A novel direct torque control strategy of induction machine drives with simple duty ratio calculation

The traditional switching-based direct torque controlled (ST-DTC) induction motor drive is usually affected by large torque ripple and steady-state error of torque. The existing literature has proposed some methods to reduce torque ripple by optimizing the duty ratio of the active vector. However, these methods are usually complicated and depend heavily on motor parameters. Based on the analysis in instantaneous variation rates of stator flux and torque caused by each voltage vector, a simple and effective method considering the effect of machine velocity is proposed to acquire the duty ratio. The proposed scheme is able to reduce the torque ripple and steady-state error of torque significantly, while maintaining the simplicity and robustness of the traditional DTC at the most. Simulations and experimental results validate the proposed scheme. © 2015, The editorial office of Transaction of China Electrotechnical Society. All right reserved.