Power balance is the key to the security of power system operation. It is a great challenge for the high proportion of renewable energy power systems in the future. The increasing capacity ratio of photovoltaic power station construction and the change of photovoltaic station output power leads to the problems of obstructed renewable energy consumption and increased risk of power balance. In this paper, the capacity ratio of photovoltaic development in the future is considered. Then, the probability of satisfying the simultaneity rate constraint is analyzed and solved based on the historical operation data. The warning index of the transmission line transmission power between the regional power grids is proposed. The early warning of the regional power grid structure and power balance caused by future load or renewable energy development is given. The capacity ratio of photovoltaic development is analyzed based on the simultaneity rate deviation index. Finally, a provincial regional power grid is used to verify the effectiveness and adaptability of the proposed method, which is conducive to improving the accuracy of power balance analysis when the installed photovoltaic capacity of the regional power grid increases.