Distributed Optimal Voltage Control Considering Latency and Asynchronous Communication for Three Phase Unbalanced Distribution Systems

Integration of distributed energy resources (DERs) helps realize sustainability and reduce carbon footprint, but may cause voltage control issues in the distribution power system. The impact is mainly driven by the intermittency and variability of DERs typically connected at the edge. Traditional centralized optimal voltage control lacks scalability, and local voltage controls are not optimal. Distributed algorithms are scalable, robust to failures, and possibly require less communication resources compared to centralized. This paper presents a new online distributed voltage control algorithm with primal-dual updates and auxiliary variables for three-phase unbalanced distribution systems. The phase-specific active and reactive power of participating voltage control agents is regulated considering the power converter operational limits. The algorithm is validated to regulate voltage for both static and dynamic loading conditions for three-phase unbalanced IEEE 13 and 123 bus systems modeled in the OpenDSS. The robustness of the algorithm is validated for delayed asynchronous communication, modeling errors, and measurement noises. Simulation results and convergence analysis show the superior performance of the proposed algorithm.