Modeling and control of C-UPFC for power system transient studies

This paper presents the transient model of a new FACTS device, the center node unified power flow controller (C-UPFC), installed at the midpoint of a transmission line. The C-UPFC consists of three voltage source inverters (VSI) with common DC link. One of the converters is connected in parallel at the midpoint of line and the other two converters are connected in series. The simulation results indicate that the C-UPFC is capable of independently controlling the active and reactive power flows at the both ends of line and the magnitude of AC voltage at line mid point. It is shown that by adding a supplementary control system to the shunt inverter control system, it is possible to balance line current too.