Unified Power Flow Controller

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A Unified Power Flow Controller (or UPFC) is an electrical device for providing fast-acting reactive power compensation on high-voltage electricity transmission networks. It uses a pair of three-phase controllable bridges to produce current that is injected into a transmission line using a series transformer. The controller can control active and reactive power flows in a transmission line. The UPFC uses solid state devices, which provide functional flexibility, generally not attainable by conventional thyristor controlled systems. The UPFC is a combination of a static synchronous compensator (STATCOM) and a static synchronous series compensator (SSSC) coupled via a common DC voltage link. The UPFC concept was described in 1995 by L. Gyugyi of Westinghouse. [1] The UPFC allows a secondary but important function such as stability control to suppress power system oscillations improving the transient stability of power system.


  1. ^ Gyugyi, L.; Schauder, C.D.; Williams, S.L.; Rietman, T.R.; Torgerson, D.R.; Edris, A. (1995). "The unified power flow controller: A new approach to power transmission control". IEEE Transactions on Power Delivery 10 (2): 1085. doi:10.1109/61.400878.