This project uses parallel capacitors for reactive power compensation. There are three common methods of high-voltage centralized compensation, separate on-site compensation and low-voltage centralized compensation. This design uses low-voltage centralized compensation. Low-voltage centralized compensation refers to the installation of low-voltage capacitors on a 0.4V low-voltage bus of a 10kV substation. Compared with other methods, low-voltage centralized compensation has the advantages of simple wiring, convenient operation and maintenance, high utilization of capacitors, and high economic efficiency. It is one of the commonly used methods in reactive power compensation. The parallel capacitor control method adopts automatic adjustment method, commonly known as reactive power automatic compensation device. The schematic diagram of the principle circuit of the low-voltage reactive power automatic compensation device is shown in Figure 1.