| Energy is the core substance basis of a country,which determines the lifeblood of social and economic development.With the rapid development of China’s rail transit industry,the demand for energy is also increasing.Energy saving and recycling has become a hot research topic.Train regenerative braking is widely used in multiple units,electric locomotives,metro trains and other fields because of its energy recycling,but there are also problems such as imperfect technology and low energy utilization rate.Therefore,it is necessary to study on improving the energy utilization rate of metro train regenerative braking,so as to help the green energy-saving development of rail transit industry.Firstly,this paper studied and summarized the development and application status of regenerative energy utilization at home and abroad,analyzes the mechanism of regenerative braking and completes the calculation of braking energy.A scheme of super capacitor storage and discharge system for subway train based on DSP control is proposed,which is divided into two parts : main circuit and control circuit.The main circuit is mainly composed of power transmitter and super capacitor module.The power transmitter adopts bi-directional full bridge DC/DC converter with isolation,which meets the technical requirements of bi-directional transmission of system energy.Accorded to the system design requirements,the parameter calculation of main circuit components is completed.At the same time,based on the simple model of super capacitor,the charging and discharging characteristics and series parallel characteristics are analyzed.On this basis,combined with the single braking energy of metro train,the selection of super capacitor unit and the design of module are completed,which lays a theoretical foundation for the design of system control strategy.The control circuit takes DSP as the control core,and completed the design of drive circuit,protection circuit,isolation circuit and hardware selection.Based on the analysis of the principle of single phase shift control and its switching mode,the mathematical model of bidirectional DC/DC converter is established,and the control strategy of phase shift double closed loop is proposed.The bus current sampling signal gets the feedback signal through the sensor,carries on the AD conversion to the feedback signal,sends the converted result to the DSP to compare with the given value,so as to determine the working mode of the storage and discharge system;then carries on the AD conversion through the input/output voltage and current sampling signal,and carries on the PID operation with the given value in the DSP to obtain the corresponding phase-shift angle,through the phase-shift control The adjustment of phase angle realizes the change of energy size and direction.According to the control strategy,the whole system model is built in Matlab/Simulink simulation software,and the simulation experiment of super capacitor charging and discharging is completed.The simulation waveforms of DC bus voltage without storage and discharging system and bus voltage with storage and discharging system are compared,which proves the rationality of the system design.The software design of the main program and subroutine of the system is completed,including PWM signal output,PID control and AD sampling subroutine.The corresponding program flow chart and part of the program code are given.Finally,the prototype of the super capacitor storage and discharge system of metro train is built and the related experiments are carried out.The test results showed that the super capacitor storage and discharge system designed in this thesis can basically meet the expected technical requirements,and can realize the recovery and reuse of regenerative braking energy. |
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