Bifurcation mechanism of low-frequency oscillations in power systems with long transmission lines

Low-frequency oscillations have long been observed in power systems with long transmission lines. However, the underlying mechanism that leads to these oscillations has not been identified clearly so far; that is, the close connection between transmission distance and occurrence of oscillations has not been verified. As known by power engineers, low-frequency oscillations are the heart flutters of the power grid. Accordingly, fundamental understanding of the mechanism of these oscillations is of crucial importance. Our work addresses the bifurcation mechanism of the low-frequency oscillations that results from long-distance transmission. Analyzing the dynamical model of a sample two-machine power system with transfer conductance under changing the length of transmission lines via simulations by MATLAB and SIMULINK, we have come up with the mechanism of subcritical Hopf bifurcation, which results in low-frequency oscillations growing in amplitude. In this paper, we present our results regarding these oscillations.