Active Harmonic Filter: Complete Guide to Power Quality Improvement

Introduction

Modern industrial and commercial electrical systems increasingly use devices with nonlinear characteristics. Even with sinusoidal voltage, nonlinear devices draw distorted currents, causing harmonics. These harmonics lead to:

• Equipment malfunction
• Capacitor and transformer failures
• Increased energy losses
• Reduced system efficiency

Nonlinear loads generating harmonics include:

• LED and CFL lighting
• Switch Mode Power Supplies (SMPS)
• Variable frequency drives (VFDs)
• UPS systems
• Arc furnaces and SCR controllers
• Battery chargers & rectifiers

Impact of Harmonics

a. Grid Side

• Reduced generation and transmission efficiency
• Aging and premature failure of electrical equipment
• Overloading and failure of transformers, capacitors, and neutral conductors
• De-rated T&D capacity in several areas

b. Customer Side

• Overheated transformers, motors, and cables
• Power factor capacitor failures
• Spurious tripping of protective devices
• Increased losses leading to higher energy bills

c. Power Factor

Harmonics reduce the effectiveness of conventional power factor correction. True power factor includes displacement and distortion factors, which can only be improved with harmonic mitigation.

Harmonic Study and Standards

Harmonic Analysis

• A proper power quality audit documents:
• Harmonic current and voltage levels
• THDi (Total Harmonic Distortion of Current)
• TDD (Total Demand Distortion)

Standards

• IEEE Std. 519-1992
• CEA Grid Connectivity Regulations, 2007

Key Parameters:

• PCC (Point of Common Coupling) – utility/customer interface
• Isc/IL Ratio – short-circuit to load current ratio
• TDD – harmonic current relative to max demand load

Active Harmonic Filter: Connection Principles

How it Works:

• Connected in parallel (shunt) to 3-phase systems
• Measures load current via CTs
• Injects compensating currents 180° out of phase with harmonics
• Cancels harmonic currents effectively

Installation Locations:

• Electrical distribution panels
• Transformer secondary
• Individual high-harmonic loads

Applications and Benefits

Power Factor Improvement:

• Reduces reactive power (kVAR) locally
• Improves true power factor
• Reduces THDi, transformer & cable losses
• Enhances system capacity

Additional Benefits:

• Mitigates voltage fluctuations
• Extends equipment life
• Avoids penalties from utility regulations

Case Studies

Figure Suggestions:

• Harmonic percentage before vs after AHF (for each case study)
• Diagram of AHF shunt connection
• Power factor improvement chart

Image Alt Text Examples:

• “Active Harmonic Filter installation at industrial plant”
• “THDi reduction after AHF installation”
• “Power factor improvement using InPhase Active Harmonic Filter”

Conclusion

• Installing an Active Harmonic Filter provides:
• Reduced total harmonic distortion (THDi)
• Improved true power factor
• Reduced transformer & cable losses
• Extended equipment life
• Compliance with IEEE & CEA standards

Call-to-Action:
For expert Active Harmonic Filter solutions, contact InPhase Power Solutions today to enhance industrial power quality and energy efficiency.