Full-color LED display requires low-voltage DC drive, so in the LED large-screen production engineering, a large number of switching power supply for the LED display module to provide the drive. In order to reduce the loss of low-voltage DC current in various transmission links, LED display screens generally use a large number of low-power switching power supply modules to configure a distributed local low-voltage DC power supply mode. This realization method solves the problem of low-voltage transmission loss, but it brings problems such as harmonic pollution and excessive midline current. The reasons for this problem are:
The switching power supply is the most typical harmonic source, and its harmonic content is very high. Its waveform is an intermittent spike. Since the generally used switching power supply has a small capacity (a typical case is the power supply of a laptop), it has not attracted enough attention from people. However, if a large number of switching power supplies operate at the same time, harmonics generated by them will not be ignored. If they are not handled, they may cause pollution to the power supply network and cause unpredictable damage to other equipment in the same power grid.
For a conventional three-phase balanced load, the normal current of the neutral line is generally less than 30% of the phase current. The full-color LED display system no matter how to configure the load distribution, but due to changes in the display screen, it will still bring instantaneous three-phase imbalance. Coupled with the influence of harmonic currents, the zero line current can reach 280% of the phase current.
Above reference only
The switching power supply is the most typical harmonic source, and its harmonic content is very high. Its waveform is an intermittent spike. Since the generally used switching power supply has a small capacity (a typical case is the power supply of a laptop), it has not attracted enough attention from people. However, if a large number of switching power supplies operate at the same time, harmonics generated by them will not be ignored. If they are not handled, they may cause pollution to the power supply network and cause unpredictable damage to other equipment in the same power grid.
For a conventional three-phase balanced load, the normal current of the neutral line is generally less than 30% of the phase current. The full-color LED display system no matter how to configure the load distribution, but due to changes in the display screen, it will still bring instantaneous three-phase imbalance. Coupled with the influence of harmonic currents, the zero line current can reach 280% of the phase current.
Above reference only
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