Aplicações de estimação de impedância por método ativo em redes de distribuição

Abstract

Currently, the use of nonlinear loads and power electronics-based equipment in residential, commercial and industrial installations is contributing to the signi cant increase in harmonic distortion in electrical signals. The continuous increase in the levels of harmonic distortion in distribution grids has caused concern in both utilities and system customers, as the presence of harmonic sources may result in reduced e ciency of generation, transmission and utilization of electricity. Given this scenario, the present work presents an invasive quantitative method using the harmonic impedance of the network to determine the responsibility for the emission of harmonic distortion at a given point of the electrical system. Another important point in distribution networks is distributed generation, which is considered an alternative to solve energy and environmental problems. A grid with multiple connected distributed generators can improve energy e ciency and mitigate impacts on the grid. A problem that arises is when the main power supply is disconnected from the system, then an islanding is said to have occurred. Islanding in electrical systems containing distributed generation occurs when part of the utility grid becomes electrically isolated from the utility and the isolated subsystem continues to be powered by distributed generators. It is important to detect this condition, which can, for example, lead to problems such as power quality changes and out-of-sync automatic reclosing, causing irreversible damage to utility equipment. Thus another purpose of this work is to identify the islanding by the variation of the system impedance, for this an active method was developed that injects small signals in the distributed generator output to estimate the system impedance. To test the proposed methods di erent platforms were used, in these several cases were performed that showed the accuracy of the results found.