Abstract
In a three-phase nonlinear circuit composed of nonlinear reactors and capacitors, there are two noteworthy phenomena. One is the voltage jump phenomenon, which is very useful, and has already been used in the field of power devices such as frequency triplers. The other is abnormal voltage oscillation, which is very harmful to stable operation. In this paper, the mechanism and regions of occurrence of these abnormal oscillations are analyzed in detail.
It has been reported that voltage jumps in the three-phase nonlinear circuit can be analyzed by using only the zero-phase-sequence circuit equation. But positive- and negative-phase-sequence circuit equations are indispensable for analyzing abnormal oscillations. According to this analysis, it is shown that the resistances in the positive- and negative-phase-sequence circuits play the main role in these abnormal oscillations. It is also shown that there are two regions where the abnormal oscillations occur: the pre-jump region and post-jump region, and the fact that the former region occurs in the reactors' almost linear operating mode is particularly noteworthy.
