Research On The Line Converter For Hybrid EMU

Hybrid EMU is a new type of EMU which consist of two kinds of power input, such as contact line or power battery(diesel generator). Line converter is the connector of power grid and traction inverter and the DCDC converter for power battery. The main circuit topology is single-phase PWM rectifier, which possesses the qualities of energy bidirectional flow, DC voltage stability and low AC current harmonic. When the train is pulling, line converter works in the rectifying mode, and supplys the DC voltage for motors. Moreover, it can save the regenerating energy to the grid when the motor works in braking state. In this dissertation, the main circuit topology and key control technology are discussed and studied, and a great deal of simulation and experiments verify the theoretical analysis and design.First of all, the line converter schemes of the other CRH trains are researched. The organization and power supply system of CRH1, CRH2, CHR3, CRH5are introduced, then the advantages and disadvantages of main circuit topology for each train’s line converter are compared. After that, combined with the special power supply mode of hybrid EMU, the main circuit topology of line converter is proposed, and the designed parameters of the system are confirmed.Secondly, design principle and convert formulas for main circuit parameters of proportionable prototype based on line converter are proposed. It is raised after analyzing the operating principle of PWM rectifier and the roles of each component in the circuit. Combined with the real parameters of hybrid EMU line converter, relevant calculating steps are given as an example. The simulation model of the real line converter and designed proportionable prototype are built in Matlab/Simulink, and the prototype experimental platform is built in the laboratory. The performances of both the simulation and experiment verify the equivalence of real system and designed proportionable prototype, which prove the effectiveness of the proposed design method.Thirdly, the control scheme for line converter is studied. The mathematical models for three-phase PWM rectifier in the stationary reference frame and rotating coordinate system are established first, then the control model for single-phase PWM rectifier in the rotating coordinate system is proposed, and the design methods of PI controller parameters are analyzed. After that, the conventional double closed loop control strategy based on the rotating coordinate system is analyzed. Furthermore, a new approach of generating imaginary system is promoted, which effectively improves the poor dynamics of the conventional approaches. Based on the control strategy, the design of PLL and carrier phase shifting are introduced. The simulation results verify the advantage of the improved control strategy in the dynamics.Lastly, an experimental system based on the hybrid EMU power supply system is built. The experimental items mainly include the basic function of line converter, carrier phase shift and temperature rising test. Also, debugging with traction inverter and DCDC converter are carried out briefly. The experimental waveforms and data demonstrate that the selected main circuit topology and control strategy in this dissertation are correct and feasible.