Reduction of parasitic spectral components of digital space vector modulation by real-time numerical methods

This paper presents the analysis of the voltage error caused by a finite resolution of the modulator of a three-phase PWM invertor. A suitable algorithm is proposed in order to eliminate offsets and to reduce parasitic components for as much as 15 dB. Essentially, the algorithm represents the numerical procedure of rounding the high-resolution amplitude products into lower resolution digital words that are to be loaded into the PWM counters. For a given resolution of the modulator, the suggested procedure considers the coupling between the phase residual errors and selects counter loads in such a way that the minimum voltage vector error is obtained. The presented analytical considerations are verified by experimental results. The spectra of the inverter output voltage, obtained in an experimental setup, illustrate the efficiency of the proposed algorithm in suppressing undesired spectral components of the inverter output.