Low frequency oscillations of hydroelectric power plant

In a hydroelectric power plant, a concern is the small-signal stability of the hydro governors and turbines on the damping of low frequency modes of oscillation. During the design stage of such plant, it is necessary to establish that the generator hydro governor and turbine do not contribute to low frequency oscillation phenomena. This paper describes a study in which a basic approach of assessing the small signal stability of a single generator hydroelectric power plant is examined by reproducing a swing frequency that is related to the low-frequency oscillation of a classical generator connected to an infinite bus (Single-machine Infinite Bus, SMIB). The development, parameters and assumptions of the SMIB test system model implemented in Digsilent PowerFactory are presented. Modal analysis is carried out and the observability modes (right eigenvectors) are calculated and used as the index of the small signal stability analysis. Complementary time domain simulations are carried out to provide a graphical representation of the modal analysis results.