Research On The 270V DC Solid State Circuit Breaker Based On SiC MOSFET

With the rapid development of economy,the energy demand is increasing,at the same time,the requirement for power quality is getting higher and higher.DC power supply is expected to become an important form of future energy transmission for its low loss and high reliability.The circuit breaker is a key device in the power transmission and distribution systems,which can directly affect the stability and reliability of system.The traditional mechanical circuit breaker is difficult to meet the requirement of the DC protection system,and the DC solid state circuit breaker based on silicon devices has high loss and low junction temperature,which greatly limit the development and application of solid state circuit breakers.Compared to silicon device,the silicon carbide device has the advantages of small on-resistance,fast switching speed and high thermal conductivity,which provides favorable conditions for the development of DC solid-state circuit breakers,and is gradually getting attention of researchers at home and abroad.The SiC-based power devices should not be simply considered as high voltage power devices,for their different material properties.In order to ensure reliable operation of silicon carbide power devices and use its characteristic advantages,DC solid state circuit breaker based on silicon carbide power devices can get better performance,the dynamic,static and thermal characteristics of silicon and silicon carbide MOSFETs are analysed in this paper,and the influence of its parameters on the electrical characteristics is studied in detail.Then,on-resistance test circuit and double pulse dynamic test circuit are designed and built.Compared to silicon MOSFET,silicon carbide MOSFET has smaller die area,higher current density,thus,the weaker short-circuit ability and shorter short-circuit withstand time,which brings great challenges to the design of short-circuit protection for the silicon carbide MOSFET.In this paper,the short circuit characteristics of silicon carbide MOSFET are studied and mechanism of short-circuit current is analyzed in detail.Then,the short circuit test prototype is set up and the influence of circuit parameters on the short circuit characteristics of silicon carbide MOSFET is tested and compared.The key factors of short circuit characteristics is revealed,which provides some guidance for the design of short circuit protection circuit.Finally,a soft turn-off circuit,which can both suppresses the short-circuit peak current and reduces the over-voltage,is presented.The prototype of 270 V DC solid state circuit breaker based on silicon carbide MOSFET is designed and built.Different methods of clamping gate voltage tested and compared.Meanwhile,the dynamic response of DC solid state circuit breaker under two short circuit faults is tested,verifying the validity and reliability of the prototype.