Application background:

　　The harmonic sources of urban subway traffic can be divided into two major electrical equipment:

　　1) The high-order harmonics generated by the high-voltage 35KV side traction rectifier inverter device, the dominant harmonics are 11th, 13th, 23rd and 25th;

　　2) Low-order harmonics produced by variable frequency fans, central air conditioners, variable frequency elevators, electronic rectifier energy-saving lamps, advertising boxes, UPS, etc., which are widely used in low-voltage 0.4KV side stations, sections, depots, control centers, etc., dominate harmonics5 Times, 7 times, 11 times.

　　The natural power factor of the low-voltage side is low, and the reactive power fluctuates greatly when working at full load during the day;

　　3) The natural power factor of the high-voltage side is relatively high. Due to the long power supply line, there is a phenomenon of reactive power reverse transmission at night when the load is light;

　　Recommended plan:

　　The low-voltage 0.4KV side is directly used for centralized management by DVG digital reactive power generators, and the high-voltage 35KV side is directly connected to the bus below 35KV through the step-up transformer with APF active filter to filter out high-order harmonics and adjust the power factor in both directions. Prevent reactive power backwards.

　　Design capacity of active filter = operating current * current distortion rate

　　Note: In order to make the compensation effect better, there is generally a margin. Therefore, the effective harmonic current under the maximum load rate is generally calculated by multiplying 1.2 as the final configuration capacity.

　　Customer benefits:

　　Reduce the harmonic content to ensure the safe and stable operation of the subway power supply system;

　　The safety improvement of the power factor can avoid the fines caused by reactive power backward transmission;

　　Energy saving and consumption reduction, reducing rail transit operating costs.