An improved direct torque control using fuzzy logic controllers and adaptive observer

Abstract

Simple structure, quick, and robust response of direct torque control (DTC) make it attractive in ac drives. However, in sensorless applications, precise estimation of rotor speed is a crucial issue as well as the torque and flux estimation. In this paper an adaptive flux observer is introduced with stator current and flux vector components as state variables and rotor speed as an unknown parameter which are estimated simultaneously using an adaptive scheme. Also torque, flux, and current pulsations during steady state are considered as the disadvantages of the classical DTC method. A combined DTC-SVM strategy is presented using fuzzy logic control (FLC). Fuzzy logic controllers are designed such that obtain a fast response for dynamic performance, and high accuracy in steady state.