Algoritmo computacional para análise de estabilidade transitória em sistemas elétricos de potência considerando faltas assimétricas

Abstract

In general, the transient stability problem is concerned with the ability of the power system to remain in synchronism when subjected to a severe disturbance, such as a short circuit on a transmission line. The focus of this work was the transient stability analysis considering unbalanced faults, more precisely the following types of shortcircuits: single line-to-ground, line-to-line and double line-to-ground. The goal is to present a computational algorithm for analysis of transient stability considering unbalanced faults and that can also be used to analyze balanced faults. Such algorithm is simple to implement and take advantage of many of the traditional routines used in stability programs that consider only three-phase short-circuits. For the computational implementation, the MATLAB® software was used, where the dynamic behavior of the synchronous generators was modeled by differential equations, and the electric network (transmission system) was modeled by algebraic equations. The network representation during the fault was made through symmetrical components, to contemplate both unsymmetrical and symmetric faults. From the algorithm developed, which was presented through flowcharts, results of unsymmetrical fault simulations were presented to verify the effect of the same on the synchronism of the synchronous machines. Besides that, the algorithm calculated the maximum time for the protection of the system to avoid that the fault causes the loss of synchronism between synchronous machines. This time of elimination was used to measure the severity degree of the disturbances and, with that, classify and compare them. The results showed that the different types of faults studied follow the severity order for the electrical systems studied in this work: three-phase short circuit; double line-to-ground short circuit; line-to-line short circuit; And single line-to-ground short circuit. Furthermore, they also showed that the point of occurrence of the fault and, consequently, the configuration of the system after its elimination (post-fault system) was determinant to have or not a stable equilibrium point for the post-fault system and thus have critical opening time.