Representative imageActive Harmonic Filters
An active harmonic filter (AHF) is a shunt-connected IGBT PWM power converter that continuously measures load current, computes the harmonic and reactive components, and injects equal-and-opposite harmonic currents in real time to cancel distortion at the point of connection.
Overview
An active harmonic filter (AHF) is a shunt-connected IGBT PWM power converter that continuously measures load current, computes the harmonic and reactive components, and injects equal-and-opposite harmonic currents in real time to cancel distortion at the point of connection. Unlike a passive filter it adapts dynamically to changing loads, corrects multiple harmonic orders simultaneously, and can also deliver reactive-power / power-factor correction and load balancing. ACE's unit conditions current distortion in under 5 ms and drives system THDi below 10% (typically <5% at the PCC), eliminating neutral overloading and reducing I²R and transmission losses. Buyers select an AHF for installations with highly variable or mixed non-linear loads where guaranteed IEEE-519 compliance, near-unity power factor and future expandability matter more than first cost; rating is by harmonic compensation current (amps), so multiple modules can be paralleled.
Specifications
| Compensation current rating | typically 30 A to 150 A per module; parallel modules to several hundred / thousand amps |
|---|---|
| Voltage class | 208-415 V (up to 690 V), 3-phase 3-wire and 3-phase 4-wire (with neutral compensation), 50/60 Hz |
| Topology | IGBT PWM active front-end converter, DSP closed-loop control |
| Response time | full correction within < 5 ms; transient response in the tens of microseconds |
| THDi result | system THDi < 10%, commonly down to <5% per IEEE-519 |
| Harmonic orders corrected | selectable up to ~50th order |
| Functions | harmonic cancellation + reactive/PF correction (lead/lag) + load balancing |
| Mounting | wall-mounted, rack/cabinet, or floor-standing modular |
| Cooling | forced-air (fan-cooled); efficiency typically >97% |
| Applicable standards | IEEE-519, IEC 61000-3 / 61000-4 |
Applications
- Data centres and IT/UPS loads with mixed non-linear equipment
- Buildings/HVAC with many small VFDs and variable load
- Hospitals and commercial facilities requiring power-quality compliance
- Manufacturing plants with fluctuating drive and welding loads
- Neutral-current / I²R loss reduction in 3P4W distribution
- Power-factor and IEEE-519 compliance where passive filters cannot adapt
Frequently asked questions
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- System voltage & frequency
- Load rating (kVA / A)
- Existing or target THD / standard (e.g. IEEE-519)
- Source & load type (drives, rectifiers…)
- Enclosure & mounting
- Application / end-use
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