Análise de estabilidade em regime permanente de sistemas elétricos susceptíveis a ressonância subsíncrona

Abstract

Subsynchronous resonance is a phenomenon inherent in electrical power systems which presents thermal power plants connected to series compensated transmission networks. This phenomenon is characterized by energy exchange between turbine generator shafts and the transmission system at frequencies below the synchronous one, i.e., at subsynchronous frequencies. Therefore, to capture this phenomenon it is necessary to model generators, turbine-generator mechanical shafts and electrical network, so that the network frequencies can be reflected on mechanical shafts through the electromagnetic torques induced in the generators and vice-versa. This effect becomes critical when one of the network natural frequencies is close, or equal, to one of the torsional modes of the shafts. Under these conditions, the system may come to be self-excited or even unstable. This document intends to present, in a comprehensive way, alternative forms to interpret the subsynchronous resonance and its build-up mechanisms. It also exposes models for the basic components of the electrical power systems for subsynchronous resonance studies, among them synchronous generators, electrical network and mechanical shafts. The eigenanalysis are employed as the main tool for the stability analysis in this document, which are based in the linearised state space matrix of the whole system. An index designed to identify Hopf bifurcations in electrical power systems is also presented, aiming a quick visualization of the system critical points, when a specific control parameter is varied. In the end of the dissertation, some numerical examples are presented, providing one to reproduce them totally.