Force Turn-off Method of SCR for UPS

In this paper, developing a novel force turn-off method of silicon controlled rectifier (SCR) device. SCR is mainly used as a component of the UPS to be inserted into the static transfer switch (STS). Although SCR can withstand penetrating short-circuit current, it needs to have the ability to quickly cut off the fault current when an accident occurs. The current protection curve is used for uninterruptible power system (UPS) protection coordination and other problems. When an accident occurs, the proposed method can turn-off in a short time. A bypass STS for the online UPS by using SCR is proposed. The design procedure and analysis are presented in detail. The total shutdown time of SCR is less than 250$\mu$s, which is much shorter than the conventional shutdown method. The circuit also uses over-current protection. SIMPLIS$^{\mathbf{TM}}$ software is used to simulate the topologies, after which a mathematical analysis is provided. For demonstration, the proposed circuit is implemented to verify the feasibility.