A 4kV/100A DC Solid-State Circuit Breaker with Soft Turn-off Operation

This paper deals with design and implementation of a practical 4 kV/100 A solid-state circuit breaker (SSCB) for medium voltage dc (MVDC) applications. Transient current commutation is applied to the main switch to achieve a soft turn-off during dc current interruption. The presented topology eliminates the transient power and energy on the main switch, leading to more reliability. A Boost converter-based resonant circuit is employed as the auxiliary branch to generate a countercurrent pulse to oppose the dc current in the main switch. The injected pulse current is adjustable in terms of duration and amplitude. Two capacitive couplers connect resonant circuits to the main switch and play a key role in preventing short circuit failures in the auxiliary branch. To verify the SSCB, two sets of experiments are conducted including load and short circuit interruptions under 4 kV dc bus. Experiments reveal 77 µs reaction time interval in interrupting 100 A dc current, where the peak of the countercurrent pulse reaches 106 A. The main switch presents 42% voltage utilization rate, and it experiences 5.36 kV voltage peak overshoot; meanwhile, its power shock reduces to zero. The SSCB achieves 99.97% efficiency for the rated current of 100 A.