A study on the comparison of two harmonics detection methods of three-phase four-wire system

Active power filter is a kind of device used for harmonics current detecting and reactive power compensation of three-phase power network. The compensating characters of active power filter depend on precision and real-time of harmonics and reactive power current detection. In this paper, instantaneous reactive power theory of three-phase four-wire system is introduced firstly, and the principle of p-q-o and i_p-i_q-i_o harmonics detection method is described. The steady-state and dynamic respond performance of two methods is proved is good, through theory analysis and the comprehensive comparison of two methods of steady-state and dynamic respond performance, or under the case of source voltage distorted, and the neutral-line current was eliminated well. But when source voltages are distorted, i_p-i_q-i_o method can precisely detect harmonics current, but p-q-o method has apparent error.