C-UPFC: a new FACTS controller with 4 degrees of freedom

FACTS controllers based on voltage-source converters have inherent voltage support so that they can be sited roughly halfway in the middle of the radial transmission line, where they are more effective since the length of the line becomes virtually shorter by half and the transmissibility of power is doubled. The center-node unified power flow controller or C-UPFC has been conceived for mid-point siting and is provided with 4 control degrees of freedom which are used to control: (1) the real power through the line, (2) (3) the reactive powers at both ends of the line and (4) the magnitude of the AC voltage at the mid-point. The C-UPFC has two series converters and one shunt converter. The real AC power which is rectified by one series converter emerges as inverted power by the other series converter via their DC link. The shunt converter operates exclusively as a STATCOM