O uso da técnica dos grafos de ligação para a simulação de centrais hidrelétricas em regime transitório

Abstract

The simulation of transient phenomena in pipes and hydroelectric power plants, using standard software based on the Bond Graphs approach, is investigated. The Bond Graphs modeling takes advantage of the power exchange and the analogies between the hydraulic, mechanic and electrical subsystems, permits to describe the major nonlinearities of the components, and can be used to simulate the small and large transient response. A survey about the most suitable software for academic use is presented. The modeling of conduits through lumped parameters versus distributed ones is analyzed. The simulations of water hammer in two simple systems composed of reservoir, conduit and valve, give quite accurated results from the practical point of view when compared with simulations with the Method of Characteristics and experimental results. Finally, a new model of hydraulic turbine as a nonlinear transformer is proposed and a model of efficiency, electric load and governor are developed. This modeling is used to simulate partial and total load rejection and load acceptance in two isolated electrical power systems: a case extracted from classical literature and a recent study of Santa Clara Hydroelectric Power Plant in Minas Gerais, Brazil. The comparisons of speed and pressure transients with another methods and specialized software confirmed the validity of the turbine and the others components modeling.