Development Of Low-power Test Platform For AC-DC-AC Traction Substation

Because of its own structure and special characteristics of traction load,the existing electrified railway electric traction power supply system in China has the problems of three-phase unbalance,low energy feedback efficiency,injecting reactive power and harmonic current to the power system side.At the same time,due to the use of the phase sequence rotation power supply method,the adjacent power supply section is the nuetral section insulator,which reduces the safety and the carrying capacity of the electric locomotive.To solve these problems,the existing solution is to connect the power quality compensation device in parallel on the traction transformer,which is a passive compensation method and can not completely cancel the nuetral section insulator.Therefore,study the through-phase power supply has a great significance.In this thesis,a series-parallel multi-level converter structure are used as the basic topology of AC-DC-AC traction substation,a small-power test platform for AC-DC-AC traction substation has been designed and developed.Firstly,according to the characteristics of the AC-DC-AC power supply system and the functions required by the design requirements,from the characteristics of the input and output sides to the requirements of the power module,the overall topology of the main circuit of the test platform is gradually determined,ie,three-phase-single-phase back-to-backstructure,and the advantages of this topology are analyzed.The basic principle of single-phase PWM rectifier circuit is introduced,a double-closed-loop control strategy and a unipolar frequency-doubled carrier phase-shifted SPWM modulation technique are analyzed and adopted for the topology structure.Afterwards,the main circuit parameters of this design are designed,including the AC side inductance,DC side biquadratic filter and DC side support capacitor.The circuit model has been built in the MATLAB/Simulink environment.A Simulation of 15MVA capacity system is performed.And the feasibility of the program are verified by simulation results.Combining with the actual engineering environment,the low-power test platform for the AC-DC-AC traction substation has been designed,including the hardware structure of the low-power platform,the control system of the upper computer and the lower computer,and the CPLD program of the upper computer FPGA program and the lower computer.The oscilloscope is used to observe the debug results,indicating that the prototype has achieved basic functions.HS4 was used for the acquisition and harmonic analysis of the input and output data,verifying the effectiveness of the control system,and the reliability of the test platform,and the overall design.The rationality.It laid the foundation for the next step in the research and debugging of high power devices.The input and output data are acquired and harmonic are analysed,the effectiveness of thecontrol system,the reliability of the test platform,and the rationality of the overall design have verified.It laid the foundation for the next step in the research and debugging of high power devices.