Configuring distributed synchronous condensers in renewable energy collector stations is a viable approach to mitigating transient overvoltage at grid connection points. Traditional distributed synchronous condenser’s location and capacity selection strategies are mostly based on fixed output scenarios of renewable energy, ignoring the randomness of wind and solar power output at each node, making it difficult to ensure the effectiveness and adaptability of the strategy. In view of this, the maximum grid connected power of renewable energy based on confidence intervals was estimated. A multiple renewable energy stations short circuit ratio index that takes into account the randomness of renewable energy is proposed to quantitatively evaluate the voltage support strength of each node in the power grid. Based on this, a distributed synchronous condensers location and capacity determination strategy is formulated. Simulation results demonstrate that the proposed strategy can accurately identify nodes with weaker voltage support capabilities under actual fluctuations of renewable energy outputs. Compared to conventional strategies, it proves more effective in suppressing transient overvoltage in the sending-end system, offering technical support for large-scale renewable energy integration into power grids.