Active filtration method and device for simultaneously restraining difference mode interference and common mode interference

Abstract

The invention discloses an active filtration method and device for simultaneously restraining difference mode interference and common mode interference. The method comprises the following steps that (1) a plurality of active power filters are respectively bridged between each power supply bus and each neutral line, and meanwhile, a current sensor is arranged on each power supply bus, and each current sensor is respectively connected to the corresponding active power filter bridged between each power supply bus and each neutral line; (2) each current sensor monitors harmonic interference current on each power supply bus; and (3) each active power filter works based on a feedback control principle, so that the harmonic interference current on the power supply bus, which is monitored by each corresponding current sensor, is minimum, and meanwhile, the harmonic current of the neutral line is minimum. According to the active filtration method and device, through a connection way of two active power filters and the ground wire, a certain compensation harmonic current is injected into the power supply buses, and meanwhile, the difference mode interference and the common mode interference on the power supply buses are removed, and the low-frequency interference conduction and radiated emission quantity of the long distance transmission cable of the power grid can be effectively controlled.

Description

technical field [0001] The invention belongs to the field of electromagnetic compatibility, and in particular relates to an active filtering method and device for simultaneously suppressing differential common-mode harmonic interference. Background technique [0002] In the power transmission grid, in addition to outputting electric energy to the grid in differential mode, the generator will also output differential mode and common mode interference at the same time. The characteristic of differential mode interference is that the phases of the interference signals between the two power supply buses are opposite. Such interference signals cannot cancel each other inside the equipment, so it is the main reason for the interference of electrical equipment. The characteristic of common mode interference is that the phase of the interference signal between the two power supply buses is the same. It usually does not interfere with the equipment in a conductive manner. However, it...

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Problems solved by technology

[0011] (1) It is difficult to accurately control the distributed capacitance of the output bus of the generator set to the ground, and its AC harmonic interference energy exists in the form of differential mode and common mode at the same time, and the interference current coexists with the supply current of thousands of amperes. If the EMI passive filter is used scheme, it is difficult to manufacture passive devices such as resistors, coils, and capacitors that meet capacity requirements;

[0012] (2) In the frequency range of DC to 10kHz, if the common-mode interference energy is large, it is difficult for the common-mode choke coil to suppress the common-mode interference in this frequency range;

[0013] (3) The grid power supply cables and electrical equipment space requirements are strict, so the distance between the power supply cables and the signal cables of some sensitive equipment is too close or even bundled, and the coupling interference between cables caused by common mode radiation is serious. The threat of interference is caused, and the cost of uniformly adding EMI filters or changing the current cable layout at the electrical equipment is very high, and the effect is difficult to guarantee

[0026] It can be seen that this method is connected to the power active filter, which cannot effectively suppress the common-mode interference current, but can only change the amount of differential-mode interference. When the grid initially interferes with I cm >I dm , not only cannot suppress the interference, but even increase the differential mode interference

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