Active harmonic filter

A Harmonic Filter as a solution for harmonic pollution

Reducing risks and ensuring safety

An Active Harmonic Filter can be applied as a solution to several Power Quality problems. One of the most common applications is to reduce harmonic pollution within electrical installations. An Active Filter provides “clean power”. Reduction of harmonic currents and contamination significantly reduces the likelihood of faults and problems. An additional advantage is that an Active Harmonic Filter reduces the absorption of reactive power and achieves a longer service life. This results in cost savings.

Actief Harmonisch Filter

Benefits of installing an Active Harmonic Filter

Prevention of breakdown and equipment failure
Maximum utilization of installation capacity
Improvement of energy efficiency
Securement of reliability and continuity
Reduction of service and maintenance costs
Prevention/reduction of unnecessary energy losses
Increased safety by reducing fire risk
Can be set to compensate for current imbalance between phases, minimising voltage imbalance


The emergence of non-linear loads, such as power electronics, has increased the demand and need for Active Harmonic Filters in most networks. In addition, an Active Harmonic Filter is still used as a suitable solution for very specific situations. Think of large power installations, such as installations with electric arc furnaces, induction furnaces and/or welding equipment. In many of these installations and in the presence of many non-linear loads, harmonic pollution occurs to a greater or lesser extent. To prevent problems such as malfunctions, equipment failure and sometimes even fire, it is necessary to reduce harmonic currents. An Active Harmonic Filter is a good solution for this.

Toepassing Actief Harmonisch Filter

What causes harmonic pollution?

Harmonic pollution is the result of harmonics in electricity. These harmonics are caused by non-linear loads in the network. One example of a non-linear load would be a LED lamp. Depending on the strength of the network (network impedance) and the magnitude of the harmonic currents, the voltage will distort and voltage quality will deteriorate. As a result connected equipment may malfunction or fail. In addition, the harmonic currents may overload the equipment and cables, resulting in (energy) losses and unnecessary heating of cables and components. A worst-case scenario could be temperature buildup resulting in a fire.

The Active Harmonic Filter reduces risks by reducing harmonics.

Curious about the possibilities?

We are happy to help you gain insight into the quality of electrical power within your installation. Through measurements, analysis and appropriate reporting, we offer you insight into the Power Quality status of your installation.

A maximum of 5% harmonic pollution

Harmonic pollution is a threat to operational reliability, energy efficiency and safety of electrical installations. Therefore, it is important to ensure the total harmonic pollution does not exceed a level of 8%, as prescribed by the Netcode (NEN-EN 50160). In specific situations HyTEPS recommends a maximum of 5%. In weak networks such as offshore installations, for example, or in critical sectors such as data centers and hospitals.

By installing a correctly dimensioned Active Harmonic Filter, you can reduce harmonic pollution and all associated risks.

THDU grafiek EN

The functioning of an Active Harmonic Filter

An Active Harmonic Filter is used to improve Power Quality through autonomous detection and dynamic filtering of harmonic currents present in the installation. The Active Harmonic Filter can detect any harmonic current flowing through the installation and counteract these. Detection of harmonic currents can take place on the power supply to a single harmonics- inducing load, or it can detect harmonic currents in the power supply of the total electrical installation.

On the power supply of a single load, the filter can focus all its capacity on this particular load and make sure that the harmonics induced by this device are countered before they can access other parts of the installation. This is very useful in situations where a large part of the harmonic pollution is created by a single device or device group on a sub-distribution board.

If a filter is placed on the main power supply, it can counteract all harmonic currents present before they can reach the transformer or generator. In this case, however, any harmonic currents present will be able to flow through a bigger part of the electrical installation. Filtering on the main power supply is a very useful solution when a large number of small harmonic-inducing devices are collectively causing large amounts of harmonic pollution.

Two typical characteristics

Fast response time

Our harmonic filters have a very fast response time, so that harmonic pollution and malfunctions are almost immediately detected and eliminated before they cause any damage or problems.

Adjustable and dynamic

The type of contamination the filter should focus on can be chosen by setting the appropriate parameters. Also, the degree to which this pollution should be eliminated can be set. The Active Harmonic Filter is dynamic and continuously adapts to changing conditions. Even at a later point in time, the parameters set in the Active Harmonic Filter can be adjusted. This makes the filter future-proof and effective throughout its lifetime. The adjustability is an important difference from the more static Passive Harmonic Filter.

Result of filtering harmonic currents

A transformer or generator has relatively high impedance, compared to the rest of an installation, especially for the higher frequencies harmonics consist of. If these harmonic currents flow through any impedance, they will introduce harmonic voltages. The higher the impedance, the higher the harmonic voltages. Especially when induced on the main power supply, these harmonic voltages can access the total installation and cause major problems. These are explained under ‘Harmonic pollution’.

When harmonic currents are counteracted by the Active Harmonic Filter, they can no longer flow through certain parts of the electrical installation – the transformer or generator in particular. When the harmonic currents no longer flow through these specific high impedance areas of the electrical installation, harmonic voltages will no longer be induced and Power Quality will greatly improve. For the best filtering results, filtering should take place as close to the source of pollution as possible.

Grafiek-zonder AHF met rode button
Chart power and voltage WITHOUT Active Harmonic Filter
Grafiek met AHF met groene button
Chart power and voltage WITH Active Harmonic Filter

Why a HyTEPS Active Harmonic Filter?

Harmonic pollution is a key characteristic of poor Power Quality. Over the years, HyTEPS – a specialist in the field of Power Quality – has gained a considerable amount of knowledge and experience in this field. This is the result of measuringanalyzing and solving the most complex Power Quality problems in a wide range of installations and sectors. We have the knowledge, experience and products to tackle harmonic pollution within each installation.

Advantages HyTEPS offers:

We have many years of experience and can, therefore, rapidly respond to potential problems
Through measurements, analyses and calculations we create the most suitable Active Harmonic Filter for your specific installation and situation
If required, we can offer your installer support during installation
Commissioning and reports are provided exclusively by our own engineers
We offer inspections, service and maintenance,  to ensure proper functioning of the Active Harmonic Filter
Harmonic compensation can be adjusted from the 2nd to the 50th harmonic with our filters
Each specific harmonic can be compensated to a desired level
An Active Harmonic Filter from HyTEPS can be read remotely via MODBUS communication over Ethernet
The response speed of our filters is <300μs, allowing rapid harmonic variations to be resolved without any problems
Due to the reaction speed, harmonic variations are solved quickly without problems
Settings on the Active Harmonic Filter are easy to change and monitor
The filter easily can adapt to changing loads
The Active Harmonic Filter can also be set to compensate for current unbalance between phases, reducing the voltage unbalance to a minimum.

Contact us

Interested in the possibilities for your organization? HyTEPS would be happy to help you! Fill out the form and we will contact you as soon as possible.

HyTEPS Engineer

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