Active Harmonic filters use IGBT fired circuits to mitigate harmonic distortions in the load or the network of loads where they are installed. They can be separately installed on prominent individual loads generating harmonics or combined AHF unit on mains. The combination of both can also be used. It all depends on level of harmonics, type of operational issue for which it is being installed or level of compliance to standards as per utility / distribution company.
Active Harmonic Filter eliminate harmonic injected into the mains supply by non-linear loads. Its response time is extremely fast and is connected in parallel to the load which is to be compensated.
Current harmonic elimination is achieved by sensing load current & extracting harmonic current signal. This and the reactive current signal, together are used to generate a reference for the controlled current source connected at the PCC (point of common connection) of source and load. This results in Mains supplying only real power for the load and reactive & harmonics being sourced from the AHF. This is carried out dynamically, so that any change in the load pattern or its nature is immediately responded without any manual intervention.
