamped (NPC) PWM inverters is presented. In a three-level inverter, the conduction loss depends on the MI (modulation index) and the PF (power factor), and the switching loss depends on a switching frequency, turn-on and turn-off energy. However, in the higher level of inverters than the three-level, the modulation depth should be considered in addition since the conducting devices are different depending on the MI. In a case study, the power loss analysis for the three- and five-level NPC inverters has been performed with the proposed algorithm.