  This paper studies the impacts of stochastic load fluctuations, namely the
fluctuation intensity and the changing speed of load power, on the size of the
voltage stability margin. To this end, Stochastic Differential-Algebraic
Equations (SDAEs) are used to model the stochastic load variation; bifurcation
analysis is carried out to explain the influence of stochasticity. Numerical
study and Monte Carlo simulations on the IEEE 14-bus system demonstrate that a
larger fluctuation intensity or a slower load power changing speed may lead to
a smaller voltage stability margin. Particularly, this work may represent the
first attempt to reveal the influence of the time evolution property of the
driving parameters on the voltage stability margin in power systems.
