Generalized Vector Locus Transformation for Unbalanced Three-Phase Systems

Abstract

Coordinate transformations significantly simplify power systems computations. Most notably, the classical Clarke and dq0 transformations are widely used in three-phase systems, as together they transform balanced abc quantities into constant-valued signals. However, during unbalanced operation, the utility of these transformations diminishes, since a null 0 coordinate cannot be ensured and oscillating signals emerge. While recently proposed transformations ensure a null 0 coordinate, they still do not lead to constant-valued signals in the dq0 domain. In this letter, we propose a generalized vector locus transformation that ensures both a null 0 coordinate and constant-valued signals. Moreover, we show that, in the balanced case, the classical amplitude-invariant Clarke transformation is an instance of the proposed transformation.