ATC Enhancement Considering Transient Stability Based on Optimal Power Flow Control by UPFC

With recent development of power electronics technology, power system stability enhancement and optimal power flow control by using flexible AC transmission system (FACTS) devices have so far been studied. The FACTS devices to relieve multiple constraints can also make it possible to enhance Available Transfer Capability (ATC) without construction of new transmission lines. In this paper, a new method for improving transient stability by unified power flow controller (UPFC) is proposed. Then the proposed method is applied to an OPF control by using UPFC for avoiding multiple constraints. The new OPF method is used for enhancement of ATC taking into account transient stability constraints as well as overload and steady-state stability constraints. The OPF problem is formulated to minimize total inverter capacity of UPFC. Effectiveness of the proposed method is shown by numerical examples for 3-machine 9-bus system and 10-machine 47-bus system.