AHF is abbreviation of Active Harmonic Filter.
Active Harmonic Filter is shunt connected harmonic eliminator. It consists self-commutated, IGBT switches. It keeps supply side harmonic distortion within IEEE 519 limit. AHF also improves power factor at supply side by injecting reactive current in to grid.
Operating principle
Harmonic Generation operation: Harmonic current will be extracted from sensed load current and equal amount of harmonic current will be generated and fed in to grid for harmonic suppression.
Control operation: Control algorithm will extract the harmonic current from the sensed load current. It will generate gate pulse required to suppress the harmonic current.
