The structure of the distribution network system in distributed grids is complex, and with the large-scale integration of power electronic devices, the issue of serious harmonics is becoming increasingly prominent, thereby affecting the power quality of the grid and severely threatening the normal operation of sensitive equipment in the distribution network. This paper proposes a unified control strategy for PV grid-connected generation and active power filters (APF). Currently, APF devices are mainly used in industrial three-phase high-power systems to eliminate harmonics, but they are costly and have a single function. Therefore, this paper, based on the harmonic current detection principle in the instantaneous reactive power theory, proposes a unified control strategy for PV grid-connected generation and APFs. Finally, the proposed reactive current and harmonic current detection method and the design method of the current loop and voltage loop controllers are validated through simulation and experiments, proving their correctness and feasibility.