A new efficient unified strategy to compute voltage collapse point and voltage stability enhancement by generation shift

A new efficient, robust and unified strategy is presented to compute the saddle node bifurcation (SNB) by the combined use of the continuation power flow (CPF), point of collapse (PoC) method and the method of a pair of multiple load flow solutions (PMLFS) with Lagrange interpolation utilizing only their advantages. The approximate nose curves and critical loading is determined fast by interpolating two stable and two unstable solutions using the PMLFS and robust CPF, and the exact SNB is computed using the quadratically converging PoC method. The proposed method is so efficient that computation time for determining the SNB in Korea Electric Power Co. (KEPCO) 791-bus system is about 24 sec in PC with Pro-Pentium processor, 166 MHz. Presented is also an improved direct method for calculating the closest SNB (CSNB) where the structure and size of the nonlinear systems equations is the same as those of the PoC method. It is shown with Klos-Kerner 11-bus system that voltage stability may be improved significantly by shifting generations in the direction of the left eigenvector at the CSNB