To address voltage violation issues in active distribution networks, this paper proposes a reactive power optimal configuration method that considers the dynamic voltage regulation strategy of a unified power quality conditioner (UPQC). First, an adaptive network partitioning model based on reactive power–voltage modularity is developed. This model identifies high-sensitivity regions and determines preferred siting locations for UPQCs. Next, a voltage stability index is derived using a two-bus equivalent decoupled model. The classical holomorphic embedding method is then applied to track the variation in the voltage stability index, with respect to the embedding factor. Based on these results, weak buses are identified as key buses for evaluating the effectiveness of voltage control measures. Subsequently, a bi-level optimisation model that integrates planning and operation is formulated by incorporating the dynamic voltage regulation strategy of the UPQC. The model aims to minimise the equivalent annual total cost of the deployment scheme while reducing bus voltage deviations, thereby enabling proactive mitigation of voltage violations in active distribution networks. Finally, case studies conducted on an extended IEEE-33 bus power system and real-world distribution networks demonstrate that the proposed UPQC optimal configuration method effectively alleviates voltage violation problems.