Experimental investigation of the operation characteristics of 3-phase 3-wire active power filter

The conventional passive filtering has been outdated since it detune with age and the performance of passive filters is affected by the grid impedance, which may cause resonance problems. Active power filters (APFs) are attractive solutions to solve harmonics-related power quality problems due to the development of power semiconductors, control theory and digital signal processors (DSP), and they have become the first choice for power quality solutions. This paper systematically investigated 3-phase 3-wire active filter in 3-phase 3-wire and 3-phase 4-wire systems, and both the balanced and unbalanced situations are considered. It was found by various experiments, that 3-phase 3-wire active filter works quite well in 3-phase 3-wire system, however, its performance in 3-phase 4-wire system is unsatisfactory, and it may even inject unwanted harmonics to the grid under certain situations, which deteriorates power quality at the point of common coupling (PCC).