Original ResearchPublished 1 October 2026Voltage support strength-constrained transmission network expansion planning for renewable-integrated grids via deep reinforcement learningJiaming Li · Ke Wang · Yan Li · Xueying Guo · Kanglong Yuan · Haipan Li · Wenyun Luo · Lei ChenFrontiers in Energy Researchdoi 10.3389/fenrg.2026.1869996