Study of power system harmonics in an unbalanced system using the three-phase bus impedance matrix

Abstract

The authors study the effect of harmonic current injected at a certain bus on the voltages at the other buses using the three-phase bus impedance matrix of an unbalanced system at normal and abnormal conditions. The effects of the system capacitors (grounded or ungrounded) in the presence of harmonic distortion is also studied. The results show that for both normal and abnormal system conditions, the highest voltage variations occur when the system capacitors are disconnected. The best case (smallest voltage variation) occurs when the system capacitors are grounded. In the case of ungrounded capacitors, the voltage variation falls in between the other two cases. These conclusions apply to higher harmonic orders. It is also found that the buses closest to the source of injected harmonic current are subject to extremely high voltage variation.<>