Study On DC Circuit Breaker For Metro Based On Natural Commutation Technology

China is a major metro country whose stock and growth rate of metro projects are at the international advanced level,but the localization level of metro equipment is relatively low.DC circuit breakers play a key role in the protection of subway DC traction power supply systems.The products currently used rely on imports and cannot be turned off without arcs,which is prone to contact ablation and shorten the life of the circuit breaker.This paper analyzes the current mainstream technology route of DC circuit breaker,and the hybrid scheme combining the advantages of both mechanical and all-solid state is the hotspot of current research.The paper analysis and compares the forced commutation scheme and the natural commutation scheme.For the 1500 V voltage level of the subway traction power supply system,the hybrid scheme based on natural commutation is suitable for subway DC circuit breakers.The topology and working principle of natural commutation hybrid DC circuit breaker are introduced,and the influencing factors that affect the operating speed of the circuit breaker are studied,including the mechanical switching speed,arc voltage,solid-state switch conduction voltage drop and stray inductance.Make topological improve of DC circuit breaker of natural cummutation type.The equipment’s economy,quickness and reliability are comprehensively cinsidered,the design of hybird DC circuit breaker scheme based on natural commutation has been finished.The mechanical switch uses a high-speed vacuum switch based on electromagnetic repulsion,the solid-state switch uses an IGCT device,an RCD snubber circuit and a MOV pressure-limiting energy-absorbing device are applied.Compared with other power electronic devices,IGCT has the advantages of reduced on-voltage,large off capacity and strong anti-interference ability.It is suitable as a solid-state switch.A simulation model is build in Matlab / Simulink,in which the mechanical switch is replaced by the Mayr arc model,and the IGCT is implemented by the functional model.Through simulation verification,the experimental results show that: the hybrid DC circuit breaker based on natural commutation has a fast commutation speed,and can complete the breaking of the fault current within 2.7ms.