Research On Three-phase To Single-phase Traction Power Supply Mode Of Urban Railway Based On Balance Transformer

The electric locomotive load acts as a single-phase load,which brings serious harmonics,negative sequence and voltage fluctuations to the power system,which seriously affects the power quality and safe and stable operation of the power grid.As a kind of electrified railway,the municipal railway belongs to short-distance operation.The central city has a certain difficulty in the location of the railway resources and the location of the substation.Moreover,when the moving section is far away from the traction substation,the investment is large.Therefore,it is proposed to study the feasibility of using the mains 10 k V or 35 k V as the incoming power supply for the power train,including the engineering implementation of the 10 k V(35k V)boost traction substation,10(35)/ 27.5k V boost Transformer wiring,impact on the power quality of the power system,determine the critical short-circuit capacity of the access system.This paper first analyzes the research status of electric power quality control methods for electrified railways at home and abroad.Then,based on the balance transformer,based on the phase shifting capacitor,the three-phase to single-phase transformer power supply mode of scott balance transformer and the three-phase to single-phase power supply mode based on capacitive inductance phase shift are proposed.The working principle and applicable occasions are analyzed,and the critical short circuit capacity is also analyzed.and the research on three-phase to single-phase power supply is carried out based on phase shift method,and the working principle and applicable occasions are analyzed.Finally,the research on three-phase single-phase traction power supply scheme of YNvd transformer based on balance compensation is introduced.The correctness of the proposed scheme is verified by simulation of several typical operating conditions of locomotive.The specific paper mainly does the following aspects:Firstly,the characteristics of YNvd balance transformer are analyzed,and verified by simulation,Then based on the balance transformer,the three-phase to single-phase transformer power supply mode based on phase shift capacitor and the three-phase to single-phase power supply mode based on capacitive inductance phase shift are proposed.The structure and structure of the two methods are deduced in detail.The principle is verified by simulation experiments,and the advantages and disadvantages of the two methods are compared,and the critical short-circuit capacity of the corresponding mains power supply is given.Secondly,in order to solve the shortcomings of phase shifting method,a three-phase to single-phase traction power supply scheme based on balanced compensation YNvd transformer is proposed.The topology and working principle of the system are analyzed.The current detection method,current tracking control method and DC side capacitor voltage control method used in this paper are analyzed.Finally,the important parameters involved in the simulation system are explained.Combined with several typical operating conditions of the locomotive,the proposed YNvd transformer three-phase to single-phase traction power supply scheme based on balance compensation is simulated and analyzed.The scheme is verified from two aspects: negative sequence imbalance and harmonics.The simulation results verify the correctness of the proposed scheme and determine the critical short-circuit capacity of the power system through analysis.It provides a certain theoretical reference for the popularization of urban railways or short-distance power supply in the future.