A Novel Concept for Stabilization of AC/DC Network with UPFC

This paper presents a novel concept for stabilization of AC/DC network with Unified Power Flow Controller (UPFC). The system considered has the structure of two areas connected by HVDC link. The investigation for perturbation in ac bus voltages has been carried out and the effect on the stability deterioration has been analyzed. The new concept of control has been proposed by embedding UPFC and then generating the control decisions adequately which stabilizes the earlier one. The concept of including the Unified Power Flow Controller (UPFC) in AC/DC network especially where a DC link is embedded to connect the two AC Systems is proposed. The proposed control design has been done utilizing a Novel Discrete–Time model of AC/DC system. The complete system stability has been studied in which the individual controller such as HVDC-SVC and HVDC-SVC-UPFC performance under varying perturbation of ac system voltage has been widely analyzed. The results show that in situations the HVDC-SVC alone is unable to reject the perturbation, the UPFC along with the HVDC – SVC damps the oscillations, thus matching the real and reactive power demands adequately. This novel combination can effectively be utilized in situations when the ac system bus voltage undergoes the fluctuations due to changing P and Q requirements.