How Does An Active Harmonic Filter Work?

An active harmonic filter is a device used to mitigate the presence of harmonic currents and voltages in electrical systems. Harmonics are unwanted frequencies that can cause disruptions and inefficiencies in power systems. These disruptions can lead to equipment malfunction, increased energy consumption, and even fines for non-compliance with power quality standards. Active harmonic filters are designed to analyze the harmonic content of the electrical system and then generate corrective currents to cancel out the harmonics, thus improving the overall power quality.

How Active Harmonic Filters Work

Active harmonic filters operate by continuously monitoring the electrical system for harmonic distortion. Once the harmonic content is identified, the active harmonic filter generates a set of inverse currents to neutralize the harmonics. This is achieved by using power electronic devices such as insulated gate bipolar transistors (IGBTs) to generate the corrective currents. These currents are injected into the electrical system to cancel out the harmonic currents, thus ensuring that the load receives clean, sinusoidal power.

Active harmonic filters are typically connected in parallel with the non-linear loads, such as variable frequency drives (VFDs), uninterruptible power supplies (UPS), and other power electronics that are known to introduce harmonics into the system. By actively monitoring and compensating for the harmonics, the active harmonic filter helps in maintaining the quality of the power supply and prevents the distortion from affecting other connected equipment.

Benefits of Using Active Harmonic Filters

There are several benefits to using active harmonic filters in electrical systems:

  • Improved Power Quality: By mitigating harmonics, active harmonic filters ensure that the power supplied to the load is clean and free from distortions.
  • Energy Savings: Harmonic distortion can lead to increased energy consumption due to the inefficiencies it causes in the electrical system. By eliminating harmonics, active harmonic filters help in reducing energy wastage.
  • Extended Equipment Lifespan: Electrical equipment is designed to operate with clean sinusoidal power. The presence of harmonics can lead to overheating and premature failure of equipment. Active harmonic filters help in extending the lifespan of connected equipment.
  • Compliance with Standards: Many countries and regions have regulations and standards regarding the level of harmonic distortion permissible in electrical systems. By using active harmonic filters, businesses can ensure compliance with these standards and avoid penalties for non-compliance.

Overall, active harmonic filters play a crucial role in maintaining the reliability and efficiency of electrical systems, especially in environments where non-linear loads are prevalent.

Benefits of Active Harmonic Filters

Active harmonic filters offer a range of benefits for electrical systems, making them an essential component in many industrial and commercial applications. One of the primary advantages is their ability to improve power quality by reducing harmonic distortion. Harmonic distortion can cause a variety of problems, including overheating in transformers and motors, voltage fluctuations, and even equipment damage. By mitigating these harmonics, active harmonic filters help to extend the lifespan of electrical equipment and improve overall system efficiency.

Another significant benefit of active harmonic filters is their ability to reduce energy consumption. Harmonics can lead to increased power losses and reduced power factor, resulting in higher energy bills. Active harmonic filters counteract these losses by compensating for the reactive power and reducing the overall energy consumption of the system. This can lead to substantial cost savings for businesses, especially those with high-energy usage or stringent power quality requirements.

Improved System Reliability

Active harmonic filters also contribute to improved system reliability by protecting sensitive electronic equipment from the damaging effects of harmonics. Harmonics can cause voltage distortion, which can lead to malfunctions or premature failure of devices such as computers, medical equipment, and industrial control systems. By maintaining a clean and stable power supply, active harmonic filters help to ensure the reliable operation of these critical systems, reducing the risk of downtime and costly repairs.

Furthermore, active harmonic filters can help businesses meet regulatory compliance requirements. Many countries and regions have implemented power quality standards that set limits on the amount of harmonic distortion allowed in electrical systems. Active harmonic filters can help businesses comply with these regulations, avoiding potential fines or other penalties for non-compliance.

Versatile Applications

Active harmonic filters are versatile and can be deployed in a wide range of applications. They are commonly used in industrial settings, such as manufacturing plants, mining operations, and wastewater treatment facilities, where non-linear loads are prevalent. Active harmonic filters are also increasingly being used in commercial buildings, such as office complexes, hospitals, and data centers, where power quality is essential for the proper functioning of sensitive electronic equipment.

In addition, active harmonic filters can be integrated into renewable energy systems, such as solar and wind power installations. These systems often generate harmonics due to the power electronics involved, and active harmonic filters can help to mitigate the impact of these harmonics on the grid and other connected systems.

Selecting the Right Active Harmonic Filter

When choosing an active harmonic filter, it’s important to consider the specific requirements of the electrical system. Factors such as the size of the system, the type and number of non-linear loads, the required level of harmonic mitigation, and the available space for installation should all be taken into account.

It’s also important to select an active harmonic filter with the appropriate power rating and compensation capabilities. Active harmonic filters are available in a range of power ratings, from a few kilowatts to several megawatts, and they can be configured to compensate for different types of harmonics, including current and voltage harmonics.

In addition to the technical specifications, it’s important to consider the overall cost of ownership, including the initial purchase price, installation costs, and ongoing maintenance requirements. Active harmonic filters can represent a significant investment, but the long-term benefits in terms of improved power quality, energy savings, and system reliability can often justify the upfront cost.


Active harmonic filters play a critical role in maintaining the quality and efficiency of electrical systems. By continuously monitoring and compensating for harmonic distortion, these devices help to prevent a wide range of problems, from equipment damage to energy waste. As businesses and organizations increasingly focus on improving their environmental footprint and reducing their energy costs, active harmonic filters will continue to play a vital role in ensuring the reliability and sustainability of electrical infrastructure.

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