Propostas de metodologias para a determinação das contribuições sobre os desequilíbrios em sistemas elétricos trifásicos

Abstract

Imbalances are common phenomena on three-phase electric power systems. These anomalies may come at the expense of asymmetries inherent to networks, comprising the generation, transmission and distribution systems as well as the consumption centres. Since they can cause harmful effects upon electric power system components and operation, whether they are manifested in terms of asymmetric voltages and/or currents, imbalances must be limited according to power quality national standards. In this way, whether the limits are exceeded, mitigating approaches must be provided accordingly in order to make the levels compatible with the standard requirements. In fact, there are several imbalance compensation strategies available, which shall be used according to the nature and source of the problem. Therefore, as it may involve considerable costs, the matter of determining (or sharing) the imbalance contributions among the parts involved shows itself as relevant. This topic emerges from the need to determine the individual contributions of different disturbance sources regarding the global voltage imbalance at a given busbar. It should be noted that these sources are here defined as supplier and consumer agents. In the literature there are a number of researches focused on this matter. However, due to its complexity, as it currently stands, there is no procedure that has proved to be trustworthy simultaneously in both theoretical and practical aspects. For this reason, in addition to the updated state of the art concerning imbalance responsibility sharing, which includes pointing out and assess the most popular procedures existing in the literature, this work aims to propose two innovative strategies to address this matter. The first one is a theoretical-based principle that lies in common knowledge of electrical circuits. The second one is a practical-based approach that aims to establish means for determining voltage imbalance contributions in the field. Both propositions support each other and they may be used together. Furthermore, in order to assess the proposed methods and others, computational and laboratory studies are carried out on an electric hypothetical system with a strong motor load. In fact, this characteristic seems to be a relevant influence factor in qualitative studies.