Over-current protection scheme for SiC power MOSFET DC circuit breaker

The electronic circuit breaker used in DC microgrids are required to work within their safe operating areas bounded by temperature, voltage and current limits. Traditional approach managed to protect these switches through rapid current cut-off operations at over-load or fault situations, but failing to avoid the disturbance induced by transient current surges or noises which are not harmful to the grid operations. Aiming to increase the quality of circuit breaker operations and furthermore improve its reliability, this paper proposed a SiC MOSFET based DC circuit breaker based on the variable time-delay protection scheme. The cutoff operations only take place after proper delay time, which are precisely catered according to the transient thermal properties of SiC devices and the properties of DC loads. The proposed scheme has been implemented with hardware prototype and experimentally verified under different fault situations.

I. Introduction

DC microgrids are used in modern buildings, vessels and vehicles as efficient delivery interconnects between DC energy sources and loads. Similar to AC grids, circuit breakers in DC microgrids carry the function on grid protection. Therefore, these breakers not only do endure grid normal operations and but also be capable of cutting off currents under various fault levels. Solid-state DC circuit breakers made of the modern wide bandgap power semiconductor devices, such as silicon carbide (SiC) and gallium nitride (GaN) MOSFETs can largely enhance the switching performance much better than the mechanical counterparts [1], [2]. These wide bandgap power devices have higher voltage sustainability, higher temperature tolerance and faster switching speed with simple driving requirements [3]. For the voltage level of 400V for the DC microgrids, the use of SiC power devices is a prominent choice for the circuit breaker due to their remarkable performance merits [4], [5].