Study On Absorption Method Of Electric-brake Energy In Metro Traction System

The subway as the main means of transport in today’s large and medium cities,the using of traction power supply system is mainly AC/DC power supply mode,that is,from power supply of alternating current in traction substation is rectifying device rectifier into direct current,then to the catenary line for DC power supply,because electricity can only from traction substation to the subway traction power supply system,rather than the reverse flow,so when the subway at the time of braking is required,mechanical energy through the traction motor of metro trains the intermediate medium,achieved from mechanical energy to electrical energy conversion,this part of the converted to electricity back to the catenary line for DC,Some of the electric energy can be consumed by trains running on the same line,while the unconsumed electric energy will directly cause the voltage of the DC overhead line to rise.Grid over-voltage will trigger the protection of subway traction system.By studying the energy absorption mode of subway train on-board electric system,this thesis firstly analyzes the equivalent model of traction transmission system of urban rail vehicle and DC overhead contact network,establishes the equivalent model considering the actual grid voltage,actual lines and actual vehicles,and carries out simulation on this model.Under the condition of the current commonly used vehicle braking resistance,resistance to resistance and heat capacity are selected,and the simulation verify the over-voltage suppression effect of braking resistor,using FLOTHERM simulation software simulation of braking resistor temperature,the temperature of braking resistance is observed in real time,and established the braking resistance of thermal protection scheme.Considering the factors such as energy saving and emission reduction,the energy consumed by braking resistors will cause a certain waste.This thesis continues to study the characteristics of super-capacitors,analyzes the internal structure characteristics of super-capacitors,and equivalents the super-capacitors to a simple and feasible RC series model,and simulates the model.At the same time,according to the principle of super-capacitor charging and discharging,the bidirectional DC/DC converter is built,and the corresponding method of energy absorption and release is formulated,so that the energy can be effectively controlled.Finally,a comprehensive simulation model of the super-capacitor energy storage system is established.Through the simulation results,the control strategy adopted in this thesis is verified,and the purpose of the system can effectively absorb the electrical energy generated by the traction transmission system is realized.