Control interactions between the HVDC and UPFC by use of the RGA

High Voltage Direct Current (HVDC) for power transmission and Unified Power Flow Controller (UPFC) for power flow regulation are important elements in a modern AC/DC power system. HVDC technology has been applied in real power systems for decades due to its distinct advantages in the aspect of long-distance and large-capability power transmission. While applications of the UPFC is still limited and potential problems of its implementation in real power system have not been investigated extensively and reported from the engineering practice. This paper reviewed the study of the dynamic interactions on HVDC and UPFC. Firstly in the paper, HVDC and UPFC technology is briefly reviewed and potential problem on their interactions is introduced. Secondly, two main methods of normal form and relative gain analysis (RGA) were introduced for the study of dynamic interactions. Finally, the paper summarized the existing research results and proposed further research directions that studying interactions between the HVDC and UPFC control functions by using the method of RGA.