Two-Stage DC Fault Current Limiter Combining Hybrid Magnetic Materials and Active Flux Coupling Coils

Fault current limiter (FCL) serves as a promising solution for severe fault issues in high-voltage direct current (HVdc) systems. However, the small impedance changing ratio and fault detecting time delay of the existing HVdc system FCL topologies make them have some performance deficiencies. In this article, a two-stage dc FCL (TFCL) was proposed, which has a large impedance changing ratio and automatic fault response characteristics. Fault current can be first restricted by the automatically increased inductance provided by the saturated core FCL module, and then limited by an active precharged capacitor through a flux coupling coil. Hence, the two-stage fault-limiting performance brought by TFCL can be much improved. Magnetic and electric circuit analyses were performed with regard to each different working period. Besides, parameter analysis and performance comparison between different FCLs were conducted in terms of several performance indexes. Finally, electromagnetic simulations, HVdc system simulations, and prototype experiments verified that the proposed TFCL can present much-improved fault-handling capability against the existing current limiting reactor, traditional saturated core FCL, and flux coupling type FCL.