Active Harmonic Filter (AHF)
is used for centralized harmonic suppression in a power system. Active Harmonic Filter in Chennai
is an IGBT based power electronics device. It uses IGBT and inverter technology.
It actively eliminates 100% harmonic distortion and reacts instantly to varying or Non linear loads. This is done by injecting additional currents as required in order to cancel the harmonic components of the non-linear loads.
Harmonics are unwanted frequency components and
unbalance in terms of uneven power distribution between the phases in the electrical network.
Harmonics are produced by electronic loads which draw currents in a "chopped" manner and the current drawn by these non-linear loads are non-sinusoidal in nature. The level of harmonics is usually expressed as a ratio called Total Harmonic Distortion,
THD% = (RMS value of all harmonics) / (RMS value of the fundamental) in %.
The harmonic currents passing through linear loads generate harmonic distortion in the voltage wave shape, which will depend on both the nature of the harmonic currents and the impedance of the grid and loads. The harmonics norms in India, consistent with international
standards like IEEE 519, have been fixed by the Central Electricity Authority (CEA) in their Technical Standards for Connectivity to the Grid Regulations,2007. The regulations stipulate that the total harmonic distortion for voltage at the connection point shall not exceed 5% with no individual harmonic higher than 3% and the total harmonic distortion for current drawn from the transmission system at the connection point shall not exceed 8%. Now Power Utilities
like TNEB have started levying penalties on consumers not only for low power factor but also when harmonics exceed the CEA norms.