Studies on VIPI based control methods for improving voltage stability

Based on the concept of Voltage Instability Proximity Index (VIPI) proposed by Y. Tamura et al., this paper develops two control methods for improving voltage stability. The first method maximizes the value of VIPI by using a Successive Quadratic Programming (SQP) method to find the optimal controls under various system conditions. The second determines the controls needed to maintain the specified threshold value, based on the sensitivities of VIPI with respect to control variables. The controllers used in these methods are transformer tap changers, static capacitors, SVCs and generator terminal voltages. The proposed methods have been tested for a 6-bus power system, and successful results have been obtained.