Research On Control Method Of High-speed Train Traction Driver System

Traction drive control system of high speed EMU is one of the key technologies of modern high speed railway.Intensive study on the structure and control strategy of the existing traction drive system combined with modern control theory is the necessary way to develop the high performance,fully independent intellectual property rights of high speed EMU strategy,and it’s also the key way to promote globalization Strategy of China’s High Speed Railway.The AC drive system of the EMU is divided into the AC/DC part and the DC/AC part in this thesis,in which the control method of traction converter for AC/DC/AC traction drive system are studied and improved respectively.The control problem of a single phase three level pulse rectifier and the neutral point potential control algorithm of the three-level converter are involved in AC/DC part of EMU traction drive system.For the single phase three level pulse rectifier,firstly,the topology structure,mathematical model and the current and power control algorithms are analyzed.Secondly,the instantaneous power mathematical model of single-phase pulse rectifier and a model predictive direct power control(MPDPC)algorithm are discussed.Considering the problem of control delay in one-step predictive control,two-step model predictive algorithm is used based on one-step model predictive direct power control(OMPDPC),which is called two-step model predictive direct power control(TMPDPC)algorithm.The traditional DPC algorithm,OMPDPC algorithm and TMPDPC algorithm are simulated respectively,and the simulation results show the effectiveness of TMPDPC algorithm.Compared with DPC algorithm and OMPDPC algorithm,TMPDPC algorithm reduces the power fluctuation of the system,the control precision is higher,and the control system has good dynamic and static performance.For the difference of two converter DC side capacitor voltage in three level topology structure,the cause of the two capacitor voltage offset is analyzed;the influence of the fluctuation of the upper and lower amplitude on the neutral point potential is studied;and neutral point potential control method based on carrier amplitude shift is introduced in this thesis,which is used to balance the midpoint voltage by adjusting the upper and lower carrier amplitude.Compared with the traditional pulse conversion control method,the carrier amplitude shift control method does not need to change switch state frequently,doesn’t increase the switching frequency in system,and the algorithm is simple and easy to implement.The rotor flux oriented vector control algorithm is adopted for the control of three level inverter and traction motor in DC/AC part of traction drive system of EMU.The traction and braking characteristics and the design principle of the constant speed controller are analyzed.For the converter modulation strategy,the intrinsic relation and equivalence of space vector pulse width modulation(SVPWM)and sine pulse width modulation(SPWM)are analyzed in this thesis;the SPWM modulated wave equivalent with SVPWM modulation is obtained by calculation,achieving the same control effect with SVPWM through equivalent SPWM,which has a advantage of simple control structure,implementation simplicity and low cost.In the end,the simulations are carried out to validate the rationality and feasibility of rotor flux oriented vector control and equivalent SPWM algorithm.