Three-phase distortion analysis based on space-vector locus diagrams

This work deals with the use of the space vector concept to characterize the harmonic content of a three-phase voltage/current. It is shown that the shape of the trajectory of the space vector on the complex plane (i.e., the locus diagram) provides information about its harmonic content. In particular, it is shown that each harmonic contributes to the locus diagram with a number of lobes depending on the relative angular frequency between the harmonic and the fundamental component. To this aim, the different contributions of positive-sequence and negative-sequence harmonics is explained and put into evidence with specific examples. The expressions for the magnitude and phase of the space vector as functions of the harmonics are derived analytically. Numerical examples are provided to show how the locus diagram can represent a three-phase quantity with positive-sequence and negative-sequence harmonics.