Novel Bidirectional O-Z-Source Circuit Breaker for DC Microgrid Protection

Abstract

DC microgrids that feature a simple and efficient integration with renewable energy sources and energy storage elements have drawn increasing attention in industrial applications. In this article, a bidirectional Z-source circuit breaker with an O-shaped impedance network (abbreviated as O-Z-source circuit breaker) is proposed to guarantee the reliable operation of dc microgrids. By a simplified structure, the O-Z-source circuit breaker allows bidirectional power flow with fewer components compared with conventional Z-source circuit breakers. Increased operating power efficiency can also be obtained from the novel topology. Based on detailed mathematical models, design equations are derived for sizing the components in the O-Z-source circuit breaker. Moreover, a new concept of equivalent capacitance that is useful for estimating the minimum detectable fault ramp rate for Z-source circuit breakers is presented. A discussion over snubber circuits of the proposed breaker is also included. Finally, a laboratory prototype has been built to verify the analysis and design the O-Z-source circuit breaker.