The harmonics of the power supply system of rail transit (subway, high-speed rail, etc.) mainly come from the traction power supply system that supplies power to the vehicle. During train operation, harmonics and unbalanced currents will be generated due to power fluctuations, rectifier commutation, large load changes, train starting or braking, power supply arm switching, vehicle inverter, etc., which seriously affect the correct work of the relay protection device, and at the same time, it also affects the safety of transformers and rotating machines, and interferes with the normal communication of rail transit system. Harmonics have become a major threat to rail transit operations.
The power load of urban rail transit can be divided into two major power consumption groups according to its different functions:
1. The traction load required for the operation of electric buses;
2. Power lighting electricity required by stations, sections, depots, control centers and other buildings, such as: ventilators, air conditioners, escalators, elevators, pumps, lighting, AFC systems, FAS, BAS, communication systems, signal systems, etc.
The harmonic sources in the power supply system of urban rail transit are mainly as follows:
1. High-order harmonics generated by traction rectifier inverter device (11th, 13th, etc.);
2. A large number of nonlinear loads in station substations (3, 5, 7, etc.).
Rail transit harmonics mainly come from the rectifier and inverter devices of vehicle traction power supply, followed by DC power supply complete sets, lighting, elevators, display screens, air conditioning, drainage and other devices, mainly based on 5, 7, 11, 13 harmonics, but also contains some 3 harmonics. The reactive power reserve in the harmonic consumption system increases the line loss, affects the reliable operation of relay protection and automatic control devices, reduces the operational safety of the electrical equipment, and produces electromagnetic interference on communication and signals. Harmonics can also have a destructive effect on other reactive power compensation devices in the line, while the reactive power compensation device also amplifies harmonics, forming a vicious circle.
The existence of power quality problems has brought serious harm to the rail transit industry, for this reason, Bowo provides a complete set of solutions, as follows:
| No. | Power Quality Problem | Solution |
| 1 | Low power factor , high reactive power demand | BW-SVG BW-LC BW-TSVG BW-UPQC |
| 2 | Harmonic | BW-APF BW-TAPF BW-UPQC |
| 3 | Three-phase unbalance | BW-SPC |
Rail transit, especially subway power supply system, has very strict requirements for power supply reliability, and harmonics are the main cause that threatens its power supply reliability. The use of active filters can effectively control harmonics, reduce the damage of harmonics to the power supply system, and ensure the safe and stable operation of rail transit. At the same time, after the harmonic filtering is removed, the harmonic loss of the system is reduced, and the original capacitor compensation equipment can be used normally, further reducing the system loss.
1. Application of BW-APF active power filter in Shanghai metro
2. Application of BW-APF active power filter in Hangzhou metro
3. Application of BW-APF active power filter in Beijing metro
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