  Unified Power Flow Controller (UPFC) is recognized as the most powerful
flexible AC transmission systems (FACTS) device for power system operation.
This paper addresses how UPFC explores the transmission flexibility and
facilitates the integration of uncertain and volatile wind power generation. To
this end, a comprehensive unit commitment (UC) model with UPFC and uncertain
wind power generation is proposed. Then, some metrics are introduced to
evaluate the impacts of UPFC on the reliability, security and economy of power
system operation. Further, different dispatch strategies of UPFC are compared
to provide helpful guidances on making full use of UPFC to hedge against
uncertainties. In addition, facing the challenging mixed-integer non-linear
non-convex problems, approximate models are proposed to provide a starting
point to solve the problems efficiently. All these models are easy to adapt to
other types of FACTS devices. Illustrative numerical results are provided.
