Control design and analysis of UPFC shunt converter

A unified power flow controller (UPFC) has the potential of controlling transmission line real power, reactive power and node voltage. It is one of the most promising FACTS devices. In this paper operation principle and model of UPFC are introduced, and a novel double PI decouple control strategy is proposed. A current feed-forward control is introduced into current inner loop of dc-link capacitor voltage control system and node voltage outer loop control system adopt voltage droop control which consists of PI regulation and scaling factors of droop characteristic. Design proceeding of controller parameter is discussed in detail and simulation model in Matlab6.5 is established. The simulation results for a case study indicate that dc-link capacitor voltage and node voltage can be controlled efficiently, attest that control scheme and controller design are viable and effective. This paper settles foundation in both practice and theory for further manufacturing UPFC laboratory-scale equipment