active power filter
Active Harmonic Filter
Jan 08, 2019

zddq power quality solutions application

Overview of Active Harmoinc Filter

Active Harmonic Filter(AHF) is a perfect comprehensive solution to power quality problems such as harmonic wave, reactive power, and 3 phase load unbalance. AHF is connected in parallel in power grid, to detect the harmonic wave in real time, generate the reverse-phase compensation current through the converter, and dynamically filter the harmonic wave. The operation of AHF is unaffected by power grid structure and load type, and it will not produce harmonic oscillation with the system, thus perfectly realizing harmonic wave control of various loads. AHF can also realize dynamic reactive compensation, and control the capacitor switching, to improve the power factor. Meanwhile, Active Harmonic Filter has the function of controlling the 3 phase load current unbalance, thus comprehensively solving various power quality problems with power grid.

Principle of Active Harmoinc Filter

single line diagram of active harmonic filter

Key Features of Active Harmonic Filter

  1. Multifunctional: Harmonic, reactive power and imbalance compensation
  2. High harmonic filtering rate: Up to 98%
  3. Excellent reactive compensation: High speed, Precise (-0.99≤PF≤0.99), Step-less, Bi-directional (capacitive and inductance) compensation
  4. Excellent imbalance correction: Both negative and zero sequence, mitigates neutral current
  5. Wide input voltage & frequency range, adapts to tough electrical environments
  6. Low thermal loss (≤3% of rated AHF kVA), efficiency ≥ 97%
  7. High stability: Infinite impedance to grid, avoids harmonic resonance problems
  8. Flexible application: Modular design, embedded in standard or customized cabinet
  9. Easy installation and maintenance: Plug-in installation for AHF module replacement and expansion
  10. Wide capacity range: 30A~600A for a single cabinet, up 10 cabinets in parallel
  11. Environmental adaptability: -10~50°C temperature, compatible with diesel generator
  12. Complete protection: Grid Over/Under voltage, AHF over current, over temperature, and more. All faults are recorded in the event log, which is convenient for failure analysis

Typical Application of Active Harmonic Filter

Harmonics occur usually as follows,

Overheating of transformers and conductors

Generator instability

Capacitor failure

Nuisance tripping of fuses and circuit breakers

Damage to or failure of sensitive electronic equipment including drive failure

Telephone interference

Motors experiencing overheating, audible noise and reduced service life

High energy costs

Downtime and loss of production due to equipment instability.

AHF Modular Datasheet

Number of phases (system input)

3-phase 3-wire or 3-phase 4-wire

Rated frequency


Rated voltage

400 V ±20%

Response time


Harmonic mitigation performance

2nd to 50th harmonic

Filter Efficiency


Total harmonic current distortion THDi


Reactive power compensation Rate

>0.98(inductive and capacitive compensation)

3 phase unbalance compensation effect


Active Loss of system


Inverter topology




Current transformer placement

Mains side or load side

Communication interface

Modbus Protocol,RS485

Rated current of Modular


50 A

75 A

100 A










Over heat protection


Over/under voltage protection


Over/under frequency protection


Noise level

<60 dB (depending on load situation)

Relative humidity

<95% non-condensing


-20 ~70°C

Cooling type

Air cooling

Dimensions cabinet

440 mm × 641 mm × 230.5mm (w × d × h)


Wall-mounted or Rack mounted

Ambient conditions

<1000m; Up to 4000m with derating 1% per 100m

Protection class



ISO9001,Type Test Report

EN 50178:1997/IEC50178:1997

Design standards



EN50091-3/IEC62040-3/AS62040-3(VFI SS 111)

ZDDQ Related Products

  1. Active Harmonic Filter Modular
  2. Active Harmonic Filter
  3. Static Var Generator
  4. Advanced static Var Generator
  6. Hybrid power factor correction with filter mitigation
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