Abstract—This paper presents a speed sensorless direct torque control scheme using space vector modulation (DTC-SVM) for permanent magnet synchronous motor (PMSM) drive based a Model Reference Adaptive System (MRAS) algorithm and stator resistance estimator. The MRAS is utilized to estimate speed and stator resistance and compensate the effects of parameter variation on stator resistance, which makes flux and torque estimation more accurate and insensitive to parameter variation. In other hand the use of SVM method reduces the torque ripple while achieving a good dynamic response. Simulation results are presented and show the effectiveness of the proposed method. Keywords—MRAS, PMSM, SVM, DTC, Speed and Resistance estimation, Sensorless drive I. INTRODUCTION C motor control has attracted much attention recently in the power electronics field [1]. Permanent magnet synchronous motors (PMSM) have been widely used as servo- machines over the last two decades. In recent years, they are used more in the variable speed applications due to some advantages like: more simplicity, low dependency on the motor parameters, good dynamic torque response, high rate torque/inertia [2] Since the advent of the direct torque control (DTC) for induction machines in the 1980's as proposed by M. Depenbrock [1] and Takahashi [3], its research has been becoming ever more prevalent in the society. The main advantages of DTC are the simple control scheme, a very good torque dynamic response, as well as the fact that it does not need the rotor speed or position to realize the torque and flux control, moreover DTC is not sensitive to parameters variations (except stator resistor) [1]-[5]. However, it still has some disadvantages that can be summarized in the following points: • Difficulty variable switching frequency, • High current and torque ripple; • High sampling frequency needed for digital • Implementation of hysteresis comparators. • High noise level at low speed [3]; A. Ameur is with Materials Laboratory (LeDMaScD), Amar Telidji University, BP 37G, Ghardaia Street, Laghouat, Algeria, (fax: +213 (0) 29 93 26 98); e-mail: amaissa1@ yahoo.fr). B. Mokhtari is with Materials Laboratory (LeDMaScD), Amar Telidji University, Laghouat, Algeria, e-mail: mokhtari71@ yahoo.fr). N. Essounbouli is with Center of Research in Science and Technologies of Information and Communication, Reims University, 10026 Troyes CEDEX, France. (e-mail: najib.essounbouli@univ-reims.fr). To overcome the above drawbacks, some researchers have been trying to propose solution to solve these problems by substitute hysteresis control by fuzzy control [4]. An effective modality for reducing the torque ripple without using a high sampling frequency is to calculate a proper reference voltage vector that can produce the desired torque and flux values, and then applied to the inverter using space vector modulation (SVM) [6]-[9]. This approach is known in the literature as DTC-SVM. Even though this control method provides fast torque response and small torque ripples. The high performance speed or position control requires an accurate knowledge of rotor shaft position and velocity in order to synchronize the phase excitation pulses to the rotor position. This implies the need for speed or a shaft position sensor such as an optical encoder or a resolver. However, the presence of this sensor (expensive and fragile and require special treatment of captured signals), causes several disadvantages from the standpoint of drive cost, encumbrance, reliability and noise problem [6]-[10]. To achieve sensorless operation of a PMSM drive, several algorithms have been suggested in recent literature. These methods can broadly be classified as: • Back-emf based estimators with explicit compensation for nonlinear properties, parameter variation and disturbances. • Estimation based on high frequency signal injection, exploiting the saliency property of a PMSM [3]. • Adaptive or robust observers based on advanced models. The Method of observers is sometimes more favourable due to its robustness to parameter variations and its excellent disturbance rejection capabilities[7]-[9]. This paper proposes the control strategy using space vector modulation (DTC-SVM) based on the MRAS (Model Reference Adaptive System) in the sensorless control of a permanent magnet synchronous motor and stator resistance estimation So that it can overcome the problem of sensitivity in the face of motor parameter variation. II. PMSM MODEL The stator and rotor flux equation of PMSM can be written in the reference frame of Park in the following form [2]:           +                     =           0 0 0 e sq sd q d q d i i L L φ φ φ (1) While the equations of the stator voltages are written in this same reference frame in the following form: Speed Sensorless Direct Torque Control of a PMSM Drive using Space Vector Modulation Based MRAS and Stator Resistance Estimator A. Ameur, B. Mokhtari, N. Essounbouli, L. Mokrani A World Academy of Science, Engineering and Technology International Journal of Electrical and Computer Engineering Vol:6, No:6, 2012 774 International Scholarly and Scientific Research & Innovation 6(6) 2012 ISNI:0000000091950263 Open Science Index, Electrical and Computer Engineering Vol:6, No:6, 2012 publications.waset.org/10388/pdf