Transient Characteristics of a UPFC, and its Effect on Suppressing Power Flow Variation

This paper describes transient characteristics of a UPFC and its performance of suppressing power flow variation in a power transmission system having two parallel lines. The UPFC is installed in series with the two parallel lines and it controls the total power flow of the lines. Dynamic performance caused by a single line trip is theoretically and experimentally discussed. Experimental results tells us that a conventional control may produce an excessive power flow variation at the instant of the trip. On the other hand, fast control scheme which has been proposed by the authors shows good performance of power flow control without any variation not only in steady state but also in transient state.