Modeling Of Through - Phase Traction Power Supply System And Fault Location Of Traction Network

At present, the most traction power supply system of electrified railway based on active filters and different connecting forms of transformer. In order to reduce the impact of traction power supply system on utility grid imbalance, the traction substation needs to be connected to the utility grid in turns, therefore an electric phase break section should be set at the output interface of a traction substation in the way of power supply. Because of the existing of the electric phase break, not only for three-phase power system to produce a large number of harmonics, reactive and negative sequence problems, but also severely restricted locomotive high-speed and heavy-duty running requirements. To solve these problems, based on power electronics technology and PWM technology of co-phase continuous power supply system is proposed. This system is a full transformation structure of the three-phase AC to single-phase AC, not only can solve the negative sequence, reactive power and harmonics problems, but also there is no need of the electric phase break. Therefore, the electric locomotive can be safety and steady accepted with power in anywhere of power range of traction substation.Firstly, this paper introducing the internal composition of the principle and achieve method of co-phase continuous power supply system. Analysis the control strategy of three-phase PWM rectifier and single-phase PWM inverter, through analysis and comparison of several control methods, and ultimately selected the double closed loop control strategy. Established the PSCAD simulation model of three-phase PWM rectifier and single-phase PWM inverter, thorough simulations were conducted to demonstrate the effectiveness of the proposed control strategies. Secondly, introduced the advantages and disadvantages of electric locomotive AC-DC-AC and AC-DC, and select the AC-DC-AC electric locomotive as the load of the co-phase continuous power supply system. While a more detailed analysis of the three-level PWM rectifier and control strategy. Through the analysis and compare of different control strategies, selected an improved balance control with a midpoint voltage of transient current control method was used in the rectifier. This part not only could provide reliable and stable power supply for the three-phase inverter, but also could maintain a high sinusoidal degree of input side current waveform. Detailed established the PSCAD model of single-phase three-level PWM rectifier, and the simulation results show the feasibility of this control strategy.Catenary is more prone to failure in electric railway system, but the high failure rate was earth short circuit in catenary, with PSCAD/EMTDC, transient responses of co-phase continuous power supply system at catenary earth short circuit are studied, including metallic earth short circuit and non metallic earth short circuit (high resistance ground).Traction substation and electric locomotives are connected to the catenary through a transformer. When the catenary failure, in the initial wave process, because a large winding inductance of transformer, current don’t mutation that was open state of transformers, fault current traveling wave propagation only in catenary. Through the wavelet transform modulus maxima by MATLAB tool of the fault current traveling waves at the output interface of each substation. By comparing the polarity of the fault current traveling wave modulus maxima the output interface of each substation, it can be realized the fault zone location of co-phase continuous traction power system, and thus obtain a criterion of fault interval mapping.