Can an Active Harmonic Filter (AHF) be used in an electrical system that also has Passive Harmonic Filters (PHF) installed on some nonlinear system loads?
Active Harmonic Filters (AHF) can be installed on electrical systems that already have Passive Harmonic Filters (PHF) installed on some of the system's nonlinear loads. The PHF’s clean up a portion of the harmonics that are generated by the nonlinear loads which have PHF connected to them. The balance of the harmonic currents left in the system will be detected by the current transformers of an AHF if it is installed in parallel with the system's main supply bus terminals. The AHF will inject correction currents into the main bus to lower the measured harmonic currents to a level that will meet IEEE 519 standards at the main bus terminals. The combination of PHF and AHF is called a hybrid solution and has been used on many applications.