Research On Rectifier Of The Diesel/electric Hybrid Multiple Units

In recent years,with the rapid development of rail transportation industry,hybrid trains has become a hot research spot.Some of China's railway lines are still in the state without the establishment of power grids.The diesel/electric hybrid multiple units break the traditional model of DMU and EMU,and also realize the integration of electrified and non-electrified sections.Among them,"electric" refers to the traction power grid,"diesel" refers to the diesel generator.The vehicle is powered by the high voltage power grid in the electrified section,and which is powered by diesel generator in non-electrified section.This paper studies the rectification system of the diesel/electric hybrid multiple units.On the basis of theoretical research,the topology structure of hybrid system is designed.With the main circuit parameters determined,modeling and simulation are finished in MATLAB/Simulink,and then the simulation results are analyzed.According to the results of harmonic analysis,the original controller of the rectifier system is improved with the application of PFC circuit for the diesel and power side,and the design of ADRC link for the non-linear PWM rectifier.The main works are as follows:First,according to the operation characteristics of the hybrid system,three kinds of topology structures are designed,including the common inverter link,the common rectification link and the common intermediate DC link.By comparing and analyzing the advantages and disadvantages of the above three forms,the topology of the common intermediate DC link is selected.Then,after selecting the topology structure of the hybrid system,the rectification system is modeled and simulated on the platform of the hybrid train.The main circuit parameters are selected for the power side and the diesel side of the rectifier system.The simulation results show that the DC output voltage on the power and diesel side is stabilized within Is,and the fluctuation range is small to reach the desired rectification target.The power and diesel side are analyzed with harmonic theory,the harmonic voltage of the diesel mode is much smaller than which of the electric mode.Therefore,the quality of the diesel generator is better than that of the power grid,and both of them could share the intermediate DC link.In the electric mode,twofold shift carrier phase technology is achieved on the single-phase PWM rectifier,which makes the harmonic voltage content reduced.What's more,the rectification link has been improved,and the power factor correction(PFC)control is carried out on the power and diesel side respectively.First,a single-cycle controller of PFC circuit is designed,and then simulation model is established in simulink.The simulation results show that the PFC technique can effectively reduce the current harmonic content on the AC side and make the power factor closer to 1.Last,a non-linear control strategy-auto disturbance rejection control(ADRC)technique is applied to the hybrid rectifier system for the non-linearity of the pulse rectifier.Firstly,the controller is designed,and then the S function is used to simulate in the simulink environment.The influence of the ADRC control strategy and the traditional control strategy on the rectifier system is compared.The simulation results show that compared with the traditional PID control method,the DC link voltage overshoot is relatively smaller,the time required to reach the stable voltage is shorter,the voltage fluctuation range is smaller,the total harmonic voltage content is lower,and the power factor is closer to 1 in the ADRC control method to achieve the desired results.And the artificial disturbance signals are added to the original simulation system.The capacity of resisting disturbance of the rectifier system with the ADRC control strategy is better than the PID control strategy,so which has better robustness.