Control Of Electric Locomotive Traction Converter

The railway line of our country is the world’s busiest, Its total operation mileage andthe passenger account for about the global6%and24%respectively. Along with thedevelopment of the economy, and the more advantages of the High speed railway which arehigh-efficiency, large volume, low cost of energy, covering Less Space, punctuality, andgood economic returns, the transportation equipment manufacturing industry has being oneof the critical support of the strategic industries. The technologies breakthroughs andinnovations of the electric traction are playing a crucial role in rapidly improving thetechnology level of the equipment transportation.Compared with France, Japan and Germany, the domestic research and developmentstill has the gap, we need to keep up with the development of international technology.This paper is based on “LanJian” electrical locomotive which owns the high powertraction converters transmission system. The article mainly focuses on the4-quadrantconverter control strategies, modulation technologies of motor inverter and the circuitgrounding protection design.Based on introducing the main circuit of the traction converter and the characteristic ofthe converter which is high-voltage, high-power, low-switching frequency, adopted indirectcurrent control strategy and decoupling control the active and reactive current whichimprove the control precision and performance fast. As the two converters paralleloperation，designed the carrier phase shifting control to improve converter’s switchfrequency and current-sharing strategy to maintain system balance.And then established the Matlab/simulink model of the traction system.A set ofswitching methods of PWM strategies is presented, including firstly from asynchronousPWM to synchronous PWM, secondly synchronous PWM to SHEPWM, and finallyswitching between different carrier ratios among SHEPWM. By analyzing and comparingthe simulated waveforms of switching different modulation modes, the right points ofswitching are determined, assured the smooth transitions.These switching methods areconfirmed by the experiments on the traction system and the current transients areeffectively avoided.At last, in order to explain the phenomenon which was appeared on the groundingprotection circuit when measuring the grounding voltage. The electromagnetic interferenceof the circuit was analyzed. The common-mode interference can not be ignored.The methodof extracting signals, filtering common-mode voltage is given. The method is confirmed bythe experiments on the traction system and the common-mode voltage interference iseffectively removed.The paper’s control strategies and design have been verified by traction experiments.