Abstract:Since distributed generation ( DG) generates distributed power system harmonic problem when connected with the grid through power electronic devices，a distributed active filter system (DAFS) is put forward to suppress harmonic. Multiple active filters (APF) are parallelly connected with the grid containing multiple harmonic sources through optimal allocation，so as to achieve lowest total harmonic distortion (THD). In order to ensure long-term stable operation of the APFs，droop control is introduced for improvement. Therefore，division of load power and inhibition of circulation can be realized，and line voltage distortion rate can be maintained at lower levels. Finally，the simulation result shows the correctness and validity of the theory.