Control Method Research Of MMC In The New Type Traction Power Supply System

Along with the development of high speed、heavy load railway traction system in our country, traditional traction power supply system cannot meet the requirements any more, a new type of traction power supply system based on the VSC-HVDC technology provides a opportunity to solve the problems. However, because there are some technical problems remains unresolved, the new type of traction power supply system is still on the stage of theoretical research. This paper in the view of the control techniques of MMC which was used in the new type of traction power supply system, the follow works has been done:1) The research background and significance of the new type of traction power supply system was introduced in this paper, the operation principle of several kinds of cophase traction power supply system technology and whose advantages and disadvantages were discussed to make clear the work of this paper.2) The system structure and the operation of the rectifier and inverter of the new type traction power supply system has been discussed systematically. The problem of voltage synchronous and current equilibrium problem in the parallel operation of inverters is analyzed.3) The control techniques of the MMC which is used in the new type traction power supply system was introduced systematically, include the modulation method, coordinate transformation problem and control method. A kind of double-loop control method to MMC which was used to supply power to passive network was analyzed and simulation verified.4) A kind of newly sliding mode variable structure controller design scheme to the three phase MMC in the new traction power supply system was proposed. The simulation result shows that the newly sliding mode variable structure controller has better control effect in such aspects as anti-interference, adaptability and dynamic compared to traditional double-loop control strategy.5) A kind of direct power control strategy without phase lock loop to the single phase MMC in new type traction power supply system was proposed for the phase synchronization caused by the single phase output and variable load in the traction system. It can avoid the effect caused by the phase lock failure or delay avoid the effect caused by the phase lock and make sure of the accuracy of the phase of the output voltage.6) Outline the research work and the significance of the study to the new type of cophase power supply system in this paper, and sums up some aspects needs to supplement and improve, which serve as a reference for future researchers.