There are a series of problems such as large load fluctuations and poor power quality caused by the grid connection of large-capacity shore power systems to the grid operation. A cost-effective compensation scheme is proposed to improve the stability and safety of grid operation. The stability of the power grid after large-capacity shore power access, including the volatility of shore power, the impact on the reactive power distribution of the power grid, and the influence of system voltage, network loss and power flow distribution, is studied. On this basis, the output of a large-capacity shore power model is established and the operational status of the distribution network with ship load access is simulated. The simulation results show that the scheme can improve the security and power quality of the shore power access system, and provide a reference for promoting the rapid development of shore power and the construction of green ports. This work is supported by National Natural Science Foundation of China (No. 51507157).