Research on magnetically saturated bridge arm coupled reactor in MMC-HVDC systems based on nanocrystalline amorphous materials

The Modular Multilevel Converter-Based High Voltage Direct Current (MMC-HVDC) system relies critically on bridge arm reactors to interconnect AC and DC systems and limit fault currents. However, conventional air core reactors and silicon steel-based magnetically saturated coupled reactors face limitations in adaptive inductance regulation, fault current suppression, and dynamic response. To address these challenges, this study proposes a novel NMAR design incorporating a nanocrystalline amorphous alloy core for the key working column. This material exhibits higher permeability in the desaturation region, a steeper B–H curve knee point, and lower saturation flux density compared to conventional silicon steel. These characteristics enable rapid desaturation under fault conditions and increase the inductance value during faults, significantly enhancing the current-limiting performance while maintaining low inductance during steady state operation. The proposed reactor offers greater fault current suppression capability, demonstrating strong potential for enhancing the safety and stability of MMC-HVDC systems.