Switch time bifurcation elimination analysis in SVC plants

Studies show that switching angle of thyristor controlled reactor (TCR) in VAR compensator (SVC) plant, which is typically linked by a coupling transformer to the grid, misshapes current waveforms, which may lead to bifurcation and unsatisfactory operation of the station. A system model is developed by intelligent resistance method (IRM) method and used to access the impact of coupling transformer on occurrence of bifurcation phenomenon. Next, methods for eliminating the bifurcation problem by TCR control procedures are presented and compared. A modified switching method, capable of eliminating the switch time bifurcation phenomenon and allowing SVC to perform freely in all control zones is elaborated. By using this method, the fundamental component of SVC current will be improved and harmonics will be reduced to acceptable levels, which guarantees the proper operation of SVC plant.