Flexible DC-Traction Power-Supply Systems: Series-Parallel Connected Normally-On SiC JFET-based Medium-Voltage Solid-State Circuit Breaker

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Abstract
Silicon-carbide (SiC) solid-state circuit breakers (SSCBs) are essential components of flexible direct current (DC)-traction systems used in urban-rail transportation because they facilitate rapid and arc-free fault isolation. However, SSCBs using single SiC devices are inadequate for medium-voltage, high-current applications. Therefore, a novel SSCB topology and single-gate drive circuit were proposed, using a series-parallel configuration of normally-on SiC junction field-effect transistors (JFETs). The main switch adopted a three-series and two-parallel connection using six 1.2 kV/63 A normally-on SiC JFETs. The proposed single-gate drive circuit achieved both static and dynamic balancing of voltage and current, among all the SiC JFETs—during short-circuit fault isolation and recovery—and required only a few passive components. The SSCB operating principles during short-circuit and recovery processes were analyzed. A key-parameter optimization method is presented in this paper. Experiments on a 1.5 kV/126 A SSCB prototype demonstrated the performance of the circuit configuration presented. Results showed that the SSCB interrupted a 500 A short-circuit fault (fault resistor was 3 Ω) within ~16 μs, maintaining superior voltage and current uniformity during the entire switching cycle.
Funding Information
  • Natural Science Foundation of Hunan Province (2025JJ50283)

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