Abstract:With the development of distribution network and the wide access of power load, the unbalanced three-phase load problem of distribution transformers is becoming more and more serious. In this paper, the active three-phase unbalanced compensation device is applied to the distribution area. Firstly, problems brought by the unbalanced three-phase load is pointed out. Meanwhile the principle of power quality improvement and loss reduction of the distribution area is analyzed. Secondly, actual distribution transformer, line and load conditions are simulated based on the "power grid energy saving and loss reduction technology laboratory". Experiment results verify that the device can compensate reactive power while adjusting the load imbalance. Two key factors that affect the loss reduction effect of the device are obtained through the variable control method: the length of the power line between the device access point and the transformer and the efficiency of the device itself. Furthermore technical improvement of the active compensation device is put forward. Finally, two devices have been installed in the power supply bureau of Guiyang. The operation of the active compensation device verifies the correctness of the theoretical analysis and experimental results.