Abstract: Under the background of the coordinated development of“source-grid-load-storage integration”,with the development of power electronics technology,issues such as voltage fluctuations and harmonic distortion caused by photovoltaic grid-connection have further emerged,so it is important to clarify the mechanism of power quality issues in distributed photovoltaic grid-connected systems to maintain the economic and stable operation of distribution systems. This paper explores the mechanism of various typical power quality problems in photovoltaic grid-connected systems and introduces the structural characteristics and operating principles of typical photovoltaic grid-connected systems; the influence of photovoltaic grid connection on voltage deviation and power factor is analyzed according to the principle. In addition,the resonant risk and harmonic distortion caused by distributed photovoltaic are introduced by analyzing the principle and comparing the simulation data. Finally,based on the measured data of the low-voltage photovoltaic station area and simulation examples, the influence of distributed photovoltaic grid connection on power quality indicators such as voltage deviation, voltage fluctuation, and harmonic voltage is analyzed. The results show that grid-connected PV can cause power quality problems such as voltage fluctuations,resonance,harmonics,etc. Therefore,while promoting grid-connected PV, attention should be paid not only to power quality constraints,but also to absorption and consumption issues brought about by large-scale grid-connected PV.