Unified Power Flow Controller And Its Effects On Relay Protection

As an important application of FACTS, unified power flow controller (UPFC) ismulti-function device which is based on the power electronic technology developedin 1980s. UPFC can be serviced as phase shifter, SSSC and reactive power generatorwhich can be used to regulate the voltage level and compensate the reactive power ofpower system. However, the introduction of UPFC also brings some new problems toother equipments in the system, especially to the relay protection. This paper mainlymade a research on UPFC and its effects on protection system, especially on thedistance protections. This paper also researches the UPFC model itself, finding thereason of harmonic production of UPFC, and points out the basic control strategies;the effects of UPFC on line protection system also were analyzed under symmetricand non-symmetric conditions. Under the base of main control configuration, theinfluence of UPFC on protection is simulated by using of PSCAD/EMTDC. Theperformance of a distance relay has been evaluated and some adaptive schemes havebeen proposed. Results of simulation with EMTDC/PSCAD are given.