PNNL

Abstract

This paper presents a sequential power flow algorithm designed for multi-frequency power systems integrating high-voltage alternating current (HVac), high-voltage direct current (HVdc), and low-frequency HVac (LF-HVac) networks. The detailed modeling of LF-HVac systems is introduced by incorporating low-frequency transmission line parameters and the operating modes of backto- back (BTB) converters, which enable the connection of asynchronous power systems. The study develops a comprehensive power flow model that accounts for converter operational losses, slack buses in each grid, and the components of the BTB converter, which can be extended to an arbitrary number of grids, tie-lines, and converters. To enhance computational efficiency, the proposed method leverages a dynamic acceleration factor adjustment and parallel computing techniques. A case study validates the effectiveness of the algorithm in large-scale power systems, demonstrating improved convergence speed, making it a feasible solution for multi-frequency power flow analysis. The power flow results provide insights into power losses from tie-lines, including transmission line losses and converter losses. The findings indicate that the LF-HVac system incurs power losses comparable to those of HVdc transmission lines. Keywords: AC/