Unified implicit Z-bus power flow solver for hybrid AC/DC distribution networks

Abstract

In the future power system, characterized by the massive integration of distributed energy resources (DERs), the AC/DC hybrid network represents a highly promising technology that will play a crucial role at power distribution levels. As essential analytical tools for AC/DC distribution networks, Newton-Raphson (N-R) based unified AC/DC power flow methods have been developed and widely used. However, the N-R method encounters challenges such as divergence, multiple solutions, and high sensitivity to initial values when solving power flow problems in distribution networks, particularly in radial and meshed distribution network topologies, especially under conditions of high R/X ratios or heavy loads. To address these issues, this paper presents a novel unified AC/DC power flow algorithm based on the implicit Z-bus (IZB) method. Considering the various combinations of nodes and feeders in AC/DC hybrid distribution networks, a unified power flow solver based on an IZB iterative mapping is proposed. Numerical tests validate the proposed solver, demonstrating its superior capability to achieve high computational efficiency while reliably converging to feasible solutions without being influenced by the choice of high R/X ratios, initial values, and heavy loads.