Research On Main Circuit Scheme Of Cophase Continuous Traction Power Supply System

Existing single-phase traction power supply system frequency result in three-phase power system load unbalanced, reactive power and harmonic current pollution, and as a result of independent and random fluctuation of traction load, those problems are worse seriously. Electric phase break of traction network is the one of the weakest link to the high speed locomotive and heavy haul railway. Although some connection mode of cophase traction power supply system have been taken and these ways all cancel electric phase break, the effect is limited because power supply system not allow bilateral power supply on the division. As a key equipment of cophase continuous traction power supply system, power flow controller (PFC) came into being, and problems caused by electric phase break and other power quality can be solve.A brief description of cophase continuous traction power supply system is done in this paper. The structure of PFC which is the key of continuous power supply is analyzed, calculate parameters, and voltage outer ring current and inner ring controlling measures which is based on power conservasion principle are revealed. The AC/DC/AC topology comprehensive power flow controller used in cophase continuous traction power supply system is proposed. It is composed of two-level four-multiple PWM rectifiers and four cascaded multilevel inverters. It can achieve three-phase rectify in unit power factor and low harmonic content, transfer active power that traction load absorbs timely, supply controllability traction voltage which is used in traction load quickly, make traction supply system be characteristics of three-phase symmetrical pure resistive load, power quality interference between traction power supply system and power system is isolated. The basic electrical parameters of main circuit of AC/DC/AC topology comprehensive power flow controller were analyzed and calculated, a kind of power control method is proposed. Besides, the paper also analyze current of every traction substation in the condition of multiple traction substations to the power supply.MATLAB/Simulink simulations about AC/DC/AC topology comprehensive power flow controller have been done, and the results is included in the paper. The result has supported the system configuration, control strategy and parameter calculation method proposed in the paper, and the power factor, the power quality index of tri-phase unbalance factor and harmonics content are workable simultaneously.