  Up to now, many modulation techniques have been proposed for neutral point
clamped (NPC) inverters. In this paper, for the first time, a general
methodology is applied to calculate and compare the failure analysis and
reliability of NPC inverter with most commonly used control strategies. Also,
the mean time to failure (MTTF) of NPC inverter is derived for different
control strategies. It is demonstrated that the key feature of control
strategies in determining the reliability of inverter is their loss
distribution among the switches. The failure rate of components that is
relevant to this study and junction temperature calculation is developed, then
conduction losses and switching losses of switches for different control
strategies are calculated. Finally, the most reliable control strategy is
identified. Experimental results obtained have promptly justified the
theoretical analysis and outlined procedure.
