A Backward-Forward Sweep Based Power Flow Algorithm for Generalized AC-DC Distribution Network with Distributed Generations

Abstract

Developing a power flow (PF) methodology for the AC-DC distribution network is complex but important, especially due to the involvement of power converters. In this work, a Backward-Forward Sweep (BFS) approach developed based on graph theory and matrix algebra is proposed for solving the PF for both the radial and mesh configured AC-DC distribution networks with distributed energy resources (DERs). For this purpose, first, the per-unit current, voltage, and power model of the 3- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\phi$</tex-math></inline-formula> pulse width modulated (PWM) rectifier, 3- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\phi$</tex-math></inline-formula> PWM inverter, and DC/DC power converter have been developed. Then, a generalized sensitivity matrix has been developed for computing the loop breakpoint, PV breakpoint, and V <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{dc}$</tex-math></inline-formula> breakpoint injections simultaneously allowing the approach to work for both mesh and radial networks with DERs modeled as PQ, P, PV, and V <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{dc}$</tex-math></inline-formula> buses. The major benefits of the proposed algorithm are that it can incorporate various functional/control modes of the aforementioned converters. The feasibility of the proposed power flow algorithm has been explored on AC-DC distribution test networks. The test results show that the approach is feasible and precise.