Research On Locomotive Conversion Systems Without Heavy Transformers

At present, speed increasing of electric locomotives is the key of our research. As lightweight of the electric locomotive is the premise of speed increasing, and weight of traditional huge power frequency transformer account for 1/3 of the electrical equipment,so,the traditional huge power frequency transformer is not suitable. In this paper, lightweight of the electric locomotive can be realized by the locomotive conversion system without the traditional huge power frequency transformer, then the electric locomotive can be further speeding up.In this paper, structure of the locomotive conversion system without the traditional huge power frequency transformer is analyzed, without the traditional huge power frequency transformer, the high voltage of power network is received by series of 4QCs, and the numbers of series modules are calculated by taking the data of CRH5 as example. Working principle of 4QC and the problem caused by series average-voltage is analyzed,working process of the full-bridge bidirectional DC/DC converter in phase-shifted control and other two methods is studied,and the bidirectional working processs,the problem caused by parallel current sharing is analyzed. The design methods of various parameters (inductance on ac side,parameters of secondary filter,energy storage capacitor) are given.The design of DC/DC converter is studied, the design methods of intermediate frequency transformer are given, also the parameters of DC/DC converter are designed.Controlled circuit of the system is studied.the control methods of input-voltage-sharing and output-current-sharing are analyzed in detail.Finally,some simulations are made.At first,the model of 4QC is built,the simulation waveform show that the voltage and current of input is in same phase,and the DC voltage is stable,and,the control model of input-voltage-sharing is built, the simulation results show that the input-voltage-sharing of series 4QCs can be realized;then, the model of DC/DC converter is built, the simulation waveform of phase-shifted control on DC/DC converter is proved to be the same with the theory waveform,and the control model of output-current-sharing is built, the simulation results show that the output-current-sharing of parallel DC/DC converters can be realized; also, the simulation results show that the input power factor of the line side is close to 1 and the output voltage is stable DC voltage,satisfying the performance of traction system.