Bifurcation of Voltage Stability Limit in Direct Computational Approach

Abstract

The Jacobian matrix of load flow equation becomes singular on the voltage stability limit of a power system network. This fact is generally used to solve the voltage stability problems in direct manners. It is assumed that the demand in each load node makes increase simultaneously as the total system load makes increase in order to search the stability limit.
This paper discusses the parametric bifurcation which is occurred in this direct computational approach. As an example, if the distribution factor of demand in each load node reaches its bifurcation point, a catastrophic change of the stability limit condition will be observed in the specially composed network. This paper proposes that such parametric bifurcation will be detected to utilize the normal plane vector of Jacobian matrix. Some example systems are used to demonstrate the selection of parameter and its bifurcation aspects. These examples show that the power system network will be separated into the tight part and the marginal part from the voltage stability viewpoints, when the parametric bifurcation exists. The feasibility study is included for applying the features of parametric bifurcation to the stability enhancing operation of the power system.