Power Flow Control by Using DPFC

this paper presents a new component within the flexible ac-transmission system (FACTS) family, called distributed power-flow controller (DPFC). The DPFC is derived from the uni-fied power-flow controller (UPFC). The DPFC can be considered as a UPFC with an eliminated common dc link. The active power ex-change between the shunt and series converters, which is through the common dc link in the UPFC, is now through the transmis-sion lines at the thirdharmonic frequency. The DPFC employs the distributed FACTS (D-FACTS) concept, which is to use multi-ple small-size single-phase converters instead of the one large-size three-phase series converter in the UPFC. The large number of series converters provides redundancy, thereby increasing the sys-tem reliability. As the D-FACTS converters are single-phase and floating with respect to the ground, there is no high-voltage isolation required between the phases. Accordingly, the cost of the DPFC system is lower than the UPFC. The DPFC has the same control capability as the UPFC, which comprises the adjustment of the line impedance, the transmission angle, and the bus voltage. The principle and analysis of the DPFC are presented in this paper and the corresponding experimental results that are carried out on a scaled prototype are also shown.