Theoretical spectra of space-vector-modulated waveforms

Abstract

The authors present important new closed-form expressions for the harmonic components of space-vector-modulated waveforms. These expressions are considerably more compact than those previously published. The analysis is a direct extension of the well known geometric-wall-model method used to good effect in the analysis of asynchronous sinusoidal modulation schemes. The models and expressions developed in the paper are valid for the inherent regularly sampled characteristic of digital-space-vector modulation and for both symmetrical and asymmetrical sampling. The developed expressions for the harmonic amplitudes are valid only over the continuous-modulation range of the inverter. The analysis successfully predicts the complete suppression of certain harmonic sidebands and resultant superior harmonic performance that is characteristic of asymmetrically sampled modulation schemes. Similar expressions for the harmonics of a single-edge space-vector-modulation strategy are also developed. The occurrence of undesirable low-order harmonics of the modulating frequency for the different schemes is also discussed. The predicted harmonic spectra are completely verified by comparison with measured results from an experimental digital-signal-processor (DSP)-based modulator.