Research on internal relation between virtual space vector pulse width modulation strategy and carrier sinusoidal pulse width modulation strategy for

In the modulation strategies for three-level NPC converter, neutral point voltage control under the entire modulation index and full power factor can be achieved by virtual space vector pulse width modulation (VSVPWM) strategy. In this paper the basic principle of VSVPWM is analyzed, then the internal relation between three-level VSVPWM strategy and single-phase dual modulation based three-level sinusoidal pulse width modulation (SPWM) strategy is derived and the modulation-wave equivalence between the two modulation strategies is established. Using the established modulation-wave equivalent relation, the total harmonic distortion (THD) of output voltage, DC voltage utilization rate and switch device losses under VSVPWM strategy are analyzed. Finally, a fast implementation of three-level VSVPWM strategy based on modulation-wave equivalence is proposed. The correctness of the theoretical analysis is verified by both results from simulation and experiments.