A circuit approach for the propagation analysis of voltage unbalance emission in power systems

In this work an approximate circuit model is derived to describe the impact of mutual coupling between sequence circuits in a three-phase power system including an asymmetrical line (e.g., untransposed line). The proposed equivalent circuit exploits the assumption of weak coupling between positive and negative sequence circuits. This hypothesis proves to be reasonable since line asymmetry can be usually considered as a small perturbation of symmetry. Since the derived equivalent circuit is very simple, it can be effectively used to investigate propagation of voltage unbalance emission through a complex power network. The proposed circuit model is validated through a Simulink® numerical simulation of a three-phase power system including a stretch of asymmetrical line.