Direct torque control combined with extended state observer for traction motor applied in north-south high-speed railway train

Abstract

High-speed trains are becoming increasingly popular in developing countries thanks to their ability to protect the environment and save fossil energy resources that are gradually depleting. Induction motors (IMs) are considered the first choice for traction systems for high-speed trains thanks to their high efficiency and torque-to-current ratio. To optimise the speed control performance of IMs under disturbances, the proposed direct torque control (DTC) algorithm enables direct control of motor torque and magnetic flux without a current loop. The DTC method has been proven to be an effective solution thanks to its fast response and precise control of torque and magnetic flux without the need for complex current control loops or magnetic field orientation. However, the traditional DTC method still has limitations, such as large torque ripple, current fluctuations, and difficulty controlling under rapidly changing load conditions. These limitations can cause noise and vibration and reduce the system's service life, especially in applications requiring high accuracy, such as high-speed rail trains. In addition, a load torque observer based on the Extended State Observer (ESO) is proposed to estimate the accuracy of the train's traction force under model deviation, thereby improving the operability and reliability of high-speed trains. The results show that combining the DTC and ESO provides a sound, stable motor drive system. In theory, the research results have been verified by simulation in MATLAB/Simulink using data collected from the North-South High-Speed Railway Train project in Vietnam.