Optimization and Control of a Z-Source, Ultrafast Mechanically Switched, High-Efficiency DC Circuit Breaker

Abstract

A novel design of the Z-source circuit breaker topology is presented to minimize on-state losses of the protection device. An ultrafast mechanical switch is proposed to commutate the fault current and improve the controllability of the circuit breaker. Replacing the power thyristor in the Z-source circuit breaker and integrating an advanced control scheme reduces energy losses with a low-resistance mechanical contactor. The proposed design facilitates bidirectional current flow, enhances control capability for distributed energy resources, and improves ride-through capabilities during load transients. Z-source circuit breakers utilize an impedance network to create a forced current zero crossing in the event of a fault, allowing the inline thyristor to isolate the fault from the source through reverse bias. However, full load current flows through the thyristor, resulting in high loss and heat generation. The concept is validated, and a proper control scheme is developed for this circuit breaker through an analytical estimation model of the system dynamics during a fault. Simulation and modeling are performed in power systems computer aided design (PSCAD) and piecewise linear electrical circuit simulation (PLECS). Finally, an experimental laboratory prototype is tested to validate the analytical and simulation models and certify the control logic.