Distributed Reactive Power Optimization for Flexible Distribution Networks With Successive Relaxation Iteration Method

The flexible soft open point (SOP) connected to active distribution networks (ADNs) offers a promising manner of improving voltage and VAR control (VVC) by providing flexible power regulation. Due to the expansion of interconnective networks, the centralized optimization method has recently faced various challenges. This paper thus proposes a novel distributed coordinated reactive power optimization strategy for SOP-based multiregional ADNs based on local model decoupling and iterative interactions. By applying the alternating direction method of multipliers (ADMM), the centralized VVC optimization problem is divided into several subproblems, allowing each area to optimize its local subproblem in a fully distributed manner. Multiple resources are thereby coordinated by the VVC, including both discrete and continuous devices. To ensure computability of both integer and non-convex problems, the relaxation iteration and successive linear approximation methods are nested to the ADMM framework, within this approach to allow ready solution to the distributed VVC optimization problem to be generated using a relaxation iterative algorithm, which significantly improves algorithm convergence and computational efficiency. The effectiveness of the proposed method is demonstrated in this work using a modified IEEE standard interconnection system.