| In order to meet the low-carbon operation and sustainable development of country’s electrified railways,as well as the safe and stable operation of country’s Sichuan-Tibet Railway,connecting the photovoltaic-storage system to the traction power supply system can not only improve the power supply penetration rate of new energy and renewable energy,fundamentally innovate the energy supply mode of electrified railway,and at the same time,it can further reduce energy consumption and achieve energy saving and emission reduction.However,the access of the photovoltaic-storage system makes the entire vehicle network system become a more complex single-phase power electronic system.There may be interactions between different single-phase power electronic devices in the EMUs and the photovoltaic-storage system,which may cause new oscillation question.Therefore,it is of great theoretical and practical significance to study the electrical stability of the photovoltaicstorage system connected to the traction power supply system.This paper focuses on the lowfrequency oscillation problem of vehicle-photovoltaic-storage-network and the oscillation suppression measures.The main research contents include:(1)A state space model of the CRH5 EMU is established;Based on this model,the lowfrequency oscillation mode of the CRH5 EMU system is studied when the single train is connected to the grid and the multi-vehicle is connected to the grid by using the eigenvalue analysis method.The influence of operating parameters and control parameters on different low-frequency oscillation modes is analyzed.The simulation model is built in Matlab/Simulink,and the correctness of the theoretical analysis results is verified by simulation.(2)The state space model of the photovoltaic-storage system and vehicle-photovoltaicstorage-grid system are established in detail;On this basis,the dominant low frequency oscillation mode of the vehicle-photovoltaic-storage-grid system is studied by using the eigenvalue analysis method;Compared and analyzed the change of the dominant lowfrequency oscillation mode of the system before and after the integration of the photovoltaicstorage system into the traction power supply system;The influence of vehicle-side control parameters,vehicle-side electrical parameters,grid-side electrical parameters,photovoltaicstorage system control parameters,and photovoltaic-storage system electrical parameters on the low-frequency oscillation mode of the system is analyzed in detail.;The participation degree of the different control links in the photovoltaic-storage system and the EMUs on the oscillation mode and the dynamic interaction characteristics are analyzed by calculating the participation factor.The simulation model is built in Matlab/Simulink,and the correctness of the theoretical analysis results is verified by simulation.(3)Based on the control strategy of CRH5 EMU,a feedforward control strategy with the input signal of the current disturbance at the parallel node of the EMU rectifier or the voltage disturbance at the DC side is proposed to suppress the low-frequency oscillation of the vehiclephotovoltaic-storage-grid system.The eigenvalue analysis method is used to analyze the influence of the feedforward coefficient on the stability of the dominant low frequency oscillation mode in the two feedforward controls,and the range of the feedforward coefficient is determined.The simulation model is built in Matlab/Simulink,and the effectiveness of the proposed suppression strategy is verified by simulation. |
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