The “cleanup crew” role of wall-mounted active filters in traction power supply systems

Harmonic pollution is currently the most pressing issue in traction power supply systems for subways and high-speed railways, much like “junk food” in the power grid. Wall-mounted active filters (AHF) act as intelligent cleaners, specifically designed to detect and eliminate these harmonics.

Its operating principle is ingenious: by continuously monitoring current waveforms, it immediately generates opposing currents to cancel out any harmonics that exceed the threshold. It works like a noise canceller—the louder you shout, the stronger the opposing sound waves it emits to neutralize the noise. Installing a few wall-mounted units in a traction substation can quickly eliminate the characteristic 5th and 7th harmonics generated by rectifier units.

There are three major advantages of Wall-mounted active filters (AHF)  in practical applications: first, the wall-mounted design does not occupy floor space, making it particularly suitable for traction substations where space is at a premium; second, it has a fast dynamic response, acting in milliseconds, which is much more flexible than passive filters; third, it has a built-in smart chip that can learn and record harmonic change patterns, becoming more accurate with use. This equipment is now standard on newly built subway lines, and older lines are being retrofitted with it.

However, it is important to calculate the harmonic mitigation capacity carefully during selection, avoiding the temptation to opt for larger or more expensive models. It is generally recommended to leave a 20% margin, as harmonics can surge suddenly during train acceleration compared to steady-state operation. Maintenance is straightforward, requiring only regular dust removal, making it far simpler than car maintenance.

Looking for the best solutions to improve power quality? Our 500V Wall-mounted Active Harmonic Filter offers efficient performance and reliable protection. Discover how GEYA's innovative solutions can meet your needs. Contact us for more information! As a professional manufacturer and supplier, we provide high-quality products. If you are interested in our products or have any questions, please feel free to contact us.