Research On Topology And Control Strategy Of Traction Drive System Of 24kV DC Locomotive

With the rapid development of power semiconductor technology and power electronics technology,the 24 k V flexible DC traction power supply system has been favored by many domestic and foreign due to its advantages of canceling electrical phase separation,good power quality(no negative sequence and harmonic problems),and long power supply distance.Tech workers are paying more and more attention.However,due to the relatively short time since the concept of this system was proposed,many studies on this system are still in the initial exploratory stage.In order to promote and improve the development of 24 k V flexible DC traction power supply system,this paper focuses on the research on the topology and control strategy of the locomotive electric traction drive system suitable for this system.The main research contents are as follows:(1)Combined with the requirements of electric locomotives for voltage,power,electrical isolation and bidirectional power flow in the 24 k V flexible DC traction power supply system,based on the topology of the electric traction drive system of the CRH5 locomotive,the traction transformer and four-quadrant converter were replaced with ISOP-DAB DCPET,a topology of locomotive electric traction drive system suitable for 24 k V DC power supply was proposed,and the design of the number of DAB sub-modules,rated transmission power,and circuit parameters in DCPET was completed.(2)The working principle,mathematical model and power transmission characteristics of the front-stage ISOP-DAB DCPET of the DC electric locomotive were studied.On this basis,in order to achieve the stability of the DC-side output voltage of the DCPET and the balance of the transmission power between the sub-modules,a control strategy based on single-phase shift control was adopted.Based on the MATLAB/Simulink simulation platform,the simulation model of DCPET was built,and the DCPET was tested under rated operation,load sudden change,power reverse transmission and other operating conditions,and the correctness and effectiveness of the DCPET topology,parameter design and control strategy were verified.(3)The working principle,mathematical model and control strategy of the traction inverter and motor at the rear stage of the DC electric locomotive were studied.Based on the MATLAB/Simulink simulation platform,a corresponding simulation model was built to test the traction motor under no-load start,sudden change of external load torque,and load start.At the same time,a co-simulation model including DCPET at the front stage of the locomotive and traction inverter and motor at the rear stage was built,and the locomotive was tested under three typical operating conditions(traction,constant speed,and regenerative braking),The feasibility and correctness of topology structure and control strategy of locomotive electric traction drive system with 24 k V DC power supply system were verified.(4)A hardware-in-the-Loop experimental platform with OPAL-RT OP5700 real-time emulator and digital controller(RTU-BOX 204)as the core was built.The structure and control strategy are verified by hardware-in-the-loop experiments.The experimental results further verify the feasibility and correctness of the proposed DC locomotive electric traction drive system topology and its control strategy.Finally,the work of this paper is summarized,and the deficiencies in this research are prospected.