Integrated Damping Solid-State Circuit Breaker for Inrush Current Suppression in DC Microgrids with Reconfigurable Voltage Sources

Abstract

Solid-state circuit breakers (SSCBs) provide fast, arcless fault clearance, resulting in a longer service life compared to mechanical circuit breakers (MCBs) in DC grids. Black-start operations refers to the process of restarting a grid without an external power source, usually using the system’s internal energy storage system (ESS). SSCBs can be damaged by inrush currents during black-start operations in DC microgrids because power semiconductors have limited current-handling capability. To mitigate the inrush current during black-start operation, this study presents a bidirectional integrated damping solid-state circuit breaker (ID-SSCB) topology for DC microgrids designed for shipboard and aircraft electrical systems. The topology augments the main semiconductor branch with a controlled damping/auxiliary semiconductor branch, which (i) suppresses initial inrush currents; (ii) reverts to the low-loss steady-state branch; or (iii) decreases black-start times for equivalent current stress through the use of a current-damping strategy for a stepwise reconfigurable voltage source introduced by the proposed algorithm. An additional snubber and metal-oxide varistor (MOV) branch limit transient overvoltage in the main branch during fault current interruption by absorbing the residual energy. This study analyzes the design criteria for the proposed SSCB topology and the current-damping strategy. A laboratory prototype is developed to corroborate the analysis, demonstrating reduced inrush current peaks and charging times for equivalent current stress. The proposed approach provides a simple method for managing current stress and black-start times in DC microgrids.