The main loads of the power distribution system in the rail transit industry include ventilation motors, air conditioners, boarding and alighting elevators, water pumps, lighting systems, communication systems, signal systems, fire protection systems, office systems, monitoring systems, etc. The load harmonic distortion rate of the distribution system of urban rail transit is generally 25% ~ 30%, and the 3rd, 5th, 7th, 11th and 13th harmonic currents are the most serious. In the past, active power filters installed on site were mainly connected in parallel by module units with capacities of 50A, 60A and 100A (mostly one module). The multi-redundant hot-plugging scheme recommended by our company is composed of 25A, 30A and 35A hot-plugging modules, which realizes that multiple modules in a single set of active power filter devices are on standby for each other and maintenance-free behind the cabinet.

Photos of Traditional Active Power Filter Cabinet and Multi-redundant Hot-plugging Complete Machine

Case: Ningbo Metro Line 4 Multi-redundancy Hot-plugging Filter Project and Ningbo Metro Line 5 Multi-redundancy Hot-plugging Filter Project.

The rail transit industry gradually popularizes the local management scheme of MAC hot-plugging modules in the frequency converter cabinet. In this type of scheme, the MAC active filter module is installed in the frequency converter cabinet to comprehensively adjust and compensate the harmonic current and reactive power of the frequency converter. This scheme effectively replaces the passive filter module at the original frequency converter port, avoids the risk of resonance, and perfectly realizes the EMC electromagnetic compatibility problem at the input end of the frequency converter. Local or branch compensation also fully embodies the power quality concept of local control of harmonic sources, which is worth popularizing in various industries.

    Cases: In-situ Treatment Project of Frequency Converters for Qingdao Metro Line 8 and Nanchang Metro Line 3