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DC-link current harmonics are the predominant factor to be considered for dimensioning dc capacitors in three-phase pulsewidth-modulation (PWM) voltage-source converters. In this paper, an analysis of the dc-link current harmonics applying a double Fourier series is derived. The analytical results for the dc-link current spectra of continuous and discontinuous PWMs are presented and compared with measurement results taken from a converter test setup. A good match between theoretically expected and actually obtained experimental results can be stated. Moreover, characteristic differences between the investigated modulation strategies regarding their dc-link current spectra become evident.
Date of Publication: May 2008