Voltage stability and controllability indices for multimachine power systems

This paper presents a voltage stability index (VSI) and a voltage controllability index (VCI), related to the eigenvalues of m x m matrices in a multimachine power system made up of m synchronous generators and a number of infinite buses. System loads can have an arbitrary voltage sensitivity described by generalized voltage exponents. These nonlinear loads are linearized around an operating point and incorporated into a modified “admittance” matrix, which is subsequently reduced to the generator terminals using an efficient algorithm and sparsity techniques. The indices proposed are tested in a practical power system and it is demonstrated that they provides a timely warning during a sequence of events leading to voltage collapse