Effect of fault current limiting of UPFC for power flow control in loop transmission

The flexible AC transmission system (FACTS) is a power electronic-based technology used to enhance controllability and increase transmission capability under various electric power system conditions. Unified power flow controllers (UPFC), which are one type of FACTS, are proposed for many applications (power flow control, power swing damping, voltage dips compensation, fault current limiting, etc.). This paper focuses on UPFC introduced for power flow control, proposes a control system for DC voltage damping and fault current limiting, and discusses the contraction of range of instantaneous voltage drop by fault current limiting during power system faults.