Distributed multi-area load flow for multi-microgrid systems

Due to deregulation of distribution network investment businesses, geographically divided microgrids may be owned and operated by different entities. In this study, distributed multi-area load flow (LF) calculation method that can preserve the operational independence of each entity is necessary. However, conventional fixed-point iteration-based distributed LF (DLF) algorithm may encounter convergence problems in active distribution networks integrated with high penetration of distributed generators (DGs). In this work, the authors propose a more general and novel DLF algorithm to better accommodate the integration of DGs. In this algorithm, the original non-convex LF model for multi-microgrid systems is convexified into a second-order conic LF problem and then decomposed into a regional LF subproblem using a modified alternating direction method of multipliers (ADMM). The conventional ADMM is enhanced by asymmetric decomposition and partial boundary penalty relaxation with regard to the specific LF problem structure to accelerate the convergence procedure. Numerical tests on an IEEE 69-bus distribution system and a 345-bus system show that the proposed method outperforms the fixed-point iteration-based DLF method.