Influence of Inrush Current of Converter Transformer on High-voltage DC System Based on Unbalanced Residual Magnetism

In high-voltage direct current (HVDC) transmission systems, the inrush current of the converter transformer can have severe impacts on the system. This paper establishes a model of an ±800kV DC transmission system based on the imbalanced remanence characteristics of the converter transformer. It calculates and analyzes the effects of inrush current on the primary side of the converter transformer and the AC bus. A comparative analysis is conducted between the inrush current under imbalanced and balanced residual magnetism, examining the inrush current characteristics through the content of the inrush current and the proportion of total harmonics under different types and levels of remanence. Finally, the paper compares and analyzes the suppression effects of two closing strategies on the inrush current caused by remanence. The research presented in this paper provides certain guiding significance for comprehensively understanding the impact of residual magnetism in the converter transformer core on inrush current, as well as the impact of inrush current on AC systems.