Equipment such as drives, inverters, UPS, arc furnaces, transformers, filters and discharge lamps – in general known as non-linear loads – generate current and voltage harmonics into the grid network. Generated harmonics can lead to:

• Overheating of transformers and conductors
• Generators instability
• Power Factor Capacitor failure/ Reduced Operational Lifetime
• Nuisance tripping of fuses and circuit breakers
• Damage to sensitive electronic equipment including drive failure
• High energy costs
• Neutral cable overload

Harmonics effects can be reduced using passive harmonic filters, or completely canceled/eliminated using active harmonic filters

Passive Harmonic Filters:

A combination of reactors and capacitors to filter out harmonic frequencies. This kind of filters is useful with specific current and voltage distortion values but not for high distortion.    

Active Harmonic Filters:

In plants with high harmonic distortion values, passive harmonic filters will be not efficient. Thus, we use active harmonic filters. Connected in parallel with non-linear loads at the main feeder income, active filters generate a compensating current with the same amplitude but opposite phase angles to the detected harmonic current, this in advance eliminates harmonic voltage caused by harmonic currents, which cancels out the original load harmonics. Active harmonic filters in addition provide the following features:

• Reactive power compensation
• Phase Load balance
• Flicker compensation
• Compensation up to the 50th order of harmonic with high response time