Design And Implementation Of Solid State DC Circuit Breaker Based On SiC MOSFET

DC circuit breaker plays an important role in the safe and reliable operation of DC distribution network.Compared with the mechanical type and mixed type DC circuit breaker,solid-state DC circuit breaker has advantages of simple structure,fast switching speed,arc free operation and reliable performance.And Compared with the solid-state circuit breaker based on Si devices available,the solid state DC circuit breaker with wide band gap device SiC MOSFET as the switching element has advantages of high withstand voltage level and low conduction loss,which is becoming the development trend of DC circuit breaker.However,the solid state DC circuit breaker based on SiC MOSFET is faced with problems of no accurate simulation model,needing to design adaptive drive and inhibiting overvoltage when the device is turned off.In order to give full play to the superior performance of SiC power devices,in this paper,the equivalent circuit level model of SiC MOSFET is established,the key problems of the application of SiC MOSFET in circuit breaker are analyzed,such as switching characteristics of SiC MOSFET,and a solid state DC circuit breaker is designed and tested.The research work in this paper mainly includes:(1)The modeling method of SiC MOSFET is studied,and the equivalent circuit model of SiC MOSFET is established.First,this paper analyzed the structural features of SiC MOSFET,and determined the key parameters of the equivalent model by means of referencing the datasheet of SiC MOSFET.Secondly,the nonlinear characteristics of parasitic capacitance of SiC MOSFET and the effect of driving negative pressure and parasitic inductance on the device characteristics are considered,and the equivalent circuit model of 1.2kV SiC MOSFET is established.Finally,the static characteristics and dynamic characteristics of the equivalent circuit model are simulated and the results are compared with the experimental results.All of these provide basis for the design of adaptive drive and prototype of solid state DC circuit breaker based on SiC MOSFET.(2)The switching performance and its influencing factors of solid state DC circuit breaker based on SiC MOSFET are studied.First of all,the switching process of SiC MOSFET is analyzed,and the influence of the internal parameters of the device on the switching characteristics is analyzed.Secondly,the influence of the external parameters such as the driving resistance,the driving capacitor and the driving voltage on the switching characteristics of SiC MOSFET is studied,and the performance requirements of SiC MOSFET for the drive circuit are summarized.Finally,the mechanism of the voltage spike which is produced at the initial period of turn-off time of the solid state DC circuit breaker based on the SiC MOSFET is studied,and the method of improving the traditional parallel RC circuit to suppress the voltage spike is proposed.All these research results provide a theoretical basis for the design of SiC MOSFET adaptive drive and the prototype of solid state DC circuit breakers.(3)Based on the characteristics and performance of SiC MOSFET,a solid state DC circuit breaker prototype based on SiC MOSFET is designed.First of all,according to the requirements of the driving circuit for solid state DC circuit breaker based on SiC MOSFET,the adaptive drive of SiC MOSFET is designed.Secondly,according to the performance requirements of solid state DC circuit breakers,the main circuit,control circuit,current detection circuit and snubber circuit are designed.Furthermore,the PSPice software is used to simulate the design of the solid state DC circuit breaker and the function of each part of the DC circuit breaker is tested.Finally,a prototype of DC circuit breaker based on SiC MOSFET is made,and the performance of the prototype is tested and analyzed.