Voltage security assessment of large power systems using modal analysis

This paper investigates the applicability of voltage security evaluation of large power systems using modal analysis approach. The relative proximity to voltage insecurity is obtained by generating least Eigen values of system reduced Jacobian matrix at different operating conditions. The reduced Jacobian matrix directly relates the bus voltage magnitude and bus reactive power injection. The associated Eigenvector together with bus and branch participation factors identifies the critical buses and branches in each of the insecurity modes. Absolute measure of active power transfer limit and secure voltage limits of the critical bus is determined using P-V curve analysis, and that of reactive power margin from the operating point to the insecurity point is estimated using V-Q curve analysis. The weak buses are selected as the best locations for applying remedial actions to enhance the security margin. The results presented in this paper are obtained using a MATLAB based computer program. Test results of security evaluation using Western System Co-coordinating Council (WSCC) 9-bus system and IEEE 30 bus system are presented to show the effectiveness of the given approach.