Analysis and comparison of conduction losses in neutral-point-clamped three-level inverter with PWM control

The three-level inverter system is promising in AC drives, especially in the medium to high power range. With conduction losses evaluation being a significant concern, an extensive study on it can be a considerable benefit. This paper investigates the conduction losses for neutral-point-clamped (NPC) three-level PWM voltage source inverter, and presents an effective and straightway conduction-loss-analysis method. The conduction losses expressions are derived based on the knowledge of conduction devices, which are determined by the working condition, and the conduction duty cycle. This method can be utilized to calculate conduction losses for different PWM modulation strategy. Sinusoidal PWM (SPWM), third harmonic injection PWM (THIPWM), and space vector PWM (SVPWM) techniques will be discussed with the calculations for conduction losses in the transistors, diodes and the control system. Some interesting conclusions can be come to according to the simulation results. This approach should benefit the prediction and further investigation of power semiconductor losses for multilevel inverter.