Research On Key Technology Of Phase Selection And Closing Of High-speed EMU Vehicle-mounted Circuit Breaker

With the rapid development of high-speed railways,the manufacturing level of EMU equipment in China continues to improve.Vehicle-mounted circuit breakers are the key components connecting the traction network and EMUs.Their performance directly affects the safe operation of EMUs.When the EMU passes over the phase splitting,the circuit breaker operates through opening and closing to ensure that the EMU passes the neutral zone smoothly and realizes the commutation process.At present,the closing of EMU circuit breakers in China belongs to random closing.When the circuit breaker is closed,the energy continuously changes between inductive and capacitive components,causing circuit oscillation to produce overvoltage.The occurrence of closing overvoltage will not only impact the catenary,but also destroy the stability of the EMU system.This paper investigates the problem of closing overvoltage suppression and investigates the current status of closing overvoltage suppression and phase control technology research,and aims to use phased closing technology to reduce closing overvoltage.Firstly,the mechanism of closing overvoltage is analyzed,and the transient process of EMU over-phase separation is researched.The closing process when EMU leaves the electric phase separation is deeply analyzed,and its equivalent circuit model is established.The relationship between closing overvoltage and closing angle is obtained.The actual closing overvoltage is tested to verify the correctness of the theoretical analysis.Then,it conducts simulation research on the closing overvoltage.The mathematical models of the EMU,traction network,traction substation,and AT in the traction power supply system are analyzed separately,and the overall traction power supply system simulation model is built.The inevitability of closing overvoltage is verified by simulation.Then based on the simulation model,the actual operation of the electrified railway is simulated and analyzed,which is divided into single-EMU load operation and multi-EMU load operation.For single vehicle load,consider the effect of closing time on closing overvoltage.For multi-vehicle loads,considering the two aspects of the main line and the adjacent line respectively,the effects of the EMU load impedance angle,EMU speed and load distance on the closing overvoltage are analyzed.Finally,according to the simulation,the circuit breaker selection is analyzed,and it is found that the bistable permanent magnet mechanism vacuum circuit breaker meets the requirements of phase-controlled closing.And based on the permanent magnet circuit breaker as the prototype,carry out the circuit breaker pre-breakdown test,study the phasecontrolled closing process,and formulate the phase-controlled closing plan.Finally,the phase-controlled closing scheme is tested and verified,and the results show that the closing overvoltage can be effectively reduced when the closing angle is between(-8o,15o).