Research On SiC JFET DC Circuit Breaker And Its Series And Parallel Technology

With the increasing application of distributed energy systems and DC loads,DC power distribution systems are receiving more and more attention as a more efficient means of distributed energy and DC load access.And the lack of reliable DC protection devices is one of the most critical challenges to further development of power distribution systems.The unique fast action performance of the solid-state circuit breaker makes it more suitable for DC power distribution protection.The wide-bandgap semiconductor device represented by silicon carbide(SiC)will promote the new generation of wide-bandgap solid-state circuit breaker by its high working voltage and low on-state loss.Currently,limited by the capacity of SiC power devices,the wide-bandgap DC solid-state circuit breakers cannot be used in high-voltage and high-current applications.Studying the series-parallel technology of SiC power devices is an effective way to expand the capacity of wide-bandgap DC solid-state circuit breakers.Firstly,an ultra-fast,programmable solid-state DC circuit breaker with a normally-on SiC JFET device as the main switch is designed.In the normal operation of the DC system,the advantages of the on-state SiC JFET with low on-state loss are fully utilized.In the case of short-circuit or over-current faults,the JFET drain source voltage is used as the sampling signal,and the control circuit determines the fault type according to the sampling signal,then sends a corresponding driving signal to the driving circuit to turns off the SiC JFET,and the fault is cut off.The topology structure of the solid-state circuit breaker and the fast programmable drive circuit are designed.The concept and theoretical working process of each part of the circuit breaker are analyzed in detail.Secondly,the series-parallel technology of SiC JFET devices is studied.The turn-on and turn-off process of SiC JFET devices is analyzed.The effects of the device itself and the parasitic parameters of the circuit on the turn-on and turn-off process are analyzed.The parameters affecting the parallel current sharing of the devices are summarized,and the main influence parameters are simulation analysis in parallel connected circuit.Based on above analysis,the device parallel dynamic and static current sharing measures are proposed,and the 8-tube parallel circuit for DC solid-state circuit breaker is designed.The series influencing factors of power devicesand voltage sharing measures proposed before are introduced.The single-drive cascade topology and its application are introduced in detail,and the single-drive series circuit topology for DC solid-state circuit breakers is designed.Finally,the short-circuit fault test platform was built.400V/38 A solid-state DC circuit breaker,400V/300 A solid-state DC circuit breaker and 1500V/38 A solid-state DC circuit breaker prototype were developed.The quick-acting and programmability of the 400V/38 A solid-state circuit breaker are verified.Dynamic and static current sharing characteristics of 400V/300 A solid-state DC circuit breaker parallel devices and dynamic and static voltage equalization characteristics of 1500V/38 A solid-state DC circuit breaker series devices are also verified.