A Z-Source Ac Circuit Breaker

This paper presents an ac version of the popular dc Z-source circuit breaker. The Z-source breaker is distinctive in that it has a negative current transfer characteristic. That is, an increase in output current on a short time scale will cause a sudden decrease in input current. Therefore, the Z-source breaker can react to a fault in microseconds which is also valuable in some ac applications. After introducing the schematic and operation of an ac Z-source circuit breaker, the SCR gating method is described. This turns out to be more involved than for the dc circuit breaker because of gating requirements for additional SCRs in the circuit. Detailed simulation validates the proposed ac circuit breaker over four quadrants of positive and negative voltage and current at the time of the fault.