Development and Application of a New Voltage Stability Index for On-Line Monitoring and Shedding

Continuous assessment of voltage stability is vital to ensure a secure operation of the power system. Several voltage stability indicators have been developed in an attempt to quantify proximity to voltage collapse. Some of them are computationally expensive, whereas others are reported not to perform as expected under all conditions. This study proposes a new normalized voltage stability indicator called the P-index that is robust and based on solid theoretical foundations. The index was tested on the IEEE 14-, 57-, and 118-bus systems and compared to the well-established L-index node-based indicator. It was also shown how the P-index can be used to estimate distance to collapse and the amount of load to be shed. A comparison of distance to collapse was made with the coupled single-port circuit and tangent vector methods. Application of the P-index to a dynamic platform simulating stability monitoring with PMU measurements was performed on the Kundur 10-bus system and the appropriate load shedding using the P-index was calculated. The results show that the P-index gives a better indication of proximity to voltage collapse compared to the L-indices and tangent vectors and is more conservative than the coupled single-port circuit method. Results also indicate its potential for dynamic voltage stability assessment and load shedding purposes.