A Novel Analytical Study on Voltage Instability Mitigation Using Multiple Severity Functions by Optimal Placement of SVC in N-2 Contingency Analysis Using Gravitational Search Algorithm

Voltage stability analysis based on the number of limit violating buses apart from considering the voltage magnitude violations using several severity functions is performed in this work. Deviating from existing works in literature, the double line contingency is considered based on the three types of severity functions: discrete, continuous and percentage of violation severity functions. The severity functions are analyzed and their merits and drawbacks are discussed. The N-2 line outage comprising of all the 820 possible combinations of contingency states in the IEEE 30 bus system is effectively analyzed and contingency ranking is done based on the severity. FACTS devices are utilized to improve the voltage profile of the system during line outages. The Static VAr Compensator (SVC) is considered here, as the compensating device. A multi-objective optimization, with the objective of minimizing the voltage deviation and also the number of limit violating buses with optimal reactive power support is achieved through the Gravitational search algorithm (GSA). The effectiveness of the proposed work is tested on IEEE 30 bus system under double line contingencies. The results of the work are compared with several optimization methods and the results substantiate the effectiveness of the proposed methodology. Key-Words: Voltage Stability, Severity Functions, N-2 line contingency, FACTS, Static VAr Compensator, Gravitational Search Algorithm.