Métodos de redução de sistemas de distribuição e contribuições aos estudos do limite de estabilidade de tensão e das múltiplas soluções do fluxo de potência

Abstract

It is proposed in this thesis the following methods and tools for application on Distribution Systems (DS): (i) reduction methods; (ii) a tool for analyzing the voltage stability limit and the reactive power margin; (iii) method for initializing the neutral voltage; (iv) formulation to demonstrate the existence of multiple operationally-stable solutions in DS. Firstly, it is presented the mathematical development of reduction methods of DS for the purpose of representation in analysis tools, seeking to reduce the overall computational processing time. When applying the proposed methods, the reduced system solution aims to be mathematically equivalent to the original one, for all loading levels or with a small numerical error. The developed proposals are validated in several studies, considering different characteristics of DS. Secondly, the use of the multiphase continuation power flow is expanded, establishing a new algorithm and the formulation to obtain the QV curves in threephase four-wire DS. The development of such a tool allows the evaluation of the voltage stability limit and the reactive power margin in DS. Following, it is developed a procedure for initializing the neutral voltage when solving DS, which has also allowed an improvement in the convergence of iterative power flow solution tools. Lastly, a study is carried out where the nonlinear equations of a generic two-bus DS are deduced and used to verify the existence of multiple maximum loading points in DS. It is used the Bertini tool to solve such equations under a parametric variation on the power factor of the load, grounding impedance, loading level, and unbalance level of the load, proving the existence of multiple solutions that present operationally stable values. It must be highlighted that all the developed methods, tools, and studies may assist researchers and utilities in the decision-making on several aspects related to DS.