Flexible AC Transmission System (FACTS) have been recognized to be effective in regulating network power flow and enhance system dynamic performance. In this paper, multiple UPFCs are integrated into a network and controlled according to the Max Flow algorithm to avoid possible cascading line outage. The dynamic response of UPFC controllers and generator performance are investigated with potential cascading critical line outage. Cascading blackout prevention is investigated not only for steady state power flow overload problem but also for system dynamic stability problem. Generator performances of speed deviation, angle deviations and bus voltage profile as well as dynamic power flows are shown. A classical generator model is used in the simulation program. The IEEE 118-bus 20-generator system is used for testing. A cascading line trip sequence is expected to be prevented immediately after the first grid component outage
