Design And Optimization Of Solid State DC Circuit Breaker Based On Gate Controlled Thyristor

Since DC distribution system features a higher energy efficiency and reliability in some emerging application fields such as micro-grid based on distributed generation and DC data center,more and more researches in recent years have been focusing on the critical issues including fault protection concerned with DC system applications.Compared with AC system,DC distribution system requires a faster and more reliable circuit breaker due to the lack of natural zero voltage cross point and the limitation of short-circuit capability of semiconductor devices in power converters.The commonly used mechanical circuit breaker(MCB)based on thermoelectrics or electromagnetics mechanism suffers from a long response time and poor reliability induced by the arc generated in the fault interruption process,which cannot meet the fault protection requirement of DC system.Compared with MCB,solid state circuit breaker(SSCB)based on power semiconductor devices possesses an ultra-short response time as well as a long-term reliability,which is suitable for the protection of DC system.However,due to the limitation of power semiconductor devices inside,SSCB suffers from a high energy loss and poor fault current interruption capability.To address the mentioned problems,a DC SSCB based on cathode-short MOS-controlled thyristor(CS-MCT)is proposed in this work.Specifically,a prototype of a 400 V DC SSCB is designed with a low loss CS-MCT combined with a current commutation circuit and a current sensing and controlling circuit made up of a hall current sensor and a voltage comparator,and electrical behavior of the SSCB is characterized via mixed-mode simulation as well as experimental measurements.Also,the triggering current model of CS-MCT is setup and the reason of SSCB interruption failure is theoretically analyzed,and optimization of critical device structure parameter of CS-MCT and circuit parameter is carried out based on above analysis.According to the simulation and experiment results,it is found a contradictory relationship exists between on-state energy loss and fault current interruption capability of the SSCB based on CS-MCT,which implies a trade-off design of these two characteristics should be taken into consideration in a target application.