Solid-State DC Circuit Breaker Based on HTS Fault Current Limiter and SiC MOSFET Modules

An improvement of the conventional solid state dc breaker (SSDCB) is developed for shipboard medium-voltage dc (MVDC) system protection. By combining a high temperature superconducting fault current limiter (HTS-FCL) with a SSDCB based on Slicon Carbide (SiC) MOSFETs, the efficiency of the SSDCB portion is improved while the number of switching devices necessary is significantly reduced with the assistance of the HTS-FCL. The natural current limiting properties of HTS cables are leveraged such that the HTS-FCL has negligible insertion losses and passive fault limitation. In normal operation, the nominal load current flows through the superconductive HTS-FCL and SiC MOSFETs with low conduction losses. During a fault, the HTS-FCL becomes a significant resistance which limits the peak magnitude of fault current. This reduces the number of SiC devices in the SSDCB which then interrupts the fault. After interruption, a metal-oxide varistor device clamps the transient overvoltage which limits voltage stress and excessive switching losses. Simulation results are provided to verify the main functionality of the breaker in a 20 kV shipboard MVDC power system.