In this paper, we study the complex nonlinear phenomena in a fundamental power system provided by paper, We analyze local stability and bifurcation of equilibriumin the dynamics systems. When $0
\frac{V^2_s(X_d-X_d')}{2X_{d\Sigma'}X_{d\Sigma}}$ and withcontrol$u_f>E_{fdsc}
+u_{fc}-E_{fds}$ , there are two fixed points, one is stable, the other is always unstable. $E_{fds}+u_f=E_{fdsc}+u_{fc}$is saddle-node bifurcation value corresponding to collapse of the power system. As$E_{fds}+u_f