Voltage quality comparison of space vector PWM voltage source multilevel inverter under symmetric and nonsymmetric switching sequence variants: Voltage waveforms, spectra and THD

TLDR: In this article, a simple voltage source multilevel inverter space vector PWM algorithm with the optimum three-segment non-symmetric vectors switching sequence variant was proposed, providing the instantaneous output voltage quarterwave symmetry.

Abstract: The paper offers the simple voltage source multilevel inverter space vector PWM algorithm (based on the oblique-angled coordinates of two delta voltages) with the optimum three-segment non-symmetric vectors switching sequence variant providing the instantaneous output voltage quarter-wave symmetry. The comparisons with the five-segment variant by the voltage waveforms, spectra and THD are performed under the same lowest frequency modulation index values. The offered three-segment variant advantages in the THD values and in the switching quantity per the output voltage cycle are shown via the PSIM simulation. The Mathcad-drawn executed space vector loci are also shown and the voltage THD is presented as the function of the amplitude modulation index.