Active harmonic filters (AHFs) are advanced power quality devices designed to reduce harmonic distortion and improve power quality in electrical systems. Harmonic distortion is caused by the presence of non-linear loads in a power system, such as computers, variable frequency drives, and other electronic devices. These non-linear loads introduce harmonic currents into the system, which can lead to voltage distortion, overheating of equipment, and increased losses.
Active harmonic filters work by actively monitoring the current waveform of the electrical system and injecting equal and opposite harmonic currents to cancel out the harmonic components, thereby mitigating the harmful effects of harmonics. Here's how they achieve this and improve power quality:
Current Sensing and Monitoring: Active harmonic filters continuously monitor the current waveform of the system using sensors or current transformers. These sensors provide real-time information about the harmonic content and other power quality issues in the system.
Harmonic Detection: The active harmonic filter analyzes the current waveform to detect the presence and amplitude of harmonic frequencies. It identifies the specific harmonic orders that need to be mitigated.
Current Injection: Once the active harmonic filter identifies the harmonics, it generates and injects equal but opposite currents at those harmonic frequencies into the system. These injected currents are designed to cancel out the harmonic currents generated by non-linear loads.
Instantaneous Compensation: Active harmonic filters provide instantaneous compensation, reacting quickly to changes in the system's harmonic content. This rapid response ensures that the harmonic distortion is minimized in real time.
Adaptive Control: Many advanced active harmonic filters employ adaptive control algorithms that adjust the compensation strategy based on the changing load conditions and harmonic profiles of the system. This adaptability ensures effective harmonic mitigation across varying operating conditions.
Improved Power Quality: By canceling out harmonic currents, active harmonic filters reduce the harmonic distortion in the system. This leads to improved power quality, including reduced voltage distortion and flicker, which can help prevent equipment malfunction, overheating, and premature failures.
Compliance with Standards: Electrical systems must adhere to power quality standards set by organizations such as IEEE and IEC. The use of active harmonic filters can help businesses and industries meet these standards by maintaining acceptable levels of harmonic distortion and other power quality parameters.
Energy Efficiency: Reducing harmonic distortion also results in reduced losses in the electrical system. By mitigating harmonics, active harmonic filters contribute to energy savings and lower operational costs.
Mitigation of Penalties: In some regions, utilities impose penalties on consumers for exceeding certain harmonic distortion limits. Using active harmonic filters can help businesses avoid these penalties.
Scalability: Active harmonic filters can be designed to handle a wide range of system sizes and harmonic loads. They can be integrated into both low-voltage and medium-voltage systems, making them adaptable to various industrial and commercial applications.
In summary, active harmonic filters actively monitor and counteract harmonic currents in electrical systems, resulting in reduced harmonic distortion, improved power quality, enhanced equipment lifespan, and potential energy savings.