This paper mainly introduces an active power electronic compensation device of a power distribution network applied to the low-voltage power distribution network three-phase four-wire system and analyzes the fundamental principles of direct detection on the fundamental wave active current components. After the simulation in Matlab/Simulink environment by using the compensation characteristics of the power distribution network active compensation device in this control mode in the harmonic and reactive aspects, especially on the condition of unbalanced load of the power distribution station area, this paper proves the feasibility of the detection control method of the active compensation device and the good compensation characteristic in the condition of unbalanced three-phase load. Lastly, this paper proves the validity of the theory on the condition of reactive compensation power distribution station area and unbalanced three-phase currents.