  How to determine the vector of power supplies of a stochastic power system
for the next short horizon, such that the probability is less than a
prespecified value that any phase-angle difference of a power line of the power
network exits from a safe set? The power system is modelled such that the
differential equation of each frequency is affected by a Brownian motion
process. A safe set can be selected to be any subset of the interval $(-\pi/2,
~ +\pi/2)$, which is a sufficient condition for not losing synchronization.
That the controlled system has an improved performance is shown by numerical
results of three academic examples including a particular eight-node academic
network, a twelve-node ring network, and a Manhattan-grid network.
