Weakest Buses Identification and Ranking in Large Power Transmission Network by Optimal Location of Reactive Power Supports

The detection of voltage collapse is essential to avoid possible voltage collapse for the preventive control actions and voltage security assessment. One effective way to know the locations where voltage collapses could be appear is to identify weakest buses in the systems. The weakest bus is the first point where voltage collapses appear in a severe contingency. This paper proposes a technique to evaluate the weakest bus in large scale power system based on the optimal position of reactive power supports. To solve the optimization problem, Differential Evolutionary (DE) technique is used. The fitness function consists of cost, power losses and Load voltage stability index (Lmn) which satisfying all operational constraints. Lmn is used as the indicator for voltage stability margin and weakest bus identification. The method is applied on standard IEEE 30 bus, 57 bus and 118 bus test systems to show their comparative computing effectiveness.