Centralized Adaptive Load Shedding Methods to Enhance Power System Voltage Stability Margins

In this paper, several centralized adaptive methods to determine the best location of loads to be shed, during under-frequency conditions, are proposed. The objective of these methods is to enhance voltage stability margins of the power system. Sometimes, after initial frequency drop due to some abnormal events, system frequency might return to its acceptable values, however, the system eventually becomes unstable due to voltage problems. Therefore, enhancement of voltage stability margins may help the system to preserve its stability following severe combinational disturbances. In the proposed algorithms, selection of loads to be shed depends on the location of the disturbance. The decision-making system in the control center selects appropriate loads to be shed based on the location of the tripped generator. The proposed methods are tested using two different power systems. Complete distributed models of the power systems are used in this work. The effect of the proposed methods in enhancing voltage stability margins are verified by several simulations under different operating conditions. The performances of these adaptive methods are compared with one another and also with the conventional method. Finally, time domain analysis verifies performance of the proposed methods. (C) 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.