Research On Hybrid DC Circuit Breaker For Urban Rail Transit Based On Coupling Reactor

The DC circuit breaker is an important equipment for the control and protection of urban rail transit system.Its on-off reliability directly affects the operation safety of DC traction power supply system.At present,the DC circuit breakers used in DC traction system in China are mainly air-type DC circuit breakers produced by foreign companies,which have some problems such as long breaking time and serious ablative of arc extinguishing grid.The existing medium voltage hybrid DC circuit breaker mainly adopts natural commutation,which has some problems such as difficult commutation and slow speed in the process of high current breaking.It is of great significance to study the topology structure and regulation method of fast commutation for high speed breaking of hybrid DC circuit breaker.In this paper,a hybrid DC circuit breaker topology based on coupling reactor is firstly proposed.By analyzing its working principle and process,the topology can effectively accelerate the current commutation process and realize non-arc or less arc breaking of vacuum switch.Secondly,the simulation model of hybrid DC circuit breaker based on coupling reactor was established.The influence of different coupling reactor parameters on the current commutation process was calculated and compared to obtain the current commutation characteristics under the condition of different coupling coefficients and the ratio of inductance of primary and secondary winding.Then,according to the relationship between the current commutation time and the natural opening time of vacuum switch,the critical curve of vacuum switch without arc breaking is obtained,and then the parameter range of coupling reactor is determined.Finally,the parameters of the coupling reactor used in the topology structure are preliminarily determined based on the engineering practice.When the inductance of the primary and secondary windings of the coupling reactor is 150 μH and 20 μH respectively,and the coupling coefficient is 0.98,the arc breaking of the vacuum switch can be realized.Compared with the uncoupled reactor,the current commutation time is shortened from 1.4ms to 0.5ms,and the current peak value is reduced from 15.3kA to 11.8kA,which can further realize the turn-off at a lower current,thus reducing the number of IGBTs in parallel,saving economic costs,and protecting equipment safety.According to the above simulation parameters,the key parts of the structure design and device selection,the machine structure adopts a three-layer layout scheme,to achieve a compact design.On the basis of the above research,the hybrid DC circuit breaker experimental platform based on coupling reactor was built,and the fault current breaking test was carried out on the 1.8kV/10kA DC experimental platform.The experimental results show that compared with the traditional hybrid DC circuit breaker,the current communication time of this structure is shortened from 283 μs to 204 μs,and the peak value of fault current is reduced by 47%.The error range between the simulation results and the experimental results is within ±5%.The experimental results preliminarily verify the validity and feasibility of the hybrid DC circuit breaker based on coupling reactor,which provides a certain reference for the development of engineering prototype.