International Conference on Emerging Technology Trends on Advanced Engineering Research (ICETT’12) Proceedings published by International Journal of Computer Applications® (IJCA) 34 A Novel MATLAB/Simulink Model of PMSM Drive using Direct Torque Control with SVM K Narasimhaiah Achari Associate Professor Dept. of EEE GPCET, Kurnool Kurnool (Dist), A.P., India B Gururaj Assistant Professor Dept. of EE SJCET, Yemmiganur Kurnool (Dist), A.P., India D V Ashok Kumar Professor & Principal Dept. of EEE SDIT, Nandyal Kurnool (Dist), A.P., India M Vijaya Kumar Professor Dept. of EEE JNTUA University, Anantapur, A.P., India ABSTRACT A modified Direct Torque Control (DTC) by using Space Vector Modulation (DTC-SVM) for permanent magnet synchronous machine (PMSM) drive is proposed in this paper. DTC-SVM technique improves the basic DTC performances, which features low torque and flux ripple and also fixed switching frequency. The computer simulation results, in Matlab/Simulink, demonstrate the effectiveness of the proposed control scheme which improves the performance of the PMSM. Keywords PMSM, DTC, DTC-SVM, Torque ripple, Flux ripple, Fixed switching frequency. 1. INTRODUCTION Direct Torque Control (DTC) method has been first proposed and applied for induction machines in the mid- 1980’s as reported in [1]. This concept can also be applied to synchronous drives [2]. Indeed, in the late 1990s, DTC techniques for the interior permanent magnet synchronous machine appeared, as reported in [1].Permanent magnet (PM) synchronous motors are widely used in high-performance drives such as industrial robots and machine tools to their advantages as: high efficiency, high power density, high torque/inertia ratio, and free maintenance. In recent years, the magnetic and thermal capabilities of the PM have been considerably increased by employing the high coercive PM material [2]. For some applications, the DTC becomes unusable, despite it significantly improves the dynamic performance of the drive compared to the vector control due to torque and flux ripples. Indeed, hysteresis controllers used in the conventional structure of the DTC generates a variable switching frequency, causing electromagnetic torque oscillations [4], this frequency is also varying with speed, load torque and hysteresis bands selected [1]. In addition, a high sampling frequency needed for digital implementation of hysteresis comparators and a current and torque distortion caused by sectors changes [2]. Several contributions have been proposed to overcome these problems, by using a multilevel inverter: more voltage space vectors available to control the flux and torque. However, more power switches are needed to achieve a lower ripple and almost fixed switching frequency, which increases the system cost and complexity [2]-[5]. In [1] and [2], two structures of modified DTC have been proposed to improve classical DTC performances by replacing the hysteresis controllers and the commutation table by a PI regulator, predictive controller and Space Vector Modulation (SVM). In this paper, a modified DTC algorithm with fixed switching frequency for PMSM is proposed to reduce the flux and torque ripples. It is an extension of the modified DTC scheme for the PMSM proposed by the authors in [1] and [2]. The performance of the basic DTC and the proposed DTC scheme is analyzed by modeling and simulation using MATLAB. 2. DTC AND DTC-SVM STRUCTURES Figures 1 and 2 represents two system configuration of DTC controlled PMSM drive respectively; both of them use the same flux vector and torque estimators. However, torque and flux hysteresis controllers and the switching table are replaced by a PI torque controller and a predictive calculator of vector voltage reference to be applied to stator coils of the PMSM. Fig.1. Basic DTC scheme for PMSM drive with speed loop In the proposed scheme of DTC-SVM with speed loop control, shown in Figure.2, after correction of the mechanical speed through a PI controller, the torque PI controller delivers V sq voltage to the predictive controller and also receives, more the reference amplitude of stator flux Ө sr , information from the torque and flux estimator namely, the amplitude and position ϴ s of the actual stator flux and measured current vector.