Active harmonic filter

Overview

Active harmonic filter is a new type of equipment specifically designed for electrical harmonic mitigation. The active harmonic filter consists of two main components: a command current calculation circuit and a compensation current generation circuit. The command current calculation circuit monitors the line current in real time and converts the analog current signal into a digital signal. This signal is then fed into a high-speed digital signal processor (DSP) for signal processing, separating the harmonics from the fundamental wave. The DSP then sends drive pulses in the form of pulse-width modulated (PWM) signals to the compensation current generation circuit, which drives the IGBT or IPM power module. This generates a compensation current with equal amplitude and opposite polarity to the grid harmonic current, which is then injected into the grid to compensate or offset the harmonic currents, actively eliminating power harmonics.

Lafaelt active harmonic power 6.0 is an advanced solution to solve the harmonic problem with IGBT/SIC. Our active power filter offters a selectable priority function of harmonic filtering, power factor correction(reactive power compensation) and Three-phase imbalance regulation.

Working Principle

An active harmonic filter is an electronic circuit composed of active devices (such as operational amplifiers and transistors) and passive components (resistors and capacitors). Its core function is to selectively amplify or attenuate signals of specific frequencies, thereby achieving frequency filtering of the input signal. Its principle can be broken down as follows:

Active devices: Typically, operational amplifiers (Op-Amp) provide signal amplification, buffering, isolation, and impedance matching.

Passive components: Resistors (R), capacitors (C), or less commonly, inductors (L) form a frequency-selective network that determines the filter's cutoff frequency and response characteristics.

Signal input: The input signal passes through the frequency-selective network composed of RC (or RLC). Different frequency components produce different impedance responses in the circuit.

Frequency selection: By adjusting the parameters of the RC network, impedance matching is achieved for the target frequency signal while suppressing signals of other frequencies.

Amplification and feedback: The operational amplifier amplifies the selected frequency signal and precisely controls the gain and filtering characteristics through a negative feedback network (such as a multiple feedback topology or Sallen-Key structure). Synthesized output: In the final output signal, the target frequency band is retained (for example, the low-pass filter retains low frequencies, and the high-pass filter retains high frequencies), and other frequency components are attenuated.

Features

1. Suppresses harmonic currents generated by non-linear loads

2. More than 97% harmonic filtering rate

3. Even times harmonic mitigation, 2nd, 4th, 6th harmonics problem solving.

4. Automatic detuning eliminates system resonance concerns

5. Customized HMI for wall mounted or rack mounted type 

6. Reduces line and transformer losses, improves equipment overheating, and extends equipment life

7. 80KHz switching frequency

8. Three-phase imbalance regulation

9. Wall mounted type for non-space or small project

What is active harmonic filter?

In 1969, B.M. Bird and J.F. Mars first proposed the concept of an active power filter in their paper. By injecting third harmonic current into the power grid, they reduced the harmonic content in the current and improved the current waveform. This was the beginning of the active harmonic filter. 

In 1971, H. Sasaki and T. Machida of Japan first fully described the basic principles of the active harmonic filter. By generating a compensating current of equal magnitude and opposite direction to the load harmonic current, they offset the load harmonic current, thereby achieving power grid purification. 

In 1976, L. Gyugyi and E.C. Strycula of Westinghouse Electric Company in the United States proposed an active power filter using PWM control. This established the basic circuit topology and control method of the AHF active harmonic filter, laying the foundation for the development of active filters. With the widespread operation of power electronic devices in today's power grid, harmonics have become widely recognized as a "pollution" and "public nuisance" to the power system. They degrade the quality of voltage and current, impacting the operation of the power system itself, and posing a threat to users and surrounding communications systems.

Lafaelt's AHF utilizes power electronics technology and intelligent algorithms to eliminate harmonic distortion in power systems. They rapidly inject compensating current to neutralize unwanted harmonics, maintaining clean and stable power. In data centers, factories, and high-end commercial buildings with complex electrical systems, AHF plays a vital role in protecting sensitive equipment, improving energy efficiency, and avoiding costly downtime.

Why choose active harmonic filter?

Active harmonic filters effectively neutralize harmful harmonics by injecting compensating currents, ensuring a cleaner, more stable power supply. They also protect sensitive electronic equipment, improve energy efficiency, and minimize the risk of costly downtime.

Due to their superior performance, active harmonic filters (AHFs) are widely used in different industries and facilities where power quality is paramount. These are the applications:

Data centers: They ensure uninterrupted operation of server cabinets and protect all equipment from harmonics.

Manufacturing plants: They ensure the performance and stability of electric machinery and automation equipment in manufacturing plants.

Commercial buildings: They optimize the power quality of electrical systems and enhance the performance of other power equipment within the building.

Healthcare facilities: They ensure the proper operation of medical equipment.

Renewable energy systems: They address harmonics generated by loads such as inverters and turbines.

Electric vehicle charging stations: They maintain power quality while charging electric vehicles.

In summary, active filters can reduce harmonics at the load end, reduce energy waste, protect the safety of equipment and extend the service life of equipment.

Well-known Manufacturers of Active Harmonic Filter

• ABB

• Schneider Electric

• Eaton

• Siemens

• Danfoss

• Merus Power

• Comsys

• Circutor
  

• Lafaelt

Technical Parameters

Active Harmonic Filter Specification