The impact of source and fault impedance on post-fault response of z-source circuit breakers

The Z-Source circuit breaker is a type of DC power electronic circuit breaker, which is able to autonomously isolate faults. It uses a circuit of passive components to autonomously commutate the main conducting switch (a thyristor) off during a fault. In order for the ZCB to operate correctly, the thyristor must remain reverse-biased for a defined time period when a fault occurs, i.e., the minimum turn-off constraint must be met. External fault and source impedances modify the time period that the thyristor remains reverse biased, which in turn impacts the fault conditions for which operation is autonomous. In this paper, this effect is investigated analytically through simulation and through experimentation on a hardware prototype.