SUPPRESSION OF NUMERICAL OSCILLATION CAUSED BY THE EMTP-TACS INTERFACE USING FILTER INTERPOSITION

Transient phenomena of power system and the control system are simulat ed in EMTP (Electromagnetic Transients Program) and TAGS (Transient An alysis of Control Systems) respectively. The internal variables are tr ansmitted between two routines, and numerical solutions are done separ ately at each time step. This implies time delays exist in EMTP-TACS i nterface. These may cause undesirable effects such as numerical instab ilities and incorrect results. In this paper, both the power system pa rt inside the EMTP and the control system part inside the TAGS are reg arded as a feedback system from the viewpoint of system stability, the characteristics of these interface delays are clarified, and a method to suppress numerical oscillations based upon filtering is proposed. This method is simple and imposes no restrictions with respect to prac tical use.