For the urban metro rail transit system, the total extended length of railway lines is 10,811 km, of which 8,727 km are under the administration of national railways; the operational mileage reaches 4,928 km, including 3,358 km operated by national railways (covering 153 km of temporary operational lines) and 1,570 km operated by joint-venture companies. The operational mileage exceeded 7,060 km in 2010.
The operation of metro rail transit is characterized by sharp and random fluctuations. Meanwhile, its traction locomotives generate a large amount of harmonic currents during operation, which are directly injected into the power supply system, causing distortion of the power supply voltage waveform. This impairs the power supply quality of the traction power feeding system and may even affect the normal operation of the metro rail transit.
Figure 1: Urban Metro Rail Transit
The recommended solution is to install one set of MaxSine Active Harmonic Filter and one set of NCSD Tuned Filter; the active harmonic filter adopts the selective harmonic elimination mode to mitigate the 3rd, 5th, and 7th harmonic currents of the system, while the tuned filter is used to compensate the system power factor.
Key Features of MaxSine Active Harmonic Filter
- Filters out system harmonics, suitable for various harmonic environments with no overload issues
- Fast dynamic compensation response time ≤ 20 ms
- Multiple harmonic filtering modes and compensation functions available
- High-reliability IGBT protection architecture with excellent stability
Figure 2: MaxSine Active Harmonic Filter
Key Features of NCSD Tuned Filter
- Compensates the system power factor
- Can effectively prevent the occurrence of system harmonic resonance
- Equipped with an automatic power factor controller, which allows stepwise switching and outputs reactive power according to the system's demand
Figure 3: NCSD 270 Tuned Filter
滤波器于2009年8月28日投运迄今，投运后改善系统之电能质量与功率因数，于系统主回路改善前后之电能质量量测数据，如表1所示。
表1 系统改善前后之效果汇整表
图4 改善前系统电压与电流波形
图5 改善后系统电压与电流波形
图6 改善前后总谐波电流失真率历时图