With the large number of distributed photovoltaics(PVs)dispersedly accessed in middle-low voltage distribution network

power quality problems of distribution network are becoming increasingly conspicuous

making the limit peak capacity of distributed PV accessed in distribution network the focus of attention. Following a study of the influence factors and the influence level of distributed PV on the power quality

an optimal calculation model based on the current injection method is proposed to meet the need of limits of power quality. The model is constrained by power quality indices of multiple national standards

with the peak value of the distributed generator accessed given for both new and expanded cases of limit peak capacity. The validity and practicability of the model are verified by the test results of the IEEE 33-bus system and actual LCX system. For the features of typical 10 kV line

the safety limits of distributed PV with power quality constraints are given according to different line types in different regions. The results can provide reference for the power supply enterprise in checking the grid-connected application of distributed PVs. This work is supported by National Natural Science Foundation of China(No. 51407036)and National Basic Research Program of China(973 Program)(No. 2013CB228205).