Study on the Influence of Converter Transformer Magnetizing Inrush Current on the Low-order AC Filter

The converter transformer magnetizing inrush current issue affects the safe and stable operation of the HVDC system. The characteristics of magnetizing inrush current are analyzed based on actual HVDC project faults. The important factors affecting the magnetizing inrush current are analyzed from three aspects: closing angle, residual magnetism and AC system characteristics. Aiming at the weak AC system, the mechanism of the magnetizing inrush current affecting to the low-order AC filter of the converter station is studied. The low-order harmonic transmission process between the AC system, AC filter, converter transformer and the DC system is analyzed. Base on the actual HVDC project, the energy requirements of the low-order AC filter resistors are analyzed under the different AC system operation mode and AC Filter combination. The mechanism of magnetizing inrush current on low-order filters under weak AC system is studied, which provides guidance for HVDC system design.