The Basic Introduction of Active Harmonic Filter

Nowadays, in the realm of electrical engineering, Active Harmonic Filters (AHFs) have become increasingly important in addressing power quality issues. As our world becomes more interconnected and technologically driven, the demand for efficient, reliable, and clean electrical energy continues to surge. Consequently, harmonics—unwanted electrical frequencies that can interfere with power systems—pose a significant challenge for both consumers and suppliers.

The purpose of this book is to provide a concise and easy-to-understand description of how active harmonic filters work, their characteristics, why they are used, the size of active harmonic filters, their price, their comparison with passive harmonic filters, and to end with a list of well-known manufacturers who are very specialized in the field of active harmonic filters. Regardless of their backgrounds in the field, the complexity of AHF is revealed in a way that is easy for the reader to understand.

What is an Active Harmonic Filter?

In the 1970s, Harmonic Filters were born! Active Harmonic Filters (AHFs) tackled the growing challenge of power quality, thanks to the rise of nonlinear loads. Like superheroes, AHFs use power electronics and smart algorithms to fight off pesky harmonic distortions in power systems. They zap in compensating currents, neutralizing unwanted harmonics, and keeping the power supply clean and stable. AHFs play a vital role in protecting sensitive gadgets, boosting energy efficiency, and preventing costly downtime in places like data centers, factories, and fancy commercial buildings with intricate electrical setups.

Working Principle of Active Harmonic Filter

Let me explain to you the principle of active harmonic filters in an interesting way!

Imagine the Active Harmonic Filter (AHF) as a musical conductor who fine-tunes the performance of an orchestra. In a power system, AHF listens to the "noise" created by unwanted harmonics and then "conducts" a counter-performance that cancels out the bad sounds.

To do this magic, AHF detects the troublesome harmonics in the system and quickly calculates the right countermeasures. It then sends out compensating currents that are equal in strength but opposite in phase to the unwanted harmonics. These currents dance together, perfectly choreographed, and effectively cancel each other out.

The result? A power system that sings in harmony, with a cleaner and more stable power supply for all the electrical equipment to enjoy!

Why choose Active Harmonic Filter?

Because active harmonic filters effectively neutralize unwanted harmonics by injecting compensating currents, they ensure a cleaner, more stable power supply. While at the same time protecting sensitive electronic equipment, improving energy efficiency and minimizing the risk of costly downtime.

Because of AHF's outstanding capabilities, it is used in a wide variety of industries and facilities with high power quality requirements. Some common applications include:

• Data centers: Ensuring uninterrupted operation and protecting servers and other sensitive equipment from harmonics.

  
  

• Manufacturing plants: Maintaining the performance and reliability of electrically driven machinery, robotic systems, and automation equipment.

  
  

• Commercial buildings: Optimize the power quality of complex electrical systems and improve the performance of HVAC, lighting, and other building systems.

  
  

• Healthcare Facilities: Ensure proper operation of life support and medical imaging equipment.

  
  

• Renewable Energy Systems: Improve the power quality of solar inverters, wind turbines, and other renewable energy sources.

  
  

• Electric Vehicle Charging Stations: Maintain optimal power quality during charging and protect the vehicle's on-board electronics.

In this way, operators can operate smoothly and reliably, while reducing energy waste and extending the life of equipment.

Size of Active Harmonic Filters

The size of an active harmonic filter (AHF) depends on several factors, including capacity, design and application. The rating of an AHF is based on its current-carrying capacity, usually expressed in amperes (A). Common sizes range from a few amps to several hundred amps, and compact models may be as small as a briefcase, while larger units may be as large as a refrigerator or even larger. Commonly are 50A, 100A, 300A.  It depends on the degree of harmonic distortion and the size of the electrical system in which they are installed.

Different Types of Harmonic Filters

Harmonic filters are an important component of power systems to mitigate harmonic distortion and improve power quality. There are two main types of harmonic filters: passive and active filters. Each type has its specific applications and characteristics:

Passive Harmonic Filters:

Passive filters are the most common and traditional method of harmonic filtering. They usually consist of passive components, such as inductors, capacitors and resistors. One of these single-tuned filters can target a specific harmonic frequency so that they provide low impedance at the target frequency, allowing harmonic currents to flow through the filter and leave the power system.

In contrast, active harmonic filters are not as widely used.

Active Harmonic Filters:

Active filters use power electronics and control algorithms to dynamically mitigate harmonic distortion. They inject compensating currents into the power system to offset unwanted harmonics, resulting in a cleaner, more stable power supply. Active filters can be further classified as

• Active Harmonic Filters (AHFs): AHFs primarily mitigate harmonic distortion in a system by injecting harmonic currents that are equal in amplitude but opposite in phase to the unwanted harmonics.

• Active Power Filters (APFs): Active power filters address a wider range of power quality issues, including harmonic distortion, reactive power compensation and load imbalance.

They inject appropriate compensation currents to maintain a balanced and sinusoidal current waveform and reduce overall system distortion.

Both passive and active harmonic filters have their advantages and disadvantages. The choice of these filters depends on factors such as specific power quality issues, system characteristics, cost and maintenance requirements. In many cases, both passive and active filters can be used to achieve the desired level of harmonic mitigation and power quality improvement.

In order to show the difference between active and passive harmonic filters in more detail, we have made a table:

Aspect	Active Harmonic Filters (AHFs)	Passive Harmonic Filters (PHFs)
Principle	Use power electronics and control algorithms to inject compensating currents that cancel out harmonic distortions.	Utilize passive components like inductors, capacitors, and resistors to create low impedance paths for harmonic currents.
Adaptability	Highly adaptive and can respond dynamically to changes in the system and harmonic content.	Fixed, designed for specific harmonic frequencies, and less adaptive to changes in the system.
Efficiency	Can target multiple harmonics with high accuracy and efficiency.	Efficiency depends on filter design and can be less effective in systems with a wide range of harmonic frequencies.
Reactive Power	Capable of compensating for reactive power and load imbalances.	Primarily focused on harmonic mitigation, with limited capability to address reactive power or load imbalances.
Installation	Relatively easy to integrate into existing systems, as they do not require significant changes to the network.	May require complex installation procedures and additional passive components for tuning and impedance matching.
Maintenance	Require regular maintenance due to the presence of power electronics and other active components.	Generally low maintenance as they consist of passive components with no moving parts or active elements.
Cost	Initial costs can be higher due to the use of power electronic devices and control systems.	Often less expensive initially, but may require additional components and maintenance in the long run.
Space Requirement	Typically compact and require less space compared to passive filters.	Can require more space due to the need for large inductors, capacitors, and resistors.

The Price of Active Harmonic Filters

The price of Active Harmonic Filters (AHFs) varies depending on factors such as capacity, design, features, and manufacturer. It is difficult to provide specific prices, as they change with market conditions and product offerings. However, to give you a general idea, here are some approximate price ranges for different capacities of AHFs:

50 A: The cost of a 50 A AHF can range from $5,000 to $10,000.

100 A: A 100 A AHF may be priced between $10,000 and $20,000.

300 A: Larger 300 A AHFs can cost anywhere from $25,000 to $40,000 or more.

Well-known Manufacturers of Active Harmonic Filters

If you want to buy active harmonic filters, but are confused about which manufacturer to choose, here are some references:

• ABB

• Schneider Electric

• Eaton

• Siemens

• Danfoss

• Schaffner

• MTE Corporation

In this article, we explore the fundamentals of harmonics, delve into the various types of AHF, and discuss their practical applications across a wide range of industries. I believe you have gained a different perspective on the importance of these filters in today's power hungry world.

Our goal is to give you an understanding and appreciation of Active Harmonic Filters and their critical role in maintaining the integrity of modern power systems. Whether you are an engineer, technician, student, or just curious about the fascinating world of electrical engineering, we hope this article is helpful to you.

If you want to know more about these areas, come to our homepage and contact us, we’re looking forward to hearing your voice!

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