This paper analyzes the relationship between the critical voltage stability and synchronism stability limit in power system.

The stability limit of power transmission from Shaanbei Grid to Guanzhong Grid is analyzed based on the Shaanxi Grid structure in 2006,the results show that the power delivery capacity from Shaanbei to Guanzhong Grid is restricted by the stability limit of transmission sections.

Stability limit of synchronous electric machine matches with the exciting current If and armature current IM in the stability limit area of V-curve,traditionally,there are two methods to solute the stability limit: drawing potential vector and field exploring.

To investigate the rationality of the load model currently used by Fujian power grid, the stability limits of Fushuang lines are calculated for different network structure and nodal load models of Fuzhou power network as index of Fujian power grid s transient stability level, and factors influencing load characteristics and system stability are analyzed.

Analysis on factors influencing transient stability limits of long-distance transmission profile;

Then,based on the Lagrange theory and earlier works concerning synchronous stability for 6-DOF multi-machine vibration system,a dynamic model of 12-DOF multi-machine vibration system is developed first and,on the Hamilton principle,it provides the characteristic conditions for synchronous operation and especially the synchronously stable operation.