Methods For Voltage Sag Source Location Based On The Sequence Component Of Disturbances

Voltage sag has become the most important dynamic power quality problems.Only after information about a disturbance location is available, can diagnosis andmitigation strategy be carried out. Moreover, any disputes can be resolved fairly.Voltage sag location is to determine the disturbance origins’ relative position tomonitoring device. Existing methods do not work well for asymmetrical sags.Four basic methods of existing voltage sag source location methods aredescribed in detail in this paper. Theoretical analysis, location step, advantages anddisadvantages about each method are introduced, and the existing methods can beclassified into two types which are based on energy and impendence methods. Themethod of disturbance power and disturbance energy, investigating slope of thesystem trajectory, current real component polarity and real part of the equivalentimpedance are tested in the two-source model. Simulation results show that theirlocation performance is not ideal. The deficiencies of these methods are deeplyanalyzed in this paper.Secondly, by analyzing power system faults, which is the main reason resultingin the voltage sags, two new location methods using disturbance power anddisturbance sequence power are proposed in this paper based on the superpositionprinciple of linear circuits. The disturbance sequence power method can solve theproblem which the disturbance power method can not locate short time sag. Thealgorithm of disturbance variables and the corresponding location criterion are shownin the paper. The methods are verified by simulation on the two-source system andIEEE9nodes model. The results obtained show that the proposed methods have ahigh effectiveness in voltage sag location caused by all kinds of faults. In particular,they act well for asymmetric dips. At the same time, the new methods can be used toany power grid structure (radial type, ring type, single-loop, double loop, one-source,and two-source), and is also suitable for locating other disturbance sources (eg:capacitor switching, transformer switching, large motor starting, etc.). Compared withexisting methods, the proposed method has a great advantage in theory andpositioning accuracy.