Γ-Z-source DC circuit breaker operation with variable coupling coefficient k

Coupled inductors Γ-Z-source DC circuit breakers are designed to be an automatic, fast, and reliable breaker for many medium DC voltage power systems operating with renewable energy sources. The aim of this work is to analyze and evaluate the performance of the Γ-Z-source DC breaker under different conditions of coupling. In that aspect, the voltage, current and impedance transfer functions are derived in terms of the coupling coefficient between the two inductances in the circuit. The frequency response is also analyzed under different values of coupling coefficient. Results verify that coupling coefficient need to be higher than a void value for the circuit breaker to interrupt current due to a faulty situation but need not be a perfect unity. Also, the void value of coupling coefficient can be changed by varying the turn ratio of the coupled coils in the circuit breaker. Simulation results confirm that as the turn ratio increases the required coupling coefficient drops allowing designers more flexibility in selecting the coupling degree.