A New Efficient Bidirectional T-Source Circuit Breaker for Flexible DC Distribution Networks

The low-voltage dc distribution networks are emerging as a great development trend for their flexible access to photovoltaic energy. However, there is no mature dc circuit breaker to protect dc fault. T-source circuit breakers can quickly and automatically cut off a fault current in a very short time. Compared with the Z-source circuit breakers, the T-source circuit breakers have greater advantages of zero reflected current, common ground, and capability of low-pass filtering. However, as a result of high power loss of semiconductor devices, the transmission efficiency is reduced. Therefore, this article proposes a new efficient bidirectional T-source circuit breaker. The number of semiconductor devices that conduct in steady-state is reduced, and therefore the ON-state loss is reduced by more than 40% compared with the existing bidirectional T-source circuit breakers. The new circuit breaker can be manually turned off by reusing the capacitors. The soft-starting circuit is also integrated into the circuit breaker. Finally, it is verified by simulation and experiment that the new circuit breaker has the capabilities of fault clearing, manual tripping, and soft starting.