An Improved Nonlinear Flux Observer Based Sensorless FOC IM Drive With Adaptive Predictive Current Control

This paper presents a novel adaptive predictive current controller (PCC) with improved flux estimator for a sensorless direct field oriented control (DFOC) induction motor (IM) drive. Classical PCC performance depends on the stator resistance of the motor which varies with temperature. In the proposed method, a discrete stator resistance estimator is developed to increase the robustness of the system toward stator resistance variations. An improved nonlinear discrete stator flux estimator is also developed to replace the pure integrator which reduces the initial value and dc offset problems. Sensorless operation of IM drive has advantages of reduced overall cost and increased reliability of motor operation. Dynamic and steady-state performances of the IM under different operating conditions are analyzed in MATLAB/Simulink as well as experimentally using dSPACE1104 controller and have been compared with conventional PCC. The simulation results of the classical and proposed methods are also validated experimentally. Smooth starting, reduced oscillations in speed and flux at low speed operation, fast speed and torque dynamics, robust operation of drive against load and variation in stator resistance, fast and smooth speed reversal are the main advantages of the proposed method over classical PCC-based DFOC IM drive.