Active harmonic filters are parallel filters (which means the current doesn’t go through the filter) that are used to reduce, or mitigate, harmonics to tolerable levels as defined by IEEE-519. Active filters use a set of transistors and capacitors to filter (or clean) the current wave by injecting inverse currents to cancel out the undesired harmonic components. Active filters are significantly more expensive than passive filters and take up more space. Size is an immense factor in system design today and should be accounted for when deciding on what type of harmonic filter is right for you.
Active filters can work with multiple drives; when the active filter reaches its limit, it won’t overload. In addition, if an active filter breaks, it won’t stop the motor (since current isn’t going through the filter); it just won’t filter the current wave.
AHFs can take care of several other power quality problems by combining different functions in a single device:
⦿ Elimination of harmonic currents and voltages.
⦿ Power factor correction (lagging or leading).
⦿ Voltage variations (sags & swells) reduction.
⦿ Voltage fluctuations (flicker) mitigation.
⦿ Load balancing in three-phase systems.
⦿ Controlled & selectable harmonic generation.
An Active Harmonic Filter is a power electronics-based device connected in parallel with the load that requires harmonics mitigation. AHF works as a controlled current source providing any kind of current waveform in real time.
AHFs monitor the currents of the load and compensate any produced harmonic currents by generating a compensation current for each selected harmonic order in phase opposition to the harmonic current. Result is reduction on the levels of harmonics of the installation to the limit requested by the customer ensuring compliance with power quality standards and recommendations.
ZDDQ--excellent manufature of active harmonic filter/static var generator.
NO.25,JINHE RD,HUAIYUAN ECONOMIC DEVELOPMENT ZONE ,BENGBU,ANHUI
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