Effects of load modelling on analysis of power system voltage stability

Voltage stability is a major concern for viable system operation. Much of the work in this area has focused on the use of the P-V curve as a tool for system voltage security assessment. This paper examines the effects of different load models upon this analysis method and discusses some of its limitations. Both static and dynamic load models are considered. The relationship between the nose point of the curve, the point of system bifurcation, and the stability of different regions of the P-V curve are also examined. It is shown that the load model has a significant effect in the determination of system voltage security. In particular, the paper shows that whether a system loses stability by a Hopf bifurcation is very dependent upon the load dynamics. Additionally, an analysis technique is discussed for quantifying the voltage security of a power system.