DC Traction Power Supply System Based On Thysistor Rectifier

With gradually accelerated process of urbanization, urban rail transit becomes the best choice for easing problems in urban public transit. The safety and reliability of DC traction power supply system is based on safe and smooth operation of urban rail transit. According to existing problems in technical and economic aspects of DC circuit breaker in DC side of DC traction power supply system, a new type of DC traction power supply system is studied based on thyristor rectifier unit, which can save the number of DC circuit breaker, and its protection methods. Considering the problem of big pulsation and obvious characteristic frequency harmonics of the output voltage in DC side of 24-pulse thyristor rectifier unit, a new program of improving the quality of power supply in traction side is put forward. The program is that thyristor rectifier unit supplies for BUCK-BOOST converter and converter output is used as supply voltage in traction side.In order to save the number of DC circuit breaker or reduce its burden, a new type of DC traction power supply system is further researched based on thyristor rectifier unit. After introducing the structure of DC traction power supply system based on thyristor rectifier unit, detailed analysis for selection of thyristor rectifier unit and the time that the new system uses in shutting off short-circuit fault are carried out; moreover, the control of thyristor rectifier unit and methods and processes of removing all types of DC-side short-circuit fault are studied, which is used as both thyristor rectifier and DC-side isolation switch. Considering the problems in the scope of power off and the workload of the DC circuit breaker when removing the fault, the program of reserving DC circuit breaker and partition are put forward according to steady-state current value of feeder when it breaks down. And the simulation model is built on the simulation platform of Matlab/Simulink to verify its feasibility. In addition, the pros and cons of each system are compared in the scope of power off, the workload of the DC circuit breaker, economy and time of shutting down the fault, which can provide the reference for the choice of the programs of DC traction power supply system in the spot.To solve the problems of big pulsation and obvious characteristic frequency harmonics of the output voltage in DC side of 24-pulse thyristor rectifier unit, a new plan of improving the quality of supply in traction side is proposed. The plan is that thyristor rectifier unit supplies for BUCK-BOOST converter and converter output is used as supply voltage in traction side. Following the introduction of structure of the new plan, working principles, preferences and control methods of converter are presented. An improved multi-loop control strategy is put forward to further improve response speed of system. Then the catenary voltage magnitude is analyzed to release the maximum distance between two traction substations. And the simulation model is built on the simulation platform of Matlab/Simulink. In the end, simulation result shows that improved multi-loop control strategy improves the response speed of system; The new plan can improve the quality of supply in traction side and increase the distance between two traction substations; And it can shut down the DC-side short circuit fault by thyristor rectifier.