To better carry out harmonic

negative and zero sequence current compensation and control

harmonic current detection method for active power filter（APF） was studied in-depth

and a new method based on adaptive principle for FBD harmonic current detection was proposed in this paper. Firstly

the principles of the traditional FBD algorithm for harmonic current detection were analyzed. Due to the limit from the low-pass filter

its detection accuracy and speed of harmonic currents were affected. Then

with the similarity for the structures of the FBD and the adaptive harmonic current detection algorithm

the adaptive compensation adjusting kernel（LMS）was proposed to substitute the low-pass filter in FBD detection.Finally

the improved FBD algorithm and the traditional FBD algorithm were applied to APF for engineering tests. The comparison results showed the feasibility and effectiveness in APF of the proposed algorithm.