An Approach to Natural Sampling Using a Digital Sampling Technique for SPWM Multilevel Inverter Modulation

Abstract

This paper introduces an approach that applies a digital sampling technique for a sinusoidal pulse width modulation (SPWM) multilevel inverter modulation that reduces the total harmonic contents in the output voltage compared to that of classical regular sampling techniques. This new modulation emulates with a high degree of fidelity a natural sampling pulse width modulation (PWM). The theoretical analysis of this new digital technique compared with natural sampling has been validated by simulations and through experiments with a built prototype that performed five−level inverter modulations with vertically displaced carriers in phase disposition. Both simulation and experimental results generate a SPWM output voltage with higher fidelity than classic regular sampling techniques, allowing a reduction of the filtering demands on the inverter output, which in turn can decrease the converter size and its manufacturing costs. As the presented technique is digital, the resulting modulation is more robust against switching noise, jitter, and other system perturbations and the modulation parameters can be changed easily, even in an automated way. For this reason, the modulation introduced here can be a useful tool to perform spectral analysis for different multilevel modulations and systems.

Keywords

• carrier shape ratio
• level distribution
• multilevel inverter
• phase disposition
• sampling methods