In this paper, an oscillation center fast positioning method and the criterion that determines whether a system is out-of-step are combined together to put forward a compound oscillation center positioning and splitting criterion with predicting function. Simulation of a classical numerical example of four-machine system in two regions and an actual example of central China-north China power grid proves that this method can pre-locate lines where oscillation center lies after out-of-step operation of the system when the system is oscillating intensely but still keeps synchronized.

In order to prevent voltage collapse while the voltages drops, adopts under voltage load shedding (UVLS) clustering control to recover voltage stability. First using the method of sensitivity sorting to cluster the load node, then using PV curve to calculate and determine the number of loads to be shed, finally the same cluster taking the same control parameters to shed the loads, the simulation validate it could recovery voltage stability and embodies the rationality and economical efficiency of this method.