A Generalized Discontinuous PWM for Three-Level NPC Inverter Over Full Power Factor Angle

The advancement in modulation strategies has significantly reduced switching loss in three-level neutral-pointclamped (3L-NPC) converter. However, conventional three-level discontinuous pulse width modulation (DPWM) methods, such as DPWM0-DPWM3, lack a generalized expression of the zerosequence voltage, which can only attain switching loss optimization under specific power factor(PF) conditions, ranging from 30° lagging to 30° leading. This paper first proposes a unified expression for conventional DPWM strategies through the comprehensive investigation of redundant small vector distributions. Based on the modulation angle, a generalized DPWM strategy is developed to minimize switching loss across full power factor ranges, particularly under low modulation index operating conditions. Finally, simulations are carried out to verify the effectiveness and superiority of the proposed method.