Improved Sensorless Direct Torque Control Using Space Vector Modulation and Fuzzy Logic Controllers

Fast response, robust and simple structure of direct torque control (DTC) make it attractive in electric drive systems. Nonetheless, in sensorless applications, precise estimation of rotor speed and also motor torque and flux estimation are of utmost importance. An adaptive flux observer is presented considering stator current and flux vector components as state variables and rotor speed as an unknown parameter that is estimated simultaneously via an adaptive routine. Stator resistance value plays an important role in stator flux estimation. Similarly, stator resistance that is varying in different temperatures of motor can be updated through the adaptive scheme that provides more accurate performance of the system. Conversely, torque, flux, and current pulsations during steady state performance are disadvantages of the classical DTC method. A combined direct torque control and space vector modulation (DTC-SVM) strategy is presented using fuzzy logic control. Fuzzy logic controllers (FLCs) are designed such that obtain high accuracy during steady state, while preserve fast response in transients.