Random load fluctuations and collapse probability of a power system operating near codimension 1 saddle-node bifurcation

TL;DR

This paper analyzes how stochastic load fluctuations near a saddle-node bifurcation can lead to voltage instability and system collapse, providing new indicators and control strategies for early warning and prevention.

Contribution

It explicitly calculates autocorrelation functions near bifurcation points and introduces a real-time indicator for collapse risk using PMU and SCADA data.

Findings

Critical slowing-down observed near bifurcation.

New indicator function signals proximity to collapse.

Control strategies can reduce collapse probability.

Abstract

For a power system operating in the vicinity of the power transfer limit of its transmission system, effect of stochastic fluctuations of power loads can become critical as a sufficiently strong such fluctuation may activate voltage instability and lead to a large scale collapse of the system. Considering the effect of these stochastic fluctuations near a codimension 1 saddle-node bifurcation, we explicitly calculate the autocorrelation function of the state vector and show how its behavior explains the phenomenon of critical slowing-down often observed for power systems on the threshold of blackout. We also estimate the collapse probability/mean clearing time for the power system and construct a new indicator function signaling the proximity to a large scale collapse. The new indicator function is easy to estimate in real time using PMU data feeds as well as SCADA information about fluctuations of power load on the nodes of the power grid. We discuss control strategies leading to the minimization of the collapse probability.