Design of a Novel Dual-Mode Γ-Source Circuit Breaker with Commanded Interruption Strategy

With the continuous growth of global clean energy demand, DC microgrids have been widely used due to their efficient and reliable power supply characteristics. However, the characteristic that its fault current has no natural zero-crossing point makes fault isolation challenging, and the traditional Γ-source circuit breaker (ΓSCB) is difficult to meet the increasingly higher response speed requirements. In this paper, a dual-mode Γ-source circuit breaker (DM-ΓSCB) topology based on the capacitor series-parallel reconstruction technology is proposed. By anti-parallelly connecting two capacitor-resistor series paths in the capacitor branch and using the auxiliary thyristor to control its conduction state, the dual functions of fault interruption and controlled interruption are realized. At the same time, an analog protection unit integrating overcurrent, current rise rate and inverse time delay protection is designed, which can achieve microsecond-level fast interruption. The simulation results show that the proposed topology can quickly force the main thyristor current to cross zero under different fault conditions and achieve reliable fault isolation.