Such issues affecting power quality as harmonic current

load unbalance current

neutral current and low power factor etc are caused due to the increase of non-linear

unbalance load and reactive load in the distribution power grid

the shunt active power filter is normally used to achieve elimination of harmonic

reactive power compensation load unbalance current and neutral current. In the field of harmonic detection of active power filter

the shortcoming of the traditional theoretical method based on transient reactive power is analyzed

new harmonic detection method is proposed and the moving average filter（MAF） is used to replace low pass filter（LPF）for the extraction of DC component

which overcomes such defects as weak real time and dynamic of traditional detection method due to the low pass filter and

at the same time

simplifies model structure. The simulation and experimental platform is set up. It is shown by the simulation and experimental result that the new detection method has perfect detection result and superiority.