Active Harmonic Filter (AHF)

Active Harmonic Filter (AHF)

Active harmonic filters (AHF) are the ultimate answer to power quality problems caused by waveform distortions, low power factor, voltage variations, voltage fluctuations and load unbalance for a wide range of segments and applications. They are a high performance, compact, flexible, modular and cost-effective type of active power filters (APF) that provide an instantaneous and effective response to power quality problems in low or high voltage electric power systems. They enable longer equipment lifetime, higher process reliability, improved power system capacity and stability, and reduced energy losses, complying with most demanding power quality standards and grid codes.

A2 Series

AHF Module Rate 400 V 50/60 Hz

Merus A2-series active harmonic filters deliver a real time response to mitigate harmonics up to 50th order enabling compliance with global power quality standards. In addition to active harmonic filtering, Merus A2-series active filters can also be used for voltage stabilization, power factor improvement, flicker mitigation and load balancing applications.


Merus™ A2-Active Harmonic Filters operate similarly to noise-canceling headphones. They measure the distorted current of the non-linear load and inject harmonic frequencies, but with an opposite phase angle. Canceling out harmonic currents reduces voltage harmonics and eliminates distortion at the point of common coupling.


Performance and scalable solution

Merus™ A2 performance is usually over 90% when compensating for 6-pulse drives, and it can keep the THDi under the required limits. We have optimized our active harmonic filter to work with typical variable frequency drives. By operating parallel to the VFD, Merus™ A2 keeps the feeder power quality in range. With the use of Merus™ A2 there is no need to worry about changes in the electrical network, as it is a dynamic solution. Merus™ A2 is easily integrate to operate with any VFD.

Load balancing and fast response time

Typically, any passive solution is too slow and cannot mitigate faster loads due to its response time. With a fast Merus™ A2 module, the voltage flicker, unbalance and harmonics can be mitigated in real time without worrying about the changes in the factory.

4W and proven product

With Merus™ A2, you can also cancel neutral harmonics with the same device. Merus™ A2 allows the electrical network to work better, avoiding costly issues in critical applications such as hospitals and data centers.

Medium voltage connectivity

Merus Power has a container solution for medium voltage installations, which can be fully tailored to customers' needs. Merus™ A2 medium voltage systems have been installed in multiple locations around the world and ensured renewable power grid connections.


3-level IGBT topology and design ensures:
  • High performance
  • Low heat losses
  • Low noise
Easy to integrate:
  • Integration for electrical cabinets
  • Maintenance possibilities
  • No external power supplies or controllers required
Capable to produce the nominal current at a typical harmonic spectrum
2 x ETHERNET + Modbus TCP
Smart features:
  • Linear derating on temperature
  • Automatic start and acknowledge
  • Stand-by feature for power saving
Merus™ A2 is a proven product:
  • Robust solution with long lifespan
  • No master-slave topology issues
  • High redundancy
One unit for:
  • 3W/4W
  • 50/60Hz
  • Voltage levels (200…480 and 480…690)
Preprogrammed digital input and outputs for hardwired signals
Multiple modules in parallel
  • Both open & closed loop CT configurationsUL508 and CSA rated modules

Typical segments

AHFs can be applied to small, medium or large appication in a wide range of segments.

Typical applications

AHFs have many low and high voltage potential applications where their use offers many benefits.
• Equipment using variable speed drives (VSD).
• Arcing devices: Electric arc furnaces (EAF), ladle furnaces (LF) and arc welders.
• Switch mode power supplies: Computers, TVs, photocopiers, printers, air cons, PLCs, etc.
• Battery chargers (incl. EV charging stations).
• Off-line, on-line & line-interactive UPS systems.
• Medical devices: MRI scanners, CT scanners, X-rays machines and linear accelerators.
• Lighting devices: LED, fluorescent, mercury vapor, sodium vapor & ultraviolet (UV) lamps.
• Solar inverters and wind turbine generators.
• Modulated phase controllers, cycloconverters and thyristor-controlled AC voltage regulators.
• Saturable/rotating devices: Induction heaters, transformers, generators, reactors and motors.
• Energy efficiency and savings: Lower energy losses and a higher efficiency of the system.
• Reduced production or installation downtime.
• Increased lifetime of electrical equipment.
• Better use of transformers and generators.
• Can take care of individual disturbance patterns and automatically adapt to changing load conditions and network topologies.
• Compliance with the strictest power quality standards and grid codes including G5/4, IEEE 519, IEC 61000 3-2/3-4 and EN 50160.

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