Abstract: When a short circuit fault occurs in the power systems,the series converter of unified power flow controller（UPFC） may be damaged because of bearing high voltage and large current.A novel flexible AC transmission system（FACTS） device called unified power flow controller with fault current limiting（UPFC-FCL） is presented.It consists of a UPFC module and a FCL module connected via the series coupling transformer.The topology,working principles and control strategies of UPFC-FCL are discussed as well.In normal conditions,FCL module appears as "zero impedance" and UPFC-FCL is equivalent to a regular UPFC.When a short circuit fault occurs near the device in the power system,FCL module will transform from "zero impedance" into "large impedance" immediately and automatically limit the fault current.UPFC-FCL can not only protect the UPFC series converter from being destroyed by the high voltage and large fault current of the system but also lower the fault current level in the power system.PSCAD/EMTDC simulation results demonstrate the validity of the proposed device.