rail transit
the rail transit traction power supply system uses rectifier units to provide dc power to electric multiple units, so harmonics are inevitable. when the harmonic content exceeds a certain range, it may cause harm to the urban power system. in addition, lighting, UPS， loads such as elevators mainly generate harmonics of the 3rd, 5th, 7th, 11th, and 13th harmonics. and the load power is large, and the reactive power is also large.
harmonics cause the relay protection and automatic devices of the power system to malfunction or refuse to operate, directly endangering the safe operation of the power grid; they cause additional losses and heat in various electrical equipment, cause mechanical vibration and noise in motors, and harmonic currents in as a kind of energy flowing in the power grid, it will eventually be consumed on lines and various electrical equipment, thereby increasing losses. excessive reactive power and harmonics will cause increased losses and reduced efficiency of the transformer, and will be coupled to the high-voltage side, causing larger area of power quality issues.
lighting equipment, UPS， fans and elevators generate harmonic currents, causing voltage distortion. at the same time, the harmonic currents will be coupled to the high-voltage side through the transformer. after installing an active filter, the filter emits harmonics equal to the load and in the opposite direction into the power grid, harmonizing with the load. wave cancellation achieves the purpose of filtering and purifying the power grid, which can effectively reduce the failure rate of equipment. active filters have better performance than traditional passive filters, can dynamically compensate for harmonics, and are less prone to resonance.
scheme diagram reference
