Multi-timescale voltage optimization and control for distribution networks based on regional priority evaluation and deep reinforcement learning

Abstract With the increasing penetration of distributed photovoltaic (PV) generation, energy storage systems, and other flexible resources in distribution networks, conventional voltage regulation methods struggle to address both overvoltage and undervoltage violations and to coordinate heterogeneous devices operating at different timescales. Existing region-based multi-agent control methods typically treat partitioned regions as homogeneous decision-making units and lack an explicit mechanism to characterize spatiotemporal variations in regional regulation capability and available flexibility. To address these limitations, this paper proposes a multi-timescale voltage optimization and control method for distribution networks based on regional priority evaluation and deep reinforcement learning. First, a coordinated voltage regulation architecture spanning long and short timescales is established. At the long timescale, a double deep Q-network (DDQN) is employed to centrally schedule discrete voltage regulation devices from a system-wide perspective. At the short timescale, a comprehensive regional voltage regulation evaluation index is introduced to quantify the regulation capability and potential of each region and thereby determine its regulation priority. A priority-aware state feature encoding (PASFE) module equipped with a learnable gating mechanism then adaptively fuses regional physical information with coordination information broadcast by the upper-level controller. The resulting priority-aware representations are incorporated into the regional actor and centralized critic networks, enabling the multi-agent algorithm to perform fine-grained regulation of individual continuously adjustable devices. Case studies on the IEEE 33-bus and 141-bus systems demonstrate that the proposed method effectively eliminates bus-voltage violations and outperforms the benchmark strategies in mitigating voltage deviations and reducing network losses, thereby confirming the effectiveness of regional-priority guidance in enhancing coordinated multi-timescale voltage regulation.