Study On Control Of Parallel Connected Traction Motors In EMU

Because of the advantages of low cost,lightweight and compact structure,multiple asynchronous traction motors are driven by a single inverter in parallel used in EMU.However,the difference of motor parameters,wheel diameter and wheel-rail adhesion will affect the train control performance.Therefore,it is necessary to study the parallel operation control of asynchronous traction motor for EMU.In this paper,the parallel asynchronous traction motor under the same bogie of EMU is taken as the control object,and the vector control method of parallel motor and the adhesion control method of train are studied.Firstly,the vector control principle of asynchronous traction motor is introduced,and the effects of parameter difference,wheel diameter difference and abnormal adhesion on the torque imbalance of parallel motor are analyzed.Secondly,the basic theory of wheel-rail adhesion is introduced.Based on the adhesion theory and the dynamic model of transmission system,the equivalent load model of parallel asynchronous traction motor under the same bogie is established.Subsequently,the control method of average rotor flux orientation based on indirect vector control of induction motor is studied.Neglect the parameter difference with less influence for the time being.The load model established in the previous section is applied to simulate the wheel diameter difference,which proves that the control method can make the parallel motor output higher average torque.Considering that the parallel motor controlled by this method is difficult to start stably when the wheel diameter difference is large,the weighted rotor field orientation control method is adopted.The control weight of the parallel motor can be allocated effectively by setting the weight coefficient reasonably,which solves the starting problem when the wheel diameter difference is large.The excitation compensation is introduced into the control system to effectively reduce the torque difference between the motors.Finally,aiming at the situation that EMU inevitably runs on bad adhesion rail surface,the adhesion control algorithm of train is studied.In order to overcome the shortcomings of the traditional correction method,the optimal adhesion control algorithm is adopted.For the reference of adhesion control,a full-dimensional state observer,steepest gradient method and weighted rotor field orientation method are used to achieve optimal adhesion control.The simulation results shows that the optimal adhesion control method can improve the utilization ratio of wheel-rail adhesion under the premise of restraining idle wheelset.