A novel steady-state model and principles of operation of phase-shifting transformer comparable with FACTS new devices

Phase shifters are used in power systems to control the power flow. The classical model of phase shifter is presented by unsymmetrical elements arranged in π configuration. This model is not conceptually adequate to express its behavior. The unsymmetry in this model puts the load flow program in trouble; most load flow programs use the advantage of the symmetrical matrix in their algorithm. In addition, by introducing the new FACTS devices which are based on voltage source converter (VSC) technology, it is necessary to reconsider the classical model in order to compare its behavior with the new devices. In this paper, the model developed for phase shifters is symmetrical and general without any approximation. From the circuit viewpoint, this model is more suitable to be compared with new FACTS devices. Finally, based on this model, the merits and limits of phase shifters are evaluated and their behavior is compared with the unified power flow controller.