Abstract: With the large-scale integration of photovoltaic power generation, the grid-connected operation of clustered PV power stations poses significant challenges to reactive power and voltage management in power grids. Existing automatic voltage control (AVC) modes have limitations when handling complex multi-station interactions. Based on operational data from an existing clustered photovoltaic power stations in China, this paper clearly defines abnormal phenomena such as reactive power output imbalance and internal reactive power circulation within the cluster. Mechanistic analysis from two dimensions—network topology and AVC mode—identifies reactive power-voltage coupling and differences in regulation rates as the primary causes. Building upon this, a novel calculation method for reactive power allocation in clustered photovoltaic power stations is proposed. This method comprehensively considers electrical distance, sensitivity, voltage regulation coupling, and response speed, while establishing quantitative evaluation indexes. Simulation results from case study demonstrate that the proposed method significantly improves the balance of reactive power output allocation within the photovoltaic power station cluster, and can effectively suppress or eliminate reactive power circulating within the cluster. These findings and suggestions provide valuable theoretical foundations and practical references for coordinated reactive power and voltage regulation in large-scale renewable energy bases.