Unified Power Flow Controller (UPFC)

Unified Power Flow Controller (UPFC)

UPFC stands for Unified Power Flow Controller.UPFC can control both active and reactive power flows in transmission system.UPFC uses solid state devices.UPFC is a combination of STATCOM (shunt) and SSSC (series) coupled common voltage DC link.It was invented for real time control and dynamic compensation of AC transmission system.UPFC can control simultaneously or selectively voltage impedance phase angle in transmission line and hence it is called UNIFIED.UPFC is a generalized synchronous voltage source (SVS).

UPFC consists of two back to back voltage source converter operated by common dc link dc storage capacitor.The function of converter 1 is to supply or absorb real power demanded by converter 2.Converter 1 can be operated by unity power factor.Reactive power of converter 1 and converter 2 is independent of each other.Because no reactive power flow through dc link.The UPFC can operate only under balanced sine wave condition.