Improved Direct Torque Control With Permanent Magnet Traction Motor For High Speed EMUs

In the past ten years,Chinese high-speed railway has developed from nonexistence to passing into existence,and now it has developed into the fastest-growing railway with the largest scale in the world.Today,highspeed EMUs still use a mature asynchronous AC drive system,in order to improve energy efficiency and reduce the loss of energy in the operation of EMUs,research on permanent magnet traction systems has become a hot topic in the study of major railway countries in the world.Compared with asynchronous traction motors,permanent magnet synchronous traction motors have a series of advantages such as light weight,small size,low noise and strong overload capability.The EMU is the main traction motor vector control,this control method has strong robustness,but requires decoupling operation in great quantities,and the control structure is complicated.The direct torque control can directly control the electromagnetic torque of the motor without a lot of decoupling calculation.In this paper,the control strategy of the interior permanent magnet traction motor is studied,the improved direct torque control is used to complete the following work.Firstly,the structure and control characteristics of permanent magnet traction system are analyzed,analyzing direct torque control strategy in depth,discussing the research status and improvement direction of direct torque control in detail,according to the mathematical model of the interior permanent magnet traction motor,the principle of direct torque control is analyzed,the simulation model of interior permanent magnet traction motor based on traditional direct torque control is establish in MATLAB2018/Simulink environment,and the simulation results are analyzed.Secondly,according to the lack of control performance of built-in permanent magnet traction motor based on traditional direct torque control,a control strategy of predictive space voltage vector interior permanent magnet synchronous traction motor based on maximum torque per ampare(MPTA)is proposed.The control strategy is theoretically deduced and a simulation model is established.The simulation results show that the proposed method has the advantages of stable inverter switching frequency,stable rotational speed and small torque ripple compared with traditional direct torque control.Finally,according to the control strategy mentioned above,for traditional flux observer based on voltage model used in the above control strategy has the problem of flux linkage observation error caused by integral initial value offset and integral saturation,the method of improving the flux linkage observation at home and abroad is analyzed in depth,a flux linkage online observer based on the extreme learning machine algorithm is proposed,the single hidden layer feedback neural network is applied to the closed-loop observation of the flux linkage,and the correctness of the algorithm is verified by simulation.