The Research Of Urban Rail Transit Multi-pulse Rectifier Technology

During the past thirty years with the implementation of the reform and opening-up policy, China's economy has undertaken sustainable development, people's standard of living has been raised, and the urban construction has also been expanded. Many cities have started to plan and construct a rail transit project. Multi-pulse rectifier technology is the core of the traction power supply rectifier system which is also the most significant part of the urban mass rail transit system, the application of multi-pulse rectifier technology in the traction power supply rectifier system of the urban rail transit recently becomes the research focus for scholars at home and abroad.This paper has analyzed the ideal structure of the 24-pulse traction phase-shifting transformer using the space voltage vector control method and obtained the relationship between the turn number and the phase-shifted angle of the phase-shifting transformer by calculating the voltage vector of the phase-shifting transformer. It has also calculated the theoretical power quality using the Fourier transformation to demonstrate the superiority of the 24-pulse rectifier circuit indicators by the comparison between the results obtained from theoretical calculation and computer simulation.Concerning that the urban rail transit traction power supply system is a time-varying and AC-DC hybrid system containing AC and DC circuits and electric vehicles, the paper has established a load model for the power supply system based on different working conditions of metro vehicles in order to observe the power supply characteristics of each dynamic process in metro operation thoroughly. It has compared the working conditions of the load and traction power supply system supplied with ideal DC power supply and 24-pulse power supply under different working conditions. The power supply condition of the urban rail transit traction power supply system shifts from 24-pulse traction power supply to 12-pulse traction power supply caused by trouble-shooting has been analyzed and the balanced reactor has been added into the 12-pulse traction power supply rectifier circuit. The 12-pulse traction power supply rectifier circuit with balanced reactor comparing with common 12-pulse traction power supply rectifier circuit not only meets the requirement of various metro vehicle operations, but also greatly reduces the pollution of grid by harmonic wave and saves the energy costs.The 24-pulse traction rectifier unit has been designed based on urban rail transit DC1500V traction power supply system operations under different load rates. The operations under idle load,100% load and 300% load conditions as well as its influence on the side current of the traction transformer have all been analyzed. The results show that this system meets the demands of operations of the urban rail transit traction power supply under different load rates.