Consistent circuit technique for zero-sequence currents evaluation in interconnected single three-phase power networks

Abstract EN

This paper deals with a rigorous and mathematically consistent technique for circuit analysis of modern electrical power systems consisting in the interconnection of three-phase components and single-phase active loads.

Indeed, it is well known that the standard technique based on the symmetrical components transformation is commonly used in the analysis of symmetrical threephase systems.

Nowadays, however, the evolution of power systems towards the custom power conditioning (e.g., active filtering) and the smart grid model requires the inclusion into the analytical tool of single-phase active loads.

Starting from the symmetrical components transformation in its rational form instead of its classical form, a rigorous circuit representation of the interconnection of a three-phase system with single-phase active loads is derived in the paper.

The proposed circuit representation allows the analysis of complex power systems by means of basic circuit techniques.

In particular, the paper focuses on the evaluation of the zero-sequence component of the currents in any branch of the power system.

The application of the proposed circuit technique is demonstrated through an example consisting in the analysis of an active filter designed to force to zero the current in the fourth wire of the mains.