Design and Analysis of a Cascaded Modular Thyristor-Based DC Circuit Breaker for Medium-Voltage Applications

With the surge of artificial intelligence (AI) workloads, large-scale data centers are rapidly transitioning toward high-capacity direct current (DC) power architectures to enhance conversion efficiency and reduce power losses. However, the ultrafast fault transients and high fault currents inherent to DC systems present stringent requirements for protection devices, which conventional electromechanical circuit breakers cannot satisfy due to their limited response speed and endurance. To address these challenges, this paper proposes a Cascaded Modular Thyristor-Based DC Circuit Breaker (CTDCB) tailored for medium- and high-voltage DC distribution in data center power systems. The proposed topology connects multiple identical modules in series, thereby achieving scalable voltage withstand capability and enhanced energy absorption. Each module incorporates a self-contained commutation circuit with one-shot triggering and no external precharging, offering compact design and improved operational reliability. A saturable inductor is utilized to suppress the thyristor di/dt during turn-on and, upon saturation, to generate a steep commutation current for rapid current zero-crossing and fault interruption. Furthermore, an analog real-time protection unit coordinates module triggering and voltage equalization, ensuring uniform voltage stress and synchronized current interruption across modules. Simulation and analytical results demonstrate that the proposed CTDCB achieves significantly reduced interruption time and improved fault energy absorption compared with conventional solid-state breakers, making it a promising candidate for next-generation AI data center DC power distribution systems.