Small Signal Stability Analysis of Power System with Implicitly Restarted Arnoldi Algorithm

South China Power System is a typical AC-DC interconnected power system. This paper presents the results of small signal stability analysis of South China Power System with a sparse eigenvalue analysis method-IRA, which has fast convergence. The countermeasures are selected after the weak damping modes are found: such as adding PSS on generators with high participation factors and applying HVDC modulation. It shows that the system damping can be increased and the low frequency oscillation can be suppressed by PSS and HVDC modulation.