Optimal allocation of FACTS controllers for critical loading margin enhancement

Currently, most of the power systems operate under deregulation environment. This mode of operation leads the power systems in to unpredictable and sometimes unsecured states with the competition among market participants in addition to the uncertainties. The maintenance of acceptable range of bus voltage magnitudes and transmission congestion management are become essential preventive tasks to the system operator to drive the competitive electricity market schedule. Due to the lack of reactive power support and transmission system capacity, the networks could also subject to voltage instability. In order to improve the transmission system loadability even under line outage contingencies, this paper addressing the application of flexible ac transmission system (FACTS) devices. Based on the impact on critical loading margin (CLM), the contingencies have been ranked. The critical loading margin is determined using repeated power flow (RPF) method and possible improvement is achieved with various FACTS devices in the network. SVC, TCSC, TCPST and UPFC devices have been considered to install in the network.