Study on Defect Characterization Parameters of Anode Saturable Reactors for HVDC Converter Valves

To address the issues of temperature rise accumulation, structural vibration, and air gap degradation that occur during the long-term operation of Anode Saturable Reactors used in high-voltage direct-current (HVDC) converter valves, electromagnetic-structural and electromagnetic-thermal multi-physics coupling analysis models were established using COMSOL Multiphysics software. The monitorable quantities capable of characterizing defects in Anode Saturable Reactors were systematically investigated from three aspects: vibration signals, thermal signals, and electrical signals. First, a one-way electromagnetic-structural coupling vibration model was established to analyze the vibration characteristics under normal operation, loose core conditions, and polyurethane hardening conditions. Second, an electromagnetic-thermal coupling model was established to compare the core loss and temperature rise distribution between the defect-free condition and the condition with reduced air gap defects. Finally, the effects of air gap reduction on electrical parameters such as unsaturated inductance and frequency sweep impedance were analyzed. The results indicate that the dual-peak characteristics and residual vibration of vibration signals can reflect the looseness of the iron core, while thermal aging of the polyurethane filling material further weakens the system’s damping capacity, intensifying vibration impact on the core and structural components. A reduction in air gap leads to an increase in local core loss of approximately 47.9%, giving rise to local hot spots. For the shell-type ASR investigated in this study, the temperature rise of the reactor casing remains almost unchanged. The unsaturated inductance and the impedance value near 10 kHz are highly sensitive to air gap variations and can serve as effective feature quantities for online monitoring.