Bidirectional Q-Z-Source DC Circuit Breaker

In this article, a novel Z-source dc circuit breaker topology with a Q-shaped impedance network (Q-Z-source circuit breaker) is presented. The new topology has a better performance and is more resilient properties than those of the recently published O-Z-source circuit breaker. The new Q-Z topology provides bidirectional protection but only requires one semiconductor switch in its current path during normal operation, leading to a simpler and smaller physical structure and a lower conduction penalty. It also drastically improves the sensitivity issue on the magnetic coupling coefficient that manifests in the existing O-Z-source circuit breaker. In a realistic, practical application with a nonideal magnetic coupling coefficient, the new topology requires a smaller capacitance that can be translated into lower weight and/or lower cost. Detailed mathematical models are built to analyze and compare the short-circuit fault responses of a variable coupling coefficient. The bidirectional snubber circuit and its connection to the Q-Z topology are discussed for achieving faster fault clearing. Finally, a prototype is built in the laboratory to verify the theoretical analysis and improved performance of the proposed bidirectional Q-Z-source dc circuit breaker.