On the effect of the machine saturation on SSR in power systems

A bifurcation analysis is performed to investigate the influence of iron sa turation on the complex dynamics of a heavily loaded single-machine-infinit e-busbar pouter system modeling the characteristics of the CHOLLA #4 genera tor with respect to the SOWARO station. The system has five mechanical and two electrical modes. The results show that as the compensation level incre ases, the operating condition loses stability via a supercritical Hopf bifu rcation. As a result, the power system oscillates subsynchronously with a s mall limit-cycle attractor. The instability is due to the interaction of th e subsynchronous electrical mode with one of the torsional modes. When the machine saturation is considered, again, the system loses stability via a s upercritical Hopf bifurcation; however, it occurs at a slightly lower level of compensation, indicating that the influence of machine saturation is sl ightly destabilizing.