Cálculo de equivalente de rede elétrica para avaliação do risco de instabilidade de tensão em tempo real por meio de curvas PV e VQ

Abstract

This dissertation aims at the development of a methodology for determining network equivalents that are suitable for performing voltage stability assessment in real-time through PV and VQ curves. In order to meet this objective, two research lines were identified: the estimation of network equivalent parameters as seen from a chosen bus, and the voltage stability assessment based on the network equivalent approach. Along the first line of research, the main advance demonstrates that the modelling of the generator in the network equivalent significantly influences the risk of voltage instability. The parameters of the generators are obtained by the solution of a restricted nonlinear optimization problem that provides the voltage source, and the reactances in direct and quadrature axes. These reactances are included in a modified nodal admittance matrix. On this matrix, the domain decomposition method is applied for selecting the busses that will be monitored, as well as to reduce computational cost. Additionally, considering the vast literature on the subject of network equivalents for real-time applications and the lack of simulations in the environment in which they are proposed, a comprehensive investigation of this set of methodologies is presented. Following the second line of research, voltage and reactive power margins that consider a predetermined distance to the voltage instability point on PV and VQ curves are proposed. The joint analysis of these margins provides clearer evaluations than those derived through the traditional methodologies, in relation to the risk of voltage instability. The studies in this research are carried out on standardized networks created by the Voltage Stability Task Force.