What is an Active Harmonic Filter (AHF)?
Background Information
Ensuring optimal power quality is crucial in today's industrial and commercial settings for reliable and efficient operations. The increasing use of non-linear loads, such as inverters, rectifiers, and cycloconverters, introduces disturbances i.e. harmonic currents and reactive power into the grid that impact power quality. Research indicates that overheating of equipment, electrical losses and subsequent downtime, leading to financial losses, are directly linked to poor power quality.
Power quality disturbances like harmonic distortion, voltage fluctuations, and a low power factor have become common and can be costly if not addressed.
Why Power-Quality Disturbances Matter
Unchecked harmonics and related issues can lead to:
Equipment overheating and premature failure
Nuisance of VFD tripping or unplanned downtime
Poor power factor - inefficient power consumption and financial loss
Voltage distortion that propagates to adjacent tenants or utility feeders
Higher maintenance and replacement costs (increasing operational costs), etc.
Research shows that more than 30 % of industrial downtime is power-quality related, directly impacting productivity and profitability.
To mitigate these issues, Active Harmonic Filters (AHFs), sometimes marketed as Active Dynamic Filters (ADFs), have become a key solution for modern electrical systems.
What is an Active Harmonic Filter (AHF)
Active Harmonic Filters (AHFs) are electrical devices designed to actively mitigate or eliminate harmonic distortion in power systems in real-time. Harmonics, which are voltage or current waveforms at integer multiples of the fundamental frequency, can cause inefficiencies and overheating in electrical equipment. AHFs play a crucial role in maintaining power quality, improving system efficiency, and extending the lifespan of electrical devices.
In contrast to traditional passive filters, which tend to be bulky and less effective, AHFs are compact, flexible, and highly efficient. They employ advanced technology, algorithms, and real-time monitoring to dynamically adapt to changing power conditions, ensuring that electrical systems operate safely and efficiently. This adaptability makes them particularly well-suited for modern systems with dynamic loads.
How Active Harmonic Filters Work
Active harmonic filters operate by detecting and compensating for harmonic currents in real-time. Utilizing advanced technology, they analyze electrical signals and generate counteracting currents to effectively neutralize unwanted harmonics. This process helps restore the sinusoidal waveform of the current, ensuring that the power supplied to the equipment remains clean and efficient. The following video demonstrates how this process works.
Key components of Active Harmonic Filters
Current Sensors: These devices continuously monitor the electrical current within the system to detect harmonic distortions.
Digital Control Algorithms: Advanced algorithms, typically based on FFT or PQ theory, process sensor data, decompose the waveform into harmonic and fundamental components, and determine the compensating currents required to mitigate the harmonics.
Power Processor: This component produce the compensating currents and introduce them into the power system to effectively neutralize the harmonics.
The following figure demonstrates the operation of an AHF:
The Active Harmonic Filter (AHF) is connected in parallel to the load needing compensation. It monitors electrical current flows to identify issues like reactive displacement and harmonics. A control computer processes these measurements to generate a control signal for a power processor, which creates a compensation current. This current is injected into the network to neutralize disturbances, resulting in minimal power losses and a clean power supply with a pure sinusoidal waveform. The filtering operates in real-time (< 1 ms).
Benefits of Using Active Harmonic Filters
Improved Power Quality: AHFs enhance the overall quality of power by reducing total harmonic distortion (THD), which can lead to better performance of electrical equipment.
Increased System Efficiency: By minimizing harmonics, active filters help reduce energy losses, leading to lower electricity bills and improved system efficiency.
Equipment Protection: They protect sensitive equipment from damage caused by overheating and other issues related to harmonic distortion.
Compliance with Standards: Many industries must adhere to specific power quality standards; active harmonic filters help ensure compliance with these regulations.
Fast response time suitable for dynamic loads: With response times less than 1 ms, ADFs can quickly follow and adapt to today’s dynamic loads.
Automatic adaption to load changes: AHFs automatically adjust to changes in load or installation conditions in real-time.
Power factor correction: They improve the overall power factor of the system.
Load balancing: AHFs contribute to load balancing, handling imperfections and unbalances in the installation, load, or grid voltage.
ADFs enhance multi-pulse drive applications by compensating for transformer design limitations and residual harmonics. Adding an ADF can significantly improve performance.
For multiple non-linear loads, a global compensation approach using a centralized filter is often more cost-effective (50% to 83% less) than local compensation. Global compensation reduces size and weight, offering installation and maintenance flexibility. Using sizing tools and considering grid standards can lead to a more economical solution.
Real-World Application of AHF
Active harmonic filters are widely used in various sectors, including:
Industrial Facilities: To mitigate harmonics generated by variable frequency drives (VFDs) and other non-linear loads.
Commercial Buildings: To improve power quality in office buildings, data centers, and retail spaces.
Renewable Energy Systems: To manage harmonics produced by solar inverters and wind turbines.
For instance, a packaging facility in Brisbane experienced frequent failures of PLC-controlled machinery. After the installation of a centralized Active Harmonic Filter (AHF), harmonic levels decreased from 16% THD to below 3%, and the power factor improved to 0.99. This ensured compliance with power quality standards, enhanced equipment safety, reduced unscheduled downtime by 42%, and extended equipment lifespan.
In another case, a large mining conveyor in Pilbara faced overheating issues with their multi-pulse drive and transformer. Following the installation of a centralized AHF, harmonic levels were reduced, resulting in a decrease in transformer temperature by 8°C and annual energy savings exceeding 95,000 AUD.
Industry Case Stories
Manufacturing facility – Injection-moulding machines overheated due to 5th/7th harmonic current. After AHF deployment, current distortion fell below 3 %, stabilising motor temperatures and protecting existing capacitor banks.
Bakery production line – Sporadic generator trips stalled mixers and ovens. A skid-mount AHF cleaned the generator voltage waveform, eliminating nuisance shutdowns and ensuring every bake cycle runs to schedule.
Entertainment venue – Variable-speed drives on thrill rides caused flicker and PLC errors. A roof-top AHF restored a smooth 50 Hz waveform, meeting local council flicker limits and guaranteeing passenger safety.
Grain storage facility – Poor power factor (0.89) and 6 % voltage distortion attracted utility penalties. After AHF deployment, it raised PF to 0.99, cut distortion to 2 % and provided remote web monitoring for the site electrician.
These results mirror challenges across Australian food processing, agriculture, manufacturing and leisure sectors, demonstrating that AHFs deliver measurable ROI and risk reduction.
Australian Standard & Compliance
Installing AHFs improves performance and ensures compliance with international standards such as:
IEEE 519-2022 – Harmonic limits for public and private networks
IEC 61000-3-2 / 61000-3-12 – Emission limits for LV installations
IEC 61000-6-2 (immunity) and IEC 61000-6-4 (emission) for industrial environments
AS/NZS 61000 series adoption in Australia
In summary, active harmonic filters (AHFs) play a crucial role in modern electrical systems by improving power quality and efficiency. They are essential tools for harmonic mitigation and maintaining electrical system reliability, offering substantial economic and technical advantages for modern power systems. Their ability to dynamically compensate for harmonic distortion makes them an essential investment for industries and facilities looking to optimize their electrical systems and protect their equipment. They are a smart investment for any facility operating modern, non-linear electrical loads.
How PulseTech Can Help You
PulseTech offers Active Harmonic Filters to reduce harmonic currents and improve power quality per Australian standards. As a leading specialist, we use advanced tools like the PQBox 300 for power quality analysis, providing tailored solutions for commercial and industrial clients.
We also offer harmonic modeling and simulation services with PSCAD and PowerFactory for precise design validation, ensuring reliable and efficient solutions.
Key product features:
Compact, service-friendly wall-mount or rack-mount enclosures
Integrated web-UI—no extra software installation required
Designed to be safe and user-friendly
Expandable modular system
Compliant with Australian standard
Nationwide commissioning and extensive support across Australia
Get Expert Advice Today
Our team of specialists can help you:
Assess your system’s current harmonic and power factor levels.
Identify the right solutions for your application.
Deploy an optimized AHF solution with guaranteed compliance.
Monitor and maintain long-term efficiency.
We offer solutions to ensure your system remains efficient and compliant. Contact our certified power-quality specialists to schedule a site study and discover how an Active Harmonic Filter can safeguard your plant, cut energy waste and future-proof your system.