| In recent years,with the acceleration of urbanization process,people have shifted to cities in large quantities.As a result,large cities are crowded with people.In order to ease the current situation of urban congestion,large-scale rail transit systems are also being built in most of the cities in China.Therefore,the construction of domestic urban rail transit has reached its climax.At present,much braking energy in rail transit in many cities at home and abroad is consumed on the braking resistor,which results in the waste of braking energy,so the study of how to use braking energy is in line with the future development of urban rail transit and is also a practice of energy saving and environmental protection concepts which our country advocates.First of all,in the introduction section of Chapter 1 this article briefly describes the source of the problem,the principle of energy generation during train braking,and the research status of the use of regenerative braking energy at home and abroad,proposing the energy recycle method of combining inverted feedback and super-capacitor energy storage.In the second chapter,the braking energy recovery model of urban rail transit system is established and simulated with the data of Guangzhou Metro Line 5.From the simulation results,it can be known that the braking energy of urban rail transit vehicles is characterized by its high peak value and short time.In addition,The energy analysis model provides a basis for the recycling and utilization of regenerative braking energy.In order to solve the problem of great grid impact caused by the high power and short time of peak value,when the rail transit trains braking,in the third chapter of this thesis,a regenerative braking energy recovery method combining inverter feedback and energy storage is proposed,which is based on the analysis of the advantages and disadvantages of full power transmission back to the grid and full braking energy storage mode.In the process,the inverter feedback system absorbs most of the energy,which reduces the capacity,volume,and cost of the energy storage system;what's more,the energy storage system can reduce the impact that the regenerative braking energy has on the power grid,reducing the capacity of the inverter feedback system.Therefore,the capacity utilization of the inverter feedback system is increased.Considering the problem of how to distribute the regenerative braking energy between the two systems,this paper proposes three methods of capacity allocation,and makes simulation contrast on the three capacity allocation methods.It is concluded that under the strategy of comprehensive allocation,braking energy has the least impact on the DC power supply grid.Meanwhile when the capacity of the converters of the two systems is moderate this strategy has more advantages.At the end of this chapter,the implementation of two controllers is studied so as to facilitate the capacity design of energy storage system,and simulation is used to verify the control method and the rationality of the capacity design.To cooperate with the reverse feedback traction power supply system and reduce the impact that peak power has on the DC traction power supply system,the energy storage system composed of super-capacitors is studied in Chapter IV.Furthermore,the super capacitor-related problems are introduced,such as energy storage principle,characteristics,and equivalent model and the design method of the super-capacitor bank is proposed.Besides,the topology and control method of the bi-directional DC/DC converter are introduced.The method used to establish the mathematical model of the bi-directional DC/DC converter is state-space averaging method,which yields the transfer function,thereby setting the relevant parameters of the double closed loop control strategy of the super-capacitor energy storage system.Finally,a single-channel bi-directional half-bridge DC/DC converter is used as a simulation example to verify the feasibility of the control method. |
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