What is an Active Harmonic Filter, and why might you need one?

Active Harmonic Filters are installed to reduce, or mitigate, harmonics by using a set of transistors and capacitors to filter (or clean) the current wave by injecting inverse currents to cancel out the undesired harmonic components. With minimised harmonics, you are ultimately optimising your power supply.

An Active Harmonic Filter, also known as an Active Power Filter, can help improve power quality and protect your electrical system. Enhance efficiency and reduce energy costs.

Uses and benefits

Active Harmonic Filters are essential for maintaining optimal power quality in electrical systems. They effectively eliminate harmonic pollution, balance loads, and correct power factor, ensuring smooth and efficient operation. By reducing waveform distortion and preventing overheating, these filters protect equipment from damage and lower maintenance costs. Additionally, they mitigate voltage drops and temperature rise in transformers and cables, further enhancing the reliability and efficiency of your power system. Investing in Active Harmonic Filters is a proactive step towards safeguarding your electrical infrastructure and improving overall energy efficiency. Here are the top 6 uses and benefits:

  • Eliminate harmonic pollution
    Harmonic voltages and current in an electric power system are the result of non-linear electric loads. Harmonic frequencies within the power grid are a frequent cause of power quality problems.
  • Power Factor and Load Balancing capabilities
    As the active harmonic filters are measuring each phase, they can redirect existing load currents to balance the phases. Additionally, remaining compensation capacity can be utilised to correct power factor by injecting reactive power into the power system.
  • Protect your electrical system
    The presence of harmonics in electrical systems can lead to potential damage of equipment, disrupting regular functioning of devices and leading to increased running costs. The use of filtering in cases of harmonic distortion can reduce overheating of equipment and nuisance tripping of circuit breakers and fuses. It can also improve power quality contributing to reduced energy costs.
  • No risk of harmonic resonance
    Infinite impedance to grid avoids potential harmonic resonance problems.
  • Significantly reduce voltage waveform distortion
    As voltage harmonics are instigated by current harmonics flowing through system impedance, the implementation of active harmonic filters in electric power system will also mitigate voltage distortion (voltage distortion, or THDv.
  • Reduced voltage drop and temperature rise on transformer & cables
    Current harmonics increase the RMS current flowing in an electric power system and thereby, increase the power losses. These increased currents and losses in transformers and electric motors result in over-heating and overloading in neutral conductors.

How an Active Harmonic Filter works

Before we can describe how an Active Harmonic Filter works, lets dive in deep and describe what harmonics are?

Harmonics are that part of a signal whose frequencies are integral multiples of the system’s fundamental frequency. For example, with a 50Hz fundamental frequency (which we operate on in Australia), we can expect harmonics at 100Hz (2nd order harmonics), 150Hz (3rd order), 200Hz (4th order), and so on. Alternating current (AC) and voltage waveforms, when representing the fundamental frequency, are sinusoidal. 50Hz simply means the sinusoidal waveform occurs 50 times each second. Harmonics of the third order, for example, occur 150 times per second; fifth order harmonics 250 times per second and so on.

All AC waveforms deviate from the ideal sinusoidal shape due to the different harmonics present in the electrical system. We call such waveforms distorted or complex waveforms.

Basically, everything we do in an attempt to increase reliability and/or save money with regard to efficient electrical equipment creates an issue with regard to harmonic propagation. The introduction of LED lighting, adoption to variable speed drives, uninterruptible power supplies (UPS), HVAC systems, lift and escalator systems and other non-linear loads result in the propagation of harmonics. A load is said to be non-linear when the waveform associated with the current is not the same as waveform associated with the voltage.

Supply Authorities (e.g. TasNetworks, Essential Energy, Western Power, Energex, Ergon Energy, SA Power Networks, Citipower and Powercor, etc.), monitor the degree of distortion at the point of common coupling (PCC) – basically where a consumer connects to the electricity grid – and the customer has a responsibility to ensure the harmonic levels are within the limitation set forth in the relevant Australian Standards. If a customers installation is found to be outside of the level outlined in AS61000 the supply authority will request harmonic filtering be installed.

How does an Active Harmonic Filter reduce harmonics?

The Active Harmonic Filter works in much the same way as the Static Var Generator (to learn more about what a Static Var Generator is click here) in that The AHF monitors the load current in real time through external current transformers (CT’s) and through the internal firmware of the device determines the harmonic component of the load current. The device then generates a current with an amplitude in the inverse direction to that individual harmonic – essentially cancelling it out.

Active harmonic filters are installed parallel to the load (which means the current doesn’t go through the filter) and are used to reduce, or mitigate, harmonics to tolerable levels as defined by AS61000.3.6 and IEEE-519. Active filters use a set of transistors and capacitors to filter (or clean) the current wave by injecting inverse currents to cancel out the undesired harmonic components.

Why should you purchase an Active Harmonic Filter from Enginuity Power Solutions?

When you choose our Active Harmonic Filter product, you are choosing the most simple, turnkey solution to improve your power quality and meet Australian Standards.

To set you up with the solution for your specific application, all we need is some very basic information that you or any maintenance electrician can easily gather. Our team then takes this data and, using a series of automated calculators, we can quickly match you with the right solution. This cuts out the need for on-site studies by engineering teams or specialist contractors which saves you time and money.

We will then ship out the product with all mounting configuration, current transformers, cabinet, and all other infrastructure required to fit on site. Commissioning and technical support is provided throughout the installation process.

Our Active Harmonic Filter equipment is certified for the Australian market and tested to the following standards:

IEC 61000-6-2:2019
IEC 61000-6-4:2019
IEC 62477-1:2012

**Certificate of Conformity EMC issued by TUV Rheinland

How do you know if you need an Active Harmonic Filter?

To help determine whether you need an Active Harmonic Filter, Enginuity Power Solutions can help quickly assess your situation and provide guidance. Our products are turnkey solutions and can usually be installed with minimal disruption by a qualified electrician. We also have engineers available to assist. The simplest way forward is to get in touch.

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