Protection circuit design for AC solid-state circuit breakers under inductive load conditions

With the increasing penetration of high-power inductive loads in AC power systems, the AC solid-state circuit breaker (SSCB) is being subjected to severe overvoltage stress and fault energy during short-circuit current interruptions. Existing protection circuit schemes struggle to provide reliable protection for the SSCB. To address this issue, this paper proposes a protection circuit topology that integrates an energy absorption snubber with active bypass. During short-circuit faults, the coordinated operation between the TVS-RCD energy absorption snubber circuit and the active bypass circuit employing common-source MOSFETs enables rapid fault interruption. This approach offers advantages including voltage overshoot suppression, fast surge energy absorption, and active fault isolation. This paper presents a detailed analysis of the proposed protection circuit topology and its operating modes, providing a computational basis for parameter design. Key parameters are determined through simulation studies, which evaluate the circuit performance under various short-circuit fault conditions. The results demonstrate that the proposed protection circuit effectively suppresses overvoltage stress on the AC SSCB, eliminates voltage oscillations, and achieves rapid decay of fault currents. Finally, 380 V AC SSCB prototype was built, and the effectiveness of the proposed circuit topology was verified in terms of voltage clamping, energy absorption, and quick fault current clearing capability.