Abstract: Due to the large difference in the effective value of current between inverters,the grid connected under the traditional distributed roof photovoltaic access is prone to imbalance. To this end,a grid connected power balance control method under the distributed roof photovoltaic access is proposed. According to the principle of distributed roof photovoltaic access and grid connection,the structural model is established,and the mathematical model of photovoltaic array and inverter is determined. The vector diagram is used to express the change of grid connected power balance of distributed roof photovoltaic access,and the vector relationship between grid connected zero sequence voltage vector and three-phase output voltage of inverter is determined;The inverter three-phase rated power,three-phase power error,amplitude and phase of zero sequence component are calculated,and the inverter phase-tophase power control block diagram superimposed by zero sequence component is designed to control the inverter phaseto-phase power balance. The simulation parameters are determined and the experimental working conditions are set. The simulation control results are as follows: under the condition of working Condition 1 with no serious grid connected power imbalance,the difference of current effective value of the research method in this paper is ± 0.01 A,which is less than that of the other two comparison systems;Under the condition of Condition 2 with serious grid connected power imbalance,the difference of current effective value of the research method in this paper is ± 0.02 A,which is much smaller than the other two comparison systems. The control performance of the research method in this paper is better than the other two comparison methods,and it has great application value.