power system;  Voltage stability;  Hopf bifurcation;  bifurcation of the period;  The torus bifurcates

The nonlinear dynamic bifurcation analysis method and software are applied to analyze the voltage instability caused by saddle junction bifurcation, and the bifurcation analysis is carried out for a typical 3-node power system based on WALVE comprehensive load model. The analysis process shows that subcritical Hopf bifurcation or supercritical Hopf bifurcation may occur when different generator models are used in the same power system. At the same time, two different ways for the system to move towards voltage instability are given: continuous bifurcation through chaos and torus bifurcation due to torus rupture to voltage instability. The evolution process of voltage instability caused by two methods was studied by using the time domain simulation method.