Unified Power Flow Solver for Hybrid AC/DC Distribution Networks

Abstract

Hybrid ac/dc distribution grids are gaining popularity due to their potential to conflate the benefits of both ac and dc grids. However, the complex structure of these grids imposes new challenges in power flow (PF) calculations due to multiple ac/dc interconnections, variety of converter operations, and constant dc power loads. This paper proposes a unified PF algorithm incorporating different types of ac/dc and dc/dc converters. The proposed approach is based on the Newton Raphson (NR) algorithm and uses the Modified-Augmented-Nodal-Analysis (MANA) formulation. The proposed formulation can handle arbitrary hybrid ac/dc configurations. The modular structure allows incorporating arbitrary devices and converter controllers. The formulation is built on the summation of line flows and their associated derivatives instead of bus power injections to handle connections with different types of buses equipped with various converters in a straightforward manner. The proposed algorithm is implemented in MATLAB and tested on the modified IEEE 33 bus test system for various configurations. Electromagnetic Transient (EMT) simulations confirmed the accuracy of the proposed method.Another original contribution of the paper is the demonstration of the improved convergence characteristics of MANA based formulation over classical NR formulation through comparisons of conditioning number.