Research on the Source Tracing Method of Three-Phase Unbalance Based on Equivalent Circuit

The three-phase imbalance phenomenon of power system under normal operation has aroused the increasing concern of power supply and consumption departments, which will have a certain impact on the power quality of the grid. It is urgent to determine the source of imbalance in the complex distribution system, and then take appropriate governance measures to solve the problem of three-phase imbalance in power system. How to determine the location of the unbalanced disturbance source is particularly important for taking further control measures. However, the existing methods require that the power quality testing instrument used to measure the phase requires high accuracy and may cause error in judgment when the negative sequence current is less than a certain range of the measuring instrument. Therefore, following the modeling idea of harmonic source load equivalent circuit, this paper equates the unbalanced load as the parallel connection of negative sequence current source and impedance. By comparing the three-phase unbalanced voltage contribution level of the system side and load side at the measuring point, the location of the main three-phase unbalanced source can be distinguished. The method is simple and effective and has certain advantages in practical engineering applications.