Voltage Stability Enhancement in Contingency Conditions Using Shunt FACTS Devices

This paper investigates the application of FACTS devices to extend voltage stability margin in electric power systems. Most of methods proposed for allocation of FACTS devices consider only the normal state of network. Nevertheless, voltage collapses usually initiated by a single contingency. Therefore, in this paper a strategy for location of FACTS devices based on contingency studies is proposed. Using modal analysis, a probabilistic index is defined which can be used to rank of system buses based on their effect on system voltage stability enhancement under all possible contingencies. It is shown that this method leads to a uniform reactive power supply in the system. Consequently, it will be effective in more contingency conditions. The IEEE 14-bus test system is used to demonstrate the proposed approach of placing shunt FACTS devices. The obtained results show that allocation of FACTS devices using the proposed approach improves the system voltage stability under contingency conditions with smaller size of FACTS to be installed compared to other methods.