HF
Single-tuned harmonic filter
A shunt series-LC branch tuned near one harmonic order to sink that harmonic current from the network.
SLD / Schematic
Symbols · AHF
Active harmonic filter
A shunt converter that measures load harmonics and injects opposing currents to cancel them at the connection point.
In plain English
What does Active harmonic filter mean?
An active harmonic filter is a shunt-connected voltage-source converter that measures load current through current transformers, calculates the harmonic content and injects equal and opposite currents. It can also correct power factor and balance load between phases. Response adapts to changing loads, so it does not need tuning to particular orders.
A simple example
Single-line diagrams show a converter block with a wave or harmonic mark, connected to the switchboard bus through a breaker, with current transformers on the load side or on the supply side depending on the control method. Several modules are often paralleled.
What the drawings help you do
The filter rating is in amperes of compensation current, not in kvar, and it can only cancel harmonics within that current and frequency range. The symbol does not tell you where the current transformers are, which decides whether the filter compensates the whole board or one load.
This particular reference
A shunt converter that measures load harmonics and injects opposing currents to cancel them at the connection point. An active filter cancels harmonics with a converter; a passive filter sinks them with tuned capacitors and reactors.
- Winding
- A coil of conductor inside an electrical machine or transformer.
- Phase
- One of the related AC waveforms in a power system.
- Rating
- A value stating the conditions for which equipment is specified.
Read the source: STATCOM: converter-based reactive power compensation · IEC graphical symbols for diagrams
SLD / Schematic · AHF
What it represents
An active harmonic filter is a shunt-connected voltage-source converter that measures load current through current transformers, calculates the harmonic content and injects equal and opposite currents. It can also correct power factor and balance load between phases. Response adapts to changing loads, so it does not need tuning to particular orders.
Single-line diagrams show a converter block with a wave or harmonic mark, connected to the switchboard bus through a breaker, with current transformers on the load side or on the supply side depending on the control method. Several modules are often paralleled.
The filter rating is in amperes of compensation current, not in kvar, and it can only cancel harmonics within that current and frequency range. The symbol does not tell you where the current transformers are, which decides whether the filter compensates the whole board or one load.
How to read it
- Find the current transformers; their position defines what is being compensated.
- Ratings are given in compensating amperes.
Information to show or reference
- State compensating current and harmonic range.
- Show current transformer location.
- Reference parallel module arrangement.
A distinction that matters
An active filter cancels harmonics with a converter; a passive filter sinks them with tuned capacitors and reactors.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
STATCOM: converter-based reactive power compensation
Public converter-based compensator page noting active filtering capability.
IEC graphical symbols for diagrams
IEC graphical symbol context for converters.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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