Adaptive ADMM-based optimal power flow for distribution systems via dynamic penalty strategy

To mitigate voltage fluctuations caused by intermittent distributed generation (DG), this paper proposes a reactive power optimization strategy based on an Improved Alternating Direction Method of Multipliers (I-ADMM). The model coordinates switchable capacitor banks (SCBs), on-load tap changers (OLTCs), and the reactive power capabilities of DGs to balance voltage quality and active power losses. Simulation results on the IEEE 33-bus system show that the proposed I-ADMM reduces total voltage deviation by 18.71% and 25.94%, and decreases branch losses by 9.51% and 10.67% compared with T-ADMM and C-OPF, respectively. In addition, a multi-period validation under time-varying DG and load conditions shows that the proposed method maintains effective performance across representative operating periods while preserving voltage security. Additional validation on a modified IEEE 69-bus system further confirms the scalability of the proposed method. These results demonstrate improved computational efficiency and the effectiveness of the proposed adaptive penalty strategy for distributed OPF under representative time-varying operating conditions.